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Nursing Math & Dosage Foundations · 500-Question Practice Bank (worked answers)

Weight-Based Safe Ranges, Part 1 — practice set (Q301–350)

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50 dosage-calculation problems (questions 301–350) with a full worked answer for each: dimensional-analysis setup, raw calculation, rounding rule, final labeled answer, rationale and clinical pearl. Work each one on paper first, then open the answer.

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50 review questions from the chapter. Try each one, then open the answer.

  1. Question 301. Scenario: A 6-year-old child weighing 44 lb is admitted with fever and mild throat pain following a tonsillectomy. Order: Acetaminophen 200 mg PO every 4 hours PRN for fever or pain. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert the child's weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 200 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Minimum safe dose: 10 mg/kg × 20 kg = 200 mg
    • Maximum safe dose: 15 mg/kg × 20 kg = 300 mg
    • Ordered dose: 200 mg per dose (PRN, no fixed daily total)
    • Comparison: 200 mg ≥ 200 mg and ≤ 300 mg
    • Conclusion: SAFE (exactly at the minimum) Setup (dimensional analysis): 20 kg × (10 mg / kg) = 200 mg (min); 20 kg × (15 mg / kg) = 300 mg (max) Raw calculation: 10 × 20 = 200 mg; 15 × 20 = 300 mg Rounding: No rounding needed (weight converted exactly to 20 kg). Final answer: SAFE; safe single-dose range 200–300 mg. Rationale: The ordered 200 mg equals the minimum safe single dose for a 20 kg child (10 mg/kg), so it is the lowest acceptable dose — still SAFE, though at the lower end of the range. Clinical pearl: When a dose lands exactly on the range boundary, it is still "within range" (inclusive) — but confirm the patient's actual weight and consider whether a higher, more therapeutic dose within the range would be more appropriate for symptom control.

  2. Question 302. Scenario: A 4-year-old child weighing 33 lb presents to the clinic with a fever of 102.4°F (39.1°C). Order: Ibuprofen 200 mg PO every 6 hours PRN for fever. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: UNSAFE — 200 mg/dose exceeds the maximum safe single dose. Safe-range check:

    • Converted weight: 33 lb ÷ 2.2 = 15 kg (exact, 15.0 kg)
    • Minimum safe dose: 5 mg/kg × 15 kg = 75 mg
    • Maximum safe dose: 10 mg/kg × 15 kg = 150 mg
    • Ordered dose: 200 mg per dose
    • Comparison: 200 mg > 150 mg (maximum)
    • Conclusion: UNSAFE (exceeds the maximum safe single dose) Setup (dimensional analysis): 15 kg × (5 mg / kg) = 75 mg (min); 15 kg × (10 mg / kg) = 150 mg (max) Raw calculation: 5 × 15 = 75 mg; 10 × 15 = 150 mg Rounding: No rounding needed. Final answer: UNSAFE; safe single-dose range is 75–150 mg; 200 mg is too high. Rationale: 200 mg for a 15 kg child equals 13.3 mg/kg, above the 10 mg/kg maximum. The dose should be held and clarified with the provider before administration. Clinical pearl: A common error is using an "adult-style" round number (200 mg) for a small child. Always recalculate the mg/kg dose, not just compare against what looks like a familiar tablet strength.

  3. Question 303. Scenario: A 2-year-old child weighing 22 lb is diagnosed with acute otitis media. Order: Amoxicillin 125 mg PO every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth) and evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 125 mg every 8 hours (375 mg/day) is within range. Safe-range check:

    • Converted weight: 22 lb ÷ 2.2 = 10 kg (exact, 10.0 kg)
    • Daily safe range: 20 mg/kg/day × 10 kg = 200 mg/day (min); 40 mg/kg/day × 10 kg = 400 mg/day (max)
    • Ordered dose: 125 mg per dose; 125 mg × 3 doses/day = 375 mg/day
    • Per-dose safe range: 200 mg/day ÷ 3 = 66.7 mg (min); 400 mg/day ÷ 3 = 133.3 mg (max)
    • Comparison: 375 mg/day ≤ 400 mg/day, and 125 mg/dose ≤ 133.3 mg/dose
    • Conclusion: SAFE Setup (dimensional analysis): 10 kg × (20 mg/kg/day) = 200 mg/day (min); 10 kg × (40 mg/kg/day) = 400 mg/day (max); 125 mg × 3 = 375 mg/day Raw calculation: 20 × 10 = 200 mg/day; 40 × 10 = 400 mg/day; 125 × 3 = 375 mg/day Rounding: No rounding needed. Final answer: SAFE; 375 mg/day is within the 200–400 mg/day safe range. Rationale: The total daily dose (375 mg) is within the safe daily range (200–400 mg), and each 125 mg dose is within the per-dose range (66.7–133.3 mg). Clinical pearl: For divided daily ranges, check BOTH the total daily dose and the individual dose. A daily total can look fine while one individual dose is out of range (or vice versa).

  4. Question 304. Scenario: An 11-month-old infant weighing 27.5 lb is febrile and irritable after immunizations. Order: Acetaminophen 160 mg PO every 4 hours PRN for fever. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 160 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 27.5 lb ÷ 2.2 = 12.5 kg (12.5 kg, exact to the tenth)
    • Minimum safe dose: 10 mg/kg × 12.5 kg = 125 mg
    • Maximum safe dose: 15 mg/kg × 12.5 kg = 187.5 mg
    • Ordered dose: 160 mg per dose
    • Comparison: 125 mg ≤ 160 mg ≤ 187.5 mg
    • Conclusion: SAFE Setup (dimensional analysis): 12.5 kg × (10 mg/kg) = 125 mg (min); 12.5 kg × (15 mg/kg) = 187.5 mg (max) Raw calculation: 10 × 12.5 = 125 mg; 15 × 12.5 = 187.5 mg Rounding: Weight 27.5 ÷ 2.2 = 12.5 kg (already at one decimal place). Final answer: SAFE; safe single-dose range 125–187.5 mg. Rationale: 160 mg falls between the minimum (125 mg) and maximum (187.5 mg) for a 12.5 kg infant, so it is safe to administer. Clinical pearl: Half-pound weights (e.g., 27.5 lb) produce clean kilogram values. Always divide by 2.2 — do not multiply by 2.2 or divide by 2.

  5. Question 305. Scenario: A nurse must verify a weight-based dose and first needs the child's weight in kilograms. Order: (No medication order — weight conversion only.) Available: N/A. Question: A child weighs 55 lb. Convert this weight to kilograms (1 kg ≈ 2.2 lb) and round to the nearest tenth. A) 24.0 kg B) 25.0 kg C) 25.9 kg D) 121 kg

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    Correct answer: B) 25.0 kg Setup (dimensional analysis): 55 lb × (1 kg / 2.2 lb) = 25 kg Raw calculation: 55 ÷ 2.2 = 25.0 Rounding: 25.0 kg (already a whole number; expressed to the nearest tenth). Final answer: 25.0 kg Rationale: Dividing pounds by 2.2 converts to kilograms. 55 ÷ 2.2 = 25 kg exactly. Clinical pearl: Always divide lb by 2.2 to get kg. Distractor C (25.9) comes from multiplying by 2.2 and mislabeling; distractor D (121) comes from multiplying 55 × 2.2 — the direction of the conversion must be checked.

  6. Question 306. Scenario: A 5-year-old child weighing 44 lb twisted an ankle at recess and has mild pain and swelling. Order: Ibuprofen 150 mg PO every 8 hours PRN for pain. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

    Show answer

    Correct answer: SAFE — 150 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Minimum safe dose: 5 mg/kg × 20 kg = 100 mg
    • Maximum safe dose: 10 mg/kg × 20 kg = 200 mg
    • Ordered dose: 150 mg per dose
    • Comparison: 100 mg ≤ 150 mg ≤ 200 mg
    • Conclusion: SAFE Setup (dimensional analysis): 20 kg × (5 mg/kg) = 100 mg (min); 20 kg × (10 mg/kg) = 200 mg (max) Raw calculation: 5 × 20 = 100 mg; 10 × 20 = 200 mg Rounding: No rounding needed. Final answer: SAFE; safe single-dose range 100–200 mg. Rationale: 150 mg is squarely within the 100–200 mg safe range for a 20 kg child. Clinical pearl: Ibuprofen's 5–10 mg/kg/dose range is roughly half of acetaminophen's 10–15 mg/kg/dose — do not interchange the two ranges.

  7. Question 307. Scenario: A 7-year-old child weighing 44 lb is admitted with a urinary tract infection. Order: Gentamicin 45 mg IV every 8 hours. Available: Gentamicin injection 40 mg/mL (hypothetical label). Question: Using a hypothetical educational range of gentamicin 2–2.5 mg/kg/dose every 8 hours, determine whether the ordered single dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 45 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Minimum safe dose: 2 mg/kg × 20 kg = 40 mg
    • Maximum safe dose: 2.5 mg/kg × 20 kg = 50 mg
    • Ordered dose: 45 mg per dose (every 8 hours)
    • Comparison: 40 mg ≤ 45 mg ≤ 50 mg
    • Conclusion: SAFE Setup (dimensional analysis): 20 kg × (2 mg/kg) = 40 mg (min); 20 kg × (2.5 mg/kg) = 50 mg (max) Raw calculation: 2 × 20 = 40 mg; 2.5 × 20 = 50 mg Rounding: No rounding needed. Final answer: SAFE; safe single-dose range 40–50 mg. Rationale: 45 mg is within the hypothetical 2–2.5 mg/kg/dose range (40–50 mg) for a 20 kg child. Clinical pearl: Aminoglycoside doses (like gentamicin) are weight-based and are typically verified against both per-dose and per-day limits; serum levels are monitored clinically. This hypothetical range is for practice only.

  8. Question 308. Scenario: A 12-year-old weighing 66 lb complains of a headache and low-grade fever. Order: Acetaminophen 325 mg PO every 4 hours PRN. Available: Acetaminophen tablet 325 mg. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 325 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 66 lb ÷ 2.2 = 30 kg (exact, 30.0 kg)
    • Minimum safe dose: 10 mg/kg × 30 kg = 300 mg
    • Maximum safe dose: 15 mg/kg × 30 kg = 450 mg
    • Ordered dose: 325 mg per dose
    • Comparison: 300 mg ≤ 325 mg ≤ 450 mg
    • Conclusion: SAFE Setup (dimensional analysis): 30 kg × (10 mg/kg) = 300 mg (min); 30 kg × (15 mg/kg) = 450 mg (max) Raw calculation: 10 × 30 = 300 mg; 15 × 30 = 450 mg Rounding: No rounding needed. Final answer: SAFE; safe single-dose range 300–450 mg. Rationale: A standard 325 mg tablet equals 10.8 mg/kg for a 30 kg child, within the 10–15 mg/kg range. Clinical pearl: Older children can approach "adult-sized" doses, but the mg/kg check still applies — an adult dose is only appropriate if it falls within the child's weight-based range.

  9. Question 309. Scenario: A 4-year-old child weighing 33 lb is diagnosed with streptococcal pharyngitis. Order: Amoxicillin 150 mg PO every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth) and evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 150 mg every 8 hours (450 mg/day) is within range. Safe-range check:

    • Converted weight: 33 lb ÷ 2.2 = 15 kg (exact, 15.0 kg)
    • Daily safe range: 20 mg/kg/day × 15 kg = 300 mg/day (min); 40 mg/kg/day × 15 kg = 600 mg/day (max)
    • Ordered dose: 150 mg per dose; 150 mg × 3 doses/day = 450 mg/day
    • Per-dose safe range: 300 mg/day ÷ 3 = 100 mg (min); 600 mg/day ÷ 3 = 200 mg (max)
    • Comparison: 450 mg/day ≤ 600 mg/day, and 100 mg ≤ 150 mg ≤ 200 mg
    • Conclusion: SAFE Setup (dimensional analysis): 15 kg × (20 mg/kg/day) = 300 mg/day (min); 15 kg × (40 mg/kg/day) = 600 mg/day (max); 150 mg × 3 = 450 mg/day Raw calculation: 20 × 15 = 300 mg/day; 40 × 15 = 600 mg/day; 150 × 3 = 450 mg/day Rounding: No rounding needed. Final answer: SAFE; 450 mg/day is within the 300–600 mg/day safe range. Rationale: Both the individual dose (150 mg) and the total daily dose (450 mg) fall within their respective safe ranges. Clinical pearl: When a range is stated "per day," always multiply the per-dose order by the number of daily doses to compare total-to-total.

  10. Question 310. Scenario: A nurse is preparing to administer a weight-based dose and must first convert the infant's weight. Order: (No medication order — weight conversion only.) Available: N/A. Question: An infant weighs 18 lb. Convert this weight to kilograms (1 kg ≈ 2.2 lb) and round to the nearest tenth. A) 8.0 kg B) 8.2 kg C) 8.18 kg D) 39.6 kg

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    Correct answer: B) 8.2 kg Setup (dimensional analysis): 18 lb × (1 kg / 2.2 lb) = 8.18 kg Raw calculation: 18 ÷ 2.2 = 8.1818… Rounding: Round to the nearest tenth: 8.1818… → 8.2 kg. Final answer: 8.2 kg Rationale: 18 ÷ 2.2 = 8.18 kg, which rounds to 8.2 kg to the nearest tenth. Clinical pearl: Only round the weight at the stated step; keep the unrounded value (8.1818…) for the dose calculation if precision matters.

  11. Question 311. Scenario: A 3-year-old child weighing 22 lb has a fever following a viral illness. Order: Ibuprofen 100 mg PO every 6 hours PRN for fever. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

    Show answer

    Correct answer: SAFE — 100 mg/dose is exactly at the maximum safe single dose. Safe-range check:

    • Converted weight: 22 lb ÷ 2.2 = 10 kg (exact, 10.0 kg)
    • Minimum safe dose: 5 mg/kg × 10 kg = 50 mg
    • Maximum safe dose: 10 mg/kg × 10 kg = 100 mg
    • Ordered dose: 100 mg per dose
    • Comparison: 100 mg = 100 mg (maximum)
    • Conclusion: SAFE (exactly at the maximum) Setup (dimensional analysis): 10 kg × (5 mg/kg) = 50 mg (min); 10 kg × (10 mg/kg) = 100 mg (max) Raw calculation: 5 × 10 = 50 mg; 10 × 10 = 100 mg Rounding: No rounding needed. Final answer: SAFE; safe single-dose range 50–100 mg; 100 mg is the maximum. Rationale: 100 mg equals 10 mg/kg — the top of the safe range — so it is safe but represents the largest acceptable single dose. Clinical pearl: A dose at the maximum boundary is safe once, but repeated maximum doses (every 6 hours) may reach or exceed daily limits — track the 24-hour total too.

  12. Question 312. Scenario: A 14-year-old weighing 88 lb has a fever and body aches. Order: Acetaminophen 500 mg PO every 4 hours PRN. Available: Acetaminophen tablet 500 mg. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), show the minimum and maximum safe single doses, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 500 mg/dose is within the safe range. Safe-range check:

    • Converted weight: 88 lb ÷ 2.2 = 40 kg (exact, 40.0 kg)
    • Minimum safe dose: 10 mg/kg × 40 kg = 400 mg
    • Maximum safe dose: 15 mg/kg × 40 kg = 600 mg
    • Ordered dose: 500 mg per dose
    • Comparison: 400 mg ≤ 500 mg ≤ 600 mg
    • Conclusion: SAFE Setup (dimensional analysis): 40 kg × (10 mg/kg) = 400 mg (min); 40 kg × (15 mg/kg) = 600 mg (max) Raw calculation: 10 × 40 = 400 mg; 15 × 40 = 600 mg Rounding: No rounding needed. Final answer: SAFE; safe single-dose range 400–600 mg. Rationale: 500 mg equals 12.5 mg/kg for a 40 kg child, within the 10–15 mg/kg range. Clinical pearl: Even at larger weights, verify against mg/kg — 500 mg is safe here, but the same 500 mg would be unsafe for a much smaller child.

  13. Question 313. Scenario: A 6-year-old child weighing 44 lb is prescribed cephalexin for a skin infection. Order: Cephalexin PO, divided every 6 hours (dose to be verified against a weight-based range). Available: Cephalexin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of cephalexin 25–50 mg/kg/day, what is the minimum safe TOTAL daily dose for this child? Convert weight to kg (round to the nearest tenth). A) 250 mg/day B) 500 mg/day C) 1,000 mg/day D) 2,000 mg/day

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    Correct answer: B) 500 mg/day Setup (dimensional analysis): 44 lb × (1 kg / 2.2 lb) = 20 kg; 20 kg × (25 mg/kg/day) = 500 mg/day Raw calculation: 44 ÷ 2.2 = 20 kg; 25 × 20 = 500 mg/day Rounding: No rounding needed. Final answer: 500 mg/day Rationale: The minimum safe daily dose is the lower bound of the range: 25 mg/kg/day × 20 kg = 500 mg/day. Clinical pearl: "Minimum safe total daily dose" means multiply by the LOWER number of the range (25 mg/kg/day), not the upper (50 mg/kg/day, which gives 1,000 mg/day — a distractor).

  14. Question 314. Scenario: A 5-year-old child weighing 40 lb is admitted with a fever of 103°F (39.4°C). Order: Acetaminophen 225 mg PO every 4 hours PRN for fever. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, first determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer and round to the nearest hundredth.

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    Correct answer: SAFE — 225 mg/dose; administer 7.03 mL. Safe-range check:

    • Converted weight: 40 lb ÷ 2.2 = 18.18 kg → 18.2 kg (nearest tenth)
    • Minimum safe dose: 10 mg/kg × 18.2 kg = 182 mg
    • Maximum safe dose: 15 mg/kg × 18.2 kg = 273 mg
    • Ordered dose: 225 mg per dose
    • Comparison: 182 mg ≤ 225 mg ≤ 273 mg
    • Conclusion: SAFE Setup (dimensional analysis): 225 mg × (5 mL / 160 mg) = 7.03125 mL Raw calculation: 225 ÷ 160 = 1.40625; 1.40625 × 5 = 7.03125 mL Rounding: Round to the nearest hundredth: 7.03125 → 7.03 mL. Final answer: SAFE; administer 7.03 mL. Rationale: 225 mg (≈12.4 mg/kg) is within the safe range, and the volume is calculated by canceling mg against the 160 mg/5 mL concentration. Clinical pearl: Apply the stated rounding rule (weight to the nearest tenth) first, then use that rounded weight consistently for the minimum and maximum dose — do not mix a rounded and an unrounded weight in the same problem.

  15. Question 315. Scenario: An 8-year-old child weighing 55 lb reports knee pain after playing soccer. Order: Ibuprofen 200 mg PO every 6 hours PRN for pain. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest tenth).

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    Correct answer: SAFE — 200 mg/dose; administer 10 mL. Safe-range check:

    • Converted weight: 55 lb ÷ 2.2 = 25 kg (exact, 25.0 kg)
    • Minimum safe dose: 5 mg/kg × 25 kg = 125 mg
    • Maximum safe dose: 10 mg/kg × 25 kg = 250 mg
    • Ordered dose: 200 mg per dose
    • Comparison: 125 mg ≤ 200 mg ≤ 250 mg
    • Conclusion: SAFE Setup (dimensional analysis): 200 mg × (5 mL / 100 mg) = 10 mL Raw calculation: 200 ÷ 100 = 2; 2 × 5 = 10 mL Rounding: No rounding needed (10.0 mL to the nearest tenth). Final answer: SAFE; administer 10 mL. Rationale: 200 mg (8 mg/kg) is within range, and the 100 mg/5 mL concentration yields exactly 10 mL. Clinical pearl: When the ordered dose is an exact multiple of the concentration strength, the volume comes out to a clean, easily measured amount.

  16. Question 316. Scenario: A 3-year-old child weighing 26.4 lb is diagnosed with acute otitis media. Order: Amoxicillin 80 mg PO every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). Evaluate BOTH the per-dose and per-day dose, and state SAFE or UNSAFE.

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    Correct answer: SAFE — 80 mg every 8 hours (240 mg/day) is exactly at the minimum safe daily dose. Safe-range check:

    • Converted weight: 26.4 lb ÷ 2.2 = 12 kg (exact, 12.0 kg)
    • Daily safe range: 20 mg/kg/day × 12 kg = 240 mg/day (min); 40 mg/kg/day × 12 kg = 480 mg/day (max)
    • Ordered dose: 80 mg per dose; 80 mg × 3 doses/day = 240 mg/day
    • Per-dose safe range: 240 mg/day ÷ 3 = 80 mg (min); 480 mg/day ÷ 3 = 160 mg (max)
    • Comparison: 240 mg/day = 240 mg/day (minimum), and 80 mg/dose = 80 mg (minimum)
    • Conclusion: SAFE (exactly at the minimum) Setup (dimensional analysis): 12 kg × (20 mg/kg/day) = 240 mg/day (min); 12 kg × (40 mg/kg/day) = 480 mg/day (max); 80 mg × 3 = 240 mg/day Raw calculation: 20 × 12 = 240 mg/day; 40 × 12 = 480 mg/day; 80 × 3 = 240 mg/day Rounding: No rounding needed. Final answer: SAFE; 240 mg/day is the minimum safe daily dose. Rationale: The total daily dose (240 mg) exactly equals the minimum (20 mg/kg/day), so it is safe but the lowest acceptable amount. Each 80 mg dose also equals the per-dose minimum. Clinical pearl: This question highlights per-dose vs per-day: 80 mg looks "small," but it correctly equals 20 mg/kg/day when given q8h. Verify the daily total, not just the single dose.

  17. Question 317. Scenario: A 7-year-old child weighing 44 lb is being treated for a skin infection. Order: Cephalexin 250 mg PO every 6 hours. Available: Cephalexin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of cephalexin 25–50 mg/kg/day (divided every 6 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), and evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 250 mg every 6 hours (1,000 mg/day) is exactly at the maximum safe daily dose. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Daily safe range: 25 mg/kg/day × 20 kg = 500 mg/day (min); 50 mg/kg/day × 20 kg = 1,000 mg/day (max)
    • Ordered dose: 250 mg per dose; 250 mg × 4 doses/day = 1,000 mg/day
    • Per-dose safe range: 500 mg/day ÷ 4 = 125 mg (min); 1,000 mg/day ÷ 4 = 250 mg (max)
    • Comparison: 1,000 mg/day = 1,000 mg/day (maximum), and 250 mg/dose = 250 mg (maximum)
    • Conclusion: SAFE (exactly at the maximum) Setup (dimensional analysis): 20 kg × (25 mg/kg/day) = 500 mg/day (min); 20 kg × (50 mg/kg/day) = 1,000 mg/day (max); 250 mg × 4 = 1,000 mg/day Raw calculation: 25 × 20 = 500 mg/day; 50 × 20 = 1,000 mg/day; 250 × 4 = 1,000 mg/day Rounding: No rounding needed. Final answer: SAFE; 1,000 mg/day is the maximum safe daily dose. Rationale: Giving 250 mg q6h totals 1,000 mg/day, which equals the upper bound (50 mg/kg/day) of the safe range. Clinical pearl: A q6h (four-times-daily) regimen multiplies a single dose by 4 — a common source of arithmetic error when a student multiplies by 3 instead.

  18. Question 318. Scenario: A 4-year-old child weighing 33 lb is diagnosed with acute otitis media and started on azithromycin. Order: Azithromycin 150 mg PO on day 1, then 75 mg PO daily on days 2 through 5. Available: Azithromycin oral suspension 200 mg/5 mL. Question: Using the well-known educational reference range of azithromycin 10 mg/kg on day 1, then 5 mg/kg/day on days 2–5, verify that BOTH the day-1 dose and the days 2–5 dose are safe. Convert weight to kg (round to the nearest tenth).

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    Correct answer: Both SAFE — day 1 = 150 mg; days 2–5 = 75 mg. Safe-range check:

    • Converted weight: 33 lb ÷ 2.2 = 15 kg (exact, 15.0 kg)
    • Day 1 target: 10 mg/kg × 15 kg = 150 mg → ordered 150 mg = 150 mg → SAFE
    • Days 2–5 target: 5 mg/kg × 15 kg = 75 mg → ordered 75 mg = 75 mg → SAFE Setup (dimensional analysis): 15 kg × (10 mg/kg) = 150 mg (day 1); 15 kg × (5 mg/kg) = 75 mg (days 2–5) Raw calculation: 10 × 15 = 150 mg; 5 × 15 = 75 mg Rounding: No rounding needed. Final answer: Both doses SAFE; 150 mg on day 1 and 75 mg on days 2–5. Rationale: Azithromycin uses a higher loading dose on day 1 (10 mg/kg) and a lower maintenance dose thereafter (5 mg/kg/day). Both ordered doses match the weight-based targets exactly. Clinical pearl: Two-phase dosing (loading vs maintenance) requires checking each phase against its own mg/kg target — a dose that is "safe" on day 1 may be wrong on days 2–5 (and vice versa).

  19. Question 319. Scenario: A 9-year-old child weighing 77 lb has severe menstrual cramping. Order: Ibuprofen 400 mg PO every 6 hours PRN. Available: Ibuprofen tablet 200 mg. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, what is the correct judgment of this order? Convert weight to kg (round to the nearest tenth). A) SAFE — the dose is within the safe range. B) UNSAFE — the dose exceeds the maximum safe single dose. C) SAFE — the dose is exactly at the maximum safe single dose. D) Cannot be determined without the serum creatinine.

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    Correct answer: B) UNSAFE — the dose exceeds the maximum safe single dose. Safe-range check:

    • Converted weight: 77 lb ÷ 2.2 = 35 kg (exact, 35.0 kg)
    • Minimum safe dose: 5 mg/kg × 35 kg = 175 mg
    • Maximum safe dose: 10 mg/kg × 35 kg = 350 mg
    • Ordered dose: 400 mg per dose
    • Comparison: 400 mg > 350 mg (maximum)
    • Conclusion: UNSAFE (exceeds the maximum safe single dose) Setup (dimensional analysis): 35 kg × (5 mg/kg) = 175 mg (min); 35 kg × (10 mg/kg) = 350 mg (max) Raw calculation: 5 × 35 = 175 mg; 10 × 35 = 350 mg Rounding: No rounding needed. Final answer: UNSAFE; safe single-dose range is 175–350 mg; 400 mg is too high. Rationale: 400 mg for a 35 kg child equals 11.4 mg/kg, above the 10 mg/kg maximum, so it is unsafe and must be clarified. Clinical pearl: Serum creatinine is not needed to decide this safety question — the mg/kg comparison alone shows the overdose. Don't be distracted by irrelevant distractor options.

  20. Question 320. Scenario: A 3-year-old child weighing 30.8 lb is admitted with a urinary tract infection. Order: Gentamicin 35 mg IV every 8 hours. Available: Gentamicin injection 40 mg/mL (hypothetical label). Syringes on hand: 1 mL, 3 mL, 5 mL. Question: Using a hypothetical educational single-dose target of gentamicin 2.5 mg/kg/dose, verify the ordered dose is correct (SAFE). Convert weight to kg (round to the nearest tenth). Then calculate the volume (mL) to draw up (round to the nearest hundredth) and select the most appropriate syringe.

    Show answer

    Correct answer: Dose correct (35 mg = 2.5 mg/kg); draw up 0.88 mL using a 1 mL syringe. Safe-range check:

    • Converted weight: 30.8 lb ÷ 2.2 = 14 kg (exact, 14.0 kg)
    • Target single dose: 2.5 mg/kg × 14 kg = 35 mg
    • Ordered dose: 35 mg per dose
    • Comparison: 35 mg = 35 mg → correct/SAFE Setup (dimensional analysis): 35 mg × (1 mL / 40 mg) = 0.875 mL Raw calculation: 35 ÷ 40 = 0.875 mL Rounding: Round to the nearest hundredth: 0.875 → 0.88 mL. Final answer: Draw up 0.88 mL in a 1 mL syringe. Rationale: The ordered 35 mg matches 2.5 mg/kg for 14 kg exactly, and the 40 mg/mL concentration requires a small (0.88 mL) volume, best measured with a 1 mL syringe for precision. Clinical pearl: Small critical-care volumes (under 1 mL) belong in a 1 mL (tuberculin) syringe, not a 3 mL or 5 mL syringe, to maintain dosing accuracy.

  21. Question 321. Scenario: A 6-year-old child weighing 47 lb has a fever and ear pain. Order: Acetaminophen 240 mg PO every 4 hours PRN. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest tenth).

    Show answer

    Correct answer: SAFE — 240 mg/dose; administer 7.5 mL. Safe-range check:

    • Converted weight: 47 lb ÷ 2.2 = 21.36 kg → 21.4 kg (nearest tenth)
    • Minimum safe dose: 10 mg/kg × 21.4 kg = 214 mg
    • Maximum safe dose: 15 mg/kg × 21.4 kg = 321 mg
    • Ordered dose: 240 mg per dose
    • Comparison: 214 mg ≤ 240 mg ≤ 321 mg
    • Conclusion: SAFE Setup (dimensional analysis): 240 mg × (5 mL / 160 mg) = 7.5 mL Raw calculation: 240 ÷ 160 = 1.5; 1.5 × 5 = 7.5 mL Rounding: No rounding needed (7.5 mL to the nearest tenth). Final answer: SAFE; administer 7.5 mL. Rationale: 240 mg (≈11.2 mg/kg) is within the safe range, and 160 mg/5 mL yields exactly 7.5 mL. Clinical pearl: 47 lb ÷ 2.2 = 21.36 kg rounds to 21.4 kg; apply the stated rounding rule to the weight, then carry that value through the rest of the problem.

  22. Question 322. Scenario: A 2-year-old child weighing 35.2 lb is diagnosed with acute sinusitis. Order: Amoxicillin-clavulanate 250 mg PO every 12 hours. Available: Amoxicillin-clavulanate oral suspension 200 mg/5 mL (amoxicillin component). Question: Using a hypothetical educational range of amoxicillin-clavulanate 25–45 mg/kg/day of the amoxicillin component (divided every 12 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), and evaluate the dose both per dose and per day.

    Show answer

    Correct answer: SAFE — 250 mg every 12 hours (500 mg/day) is within range. Safe-range check:

    • Converted weight: 35.2 lb ÷ 2.2 = 16 kg (exact, 16.0 kg)
    • Daily safe range: 25 mg/kg/day × 16 kg = 400 mg/day (min); 45 mg/kg/day × 16 kg = 720 mg/day (max)
    • Ordered dose: 250 mg per dose; 250 mg × 2 doses/day = 500 mg/day
    • Per-dose safe range: 400 mg/day ÷ 2 = 200 mg (min); 720 mg/day ÷ 2 = 360 mg (max)
    • Comparison: 400 mg/day ≤ 500 mg/day ≤ 720 mg/day, and 200 mg ≤ 250 mg ≤ 360 mg
    • Conclusion: SAFE Setup (dimensional analysis): 16 kg × (25 mg/kg/day) = 400 mg/day (min); 16 kg × (45 mg/kg/day) = 720 mg/day (max); 250 mg × 2 = 500 mg/day Raw calculation: 25 × 16 = 400 mg/day; 45 × 16 = 720 mg/day; 250 × 2 = 500 mg/day Rounding: No rounding needed. Final answer: SAFE; 500 mg/day is within the 400–720 mg/day safe range. Rationale: Both the per-dose (250 mg) and daily (500 mg) amounts fall within the hypothetical 25–45 mg/kg/day range for a 16 kg child. Clinical pearl: The amoxicillin-clavulanate range is expressed on the amoxicillin component — verify which component the range refers to before calculating.

  23. Question 323. Scenario: A 5-year-old child weighing 44 lb is diagnosed with streptococcal pharyngitis. Order: Penicillin V potassium 250 mg PO every 6 hours. Available: Penicillin V potassium oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of penicillin V 25–50 mg/kg/day (divided every 6 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), and evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 250 mg every 6 hours (1,000 mg/day) is exactly at the maximum safe daily dose. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Daily safe range: 25 mg/kg/day × 20 kg = 500 mg/day (min); 50 mg/kg/day × 20 kg = 1,000 mg/day (max)
    • Ordered dose: 250 mg per dose; 250 mg × 4 doses/day = 1,000 mg/day
    • Per-dose safe range: 500 mg/day ÷ 4 = 125 mg (min); 1,000 mg/day ÷ 4 = 250 mg (max)
    • Comparison: 1,000 mg/day = 1,000 mg/day (maximum), and 250 mg/dose = 250 mg (maximum)
    • Conclusion: SAFE (exactly at the maximum) Setup (dimensional analysis): 20 kg × (25 mg/kg/day) = 500 mg/day (min); 20 kg × (50 mg/kg/day) = 1,000 mg/day (max); 250 mg × 4 = 1,000 mg/day Raw calculation: 25 × 20 = 500 mg/day; 50 × 20 = 1,000 mg/day; 250 × 4 = 1,000 mg/day Rounding: No rounding needed. Final answer: SAFE; 1,000 mg/day is the maximum safe daily dose. Rationale: The ordered 250 mg q6h totals 1,000 mg/day, exactly the upper bound (50 mg/kg/day) of the safe range for penicillin V. Clinical pearl: Penicillin V and cephalexin share the 25–50 mg/kg/day reference range, but always confirm the specific drug's range rather than assuming.

  24. Question 324. Scenario: An 11-year-old weighing 66 lb has a fever and headache. Order: Acetaminophen 375 mg PO every 4 hours PRN. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), then determine how many mL to administer (round to the nearest tenth). A) 10 mL B) 11.7 mL C) 11.8 mL D) 23.4 mL

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    Correct answer: B) 11.7 mL Safe-range check (for completeness):

    • Converted weight: 66 lb ÷ 2.2 = 30 kg (exact, 30.0 kg)
    • Minimum safe dose: 10 mg/kg × 30 kg = 300 mg
    • Maximum safe dose: 15 mg/kg × 30 kg = 450 mg
    • Ordered dose: 375 mg per dose → 300 mg ≤ 375 mg ≤ 450 mg → SAFE Setup (dimensional analysis): 375 mg × (5 mL / 160 mg) = 11.71875 mL Raw calculation: 375 ÷ 160 = 2.34375; 2.34375 × 5 = 11.71875 mL Rounding: Round to the nearest tenth: 11.71875 → 11.7 mL. Final answer: 11.7 mL Rationale: 375 mg (12.5 mg/kg) is safe, and the volume 11.71875 mL rounds to 11.7 mL to the nearest tenth. Clinical pearl: Distractor C (11.8 mL) reflects rounding the intermediate 2.34 up before multiplying — keep the unrounded product until the final rounding step.

  25. Question 325. Scenario: A 6-year-old child weighing 48.4 lb has a fever and sore throat. Order: Ibuprofen 200 mg PO every 6 hours PRN. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer.

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    Correct answer: SAFE — 200 mg/dose; administer 10 mL. Safe-range check:

    • Converted weight: 48.4 lb ÷ 2.2 = 22 kg (exact, 22.0 kg)
    • Minimum safe dose: 5 mg/kg × 22 kg = 110 mg
    • Maximum safe dose: 10 mg/kg × 22 kg = 220 mg
    • Ordered dose: 200 mg per dose
    • Comparison: 110 mg ≤ 200 mg ≤ 220 mg
    • Conclusion: SAFE Setup (dimensional analysis): 200 mg × (5 mL / 100 mg) = 10 mL Raw calculation: 200 ÷ 100 = 2; 2 × 5 = 10 mL Rounding: No rounding needed. Final answer: SAFE; administer 10 mL. Rationale: 200 mg (9.1 mg/kg) is within range, and 100 mg/5 mL yields exactly 10 mL. Clinical pearl: 48.4 lb ÷ 2.2 = 22 kg exactly — such "clean" conversions come from weights that are even multiples of 2.2.

  26. Question 326. Scenario: A 5-year-old child weighing 39.6 lb is diagnosed with acute otitis media. Order: Cefdinir 126 mg PO every 12 hours. Available: Cefdinir oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of cefdinir 14 mg/kg/day (maximum 600 mg/day), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), and evaluate the total daily dose.

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    Correct answer: SAFE — 252 mg/day is exactly the target daily dose. Safe-range check:

    • Converted weight: 39.6 lb ÷ 2.2 = 18 kg (exact, 18.0 kg)
    • Target total daily dose: 14 mg/kg/day × 18 kg = 252 mg/day (well under the 600 mg/day cap)
    • Ordered dose: 126 mg per dose; 126 mg × 2 doses/day = 252 mg/day
    • Comparison: 252 mg/day = 252 mg/day → SAFE Setup (dimensional analysis): 18 kg × (14 mg/kg/day) = 252 mg/day; 126 mg × 2 = 252 mg/day Raw calculation: 14 × 18 = 252 mg/day; 126 × 2 = 252 mg/day Rounding: No rounding needed. Final answer: SAFE; 252 mg/day. Rationale: 126 mg twice daily equals 252 mg/day, which matches the 14 mg/kg/day reference for an 18 kg child. Clinical pearl: Cefdinir's 14 mg/kg/day is a single daily total — divide it by the dosing frequency (here 2) to find the per-dose amount, and watch the 600 mg/day maximum cap.

  27. Question 327. Scenario: A 3-year-old child weighing 26.4 lb is admitted with a febrile urinary tract infection. Order: Gentamicin 25 mg IV every 8 hours. Available: Gentamicin injection 40 mg/mL (hypothetical label). Question: Using a hypothetical educational range of gentamicin 5–7.5 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), and evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 25 mg every 8 hours (75 mg/day) is within range. Safe-range check:

    • Converted weight: 26.4 lb ÷ 2.2 = 12 kg (exact, 12.0 kg)
    • Daily safe range: 5 mg/kg/day × 12 kg = 60 mg/day (min); 7.5 mg/kg/day × 12 kg = 90 mg/day (max)
    • Ordered dose: 25 mg per dose; 25 mg × 3 doses/day = 75 mg/day
    • Per-dose safe range: 60 mg/day ÷ 3 = 20 mg (min); 90 mg/day ÷ 3 = 30 mg (max)
    • Comparison: 60 mg/day ≤ 75 mg/day ≤ 90 mg/day, and 20 mg ≤ 25 mg ≤ 30 mg
    • Conclusion: SAFE Setup (dimensional analysis): 12 kg × (5 mg/kg/day) = 60 mg/day (min); 12 kg × (7.5 mg/kg/day) = 90 mg/day (max); 25 mg × 3 = 75 mg/day Raw calculation: 5 × 12 = 60 mg/day; 7.5 × 12 = 90 mg/day; 25 × 3 = 75 mg/day Rounding: No rounding needed. Final answer: SAFE; 75 mg/day is within the 60–90 mg/day safe range. Rationale: Both the per-dose (25 mg) and daily (75 mg) amounts fall within the hypothetical 5–7.5 mg/kg/day range for a 12 kg child. Clinical pearl: A "per day" aminoglycoside range must be divided by the daily dosing frequency to check the individual dose — 25 mg alone can look small until you confirm it is within 20–30 mg/dose.

  28. Question 328. Scenario: A nurse has just administered a dose and now verifies it was appropriate. The child weighs 20 kg. Order (as administered): Ibuprofen 5 mL PO. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: How many milligrams of ibuprofen were delivered? Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, was the delivered dose SAFE? Show the minimum and maximum safe single doses.

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    Correct answer: 100 mg delivered; SAFE (exactly at the minimum). Safe-range check:

    • Weight: 20 kg (given)
    • Delivered dose: 5 mL × (100 mg / 5 mL) = 100 mg
    • Minimum safe dose: 5 mg/kg × 20 kg = 100 mg
    • Maximum safe dose: 10 mg/kg × 20 kg = 200 mg
    • Comparison: 100 mg = 100 mg (minimum) → SAFE Setup (dimensional analysis): 5 mL × (100 mg / 5 mL) = 100 mg Raw calculation: 100 ÷ 5 = 20 mg/mL; 20 × 5 = 100 mg Rounding: No rounding needed. Final answer: 100 mg delivered; SAFE (safe range 100–200 mg). Rationale: The 5 mL dose delivers 100 mg, which equals the 5 mg/kg minimum for a 20 kg child — safe, but the lowest acceptable dose. Clinical pearl: Reverse calculations (volume → mg) use the same dimensional-analysis method, just "backwards": multiply the volume by the concentration (mg/mL).

  29. Question 329. Scenario: A 10-year-old child weighing 66 lb is being treated for a MRSA skin infection. Order: Vancomycin IV, divided per institutional protocol (dose to be verified against a weight-based range). Available: Vancomycin injection (hypothetical label). Question: Using a hypothetical educational range of vancomycin 40–60 mg/kg/day, what is the maximum safe TOTAL daily dose for this child? Convert weight to kg (round to the nearest tenth). A) 1,200 mg/day B) 1,800 mg/day C) 2,400 mg/day D) 900 mg/day

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    Correct answer: B) 1,800 mg/day Setup (dimensional analysis): 66 lb × (1 kg / 2.2 lb) = 30 kg; 30 kg × (60 mg/kg/day) = 1,800 mg/day Raw calculation: 66 ÷ 2.2 = 30 kg; 60 × 30 = 1,800 mg/day Rounding: No rounding needed. Final answer: 1,800 mg/day Rationale: The maximum safe daily dose is the upper bound of the hypothetical 40–60 mg/kg/day range: 60 mg/kg/day × 30 kg = 1,800 mg/day. Clinical pearl: "Maximum safe daily dose" uses the TOP of the range (60 mg/kg/day); the minimum (40 mg/kg/day) gives 1,200 mg/day — a common distractor.

  30. Question 330. Scenario: A 4-year-old child weighing 26.4 lb is diagnosed with acute otitis media. Order: Amoxicillin 150 mg PO every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest tenth).

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    Correct answer: SAFE — 150 mg/dose; administer 3 mL. Safe-range check:

    • Converted weight: 26.4 lb ÷ 2.2 = 12 kg (exact, 12.0 kg)
    • Daily safe range: 20 mg/kg/day × 12 kg = 240 mg/day (min); 40 mg/kg/day × 12 kg = 480 mg/day (max)
    • Ordered dose: 150 mg per dose; 150 mg × 3 doses/day = 450 mg/day
    • Per-dose safe range: 240 mg/day ÷ 3 = 80 mg (min); 480 mg/day ÷ 3 = 160 mg (max)
    • Comparison: 450 mg/day ≤ 480 mg/day, and 80 mg ≤ 150 mg ≤ 160 mg
    • Conclusion: SAFE Setup (dimensional analysis): 150 mg × (5 mL / 250 mg) = 3 mL Raw calculation: 150 ÷ 250 = 0.6; 0.6 × 5 = 3 mL Rounding: No rounding needed (3.0 mL to the nearest tenth). Final answer: SAFE; administer 3 mL. Rationale: 150 mg q8h totals 450 mg/day, within the 240–480 mg/day range, and the 250 mg/5 mL concentration yields exactly 3 mL. Clinical pearl: The amoxicillin 250 mg/5 mL concentration gives a 3 mL volume for 150 mg — a clean, easily measured oral dose.

  31. Question 331. Scenario: A 13-year-old weighing 71.5 lb has a fever and headache. Order: Acetaminophen 480 mg PO every 4 hours PRN. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer.

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    Correct answer: SAFE — 480 mg/dose; administer 15 mL. Safe-range check:

    • Converted weight: 71.5 lb ÷ 2.2 = 32.5 kg (exact, 32.5 kg)
    • Minimum safe dose: 10 mg/kg × 32.5 kg = 325 mg
    • Maximum safe dose: 15 mg/kg × 32.5 kg = 487.5 mg
    • Ordered dose: 480 mg per dose
    • Comparison: 325 mg ≤ 480 mg ≤ 487.5 mg
    • Conclusion: SAFE Setup (dimensional analysis): 480 mg × (5 mL / 160 mg) = 15 mL Raw calculation: 480 ÷ 160 = 3; 3 × 5 = 15 mL Rounding: No rounding needed. Final answer: SAFE; administer 15 mL. Rationale: 480 mg (14.8 mg/kg) is within the safe range (close to but under the 487.5 mg maximum), and 160 mg/5 mL yields exactly 15 mL. Clinical pearl: 480 mg for a 32.5 kg child approaches the 15 mg/kg ceiling — always confirm the weight and consider the maximum when a dose sits near the top of the range.

  32. Question 332. Scenario: An 8-year-old child weighing 55 lb has a fever and sore throat. Order: Ibuprofen 250 mg PO every 8 hours PRN. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer.

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    Correct answer: SAFE — 250 mg/dose is exactly at the maximum; administer 12.5 mL. Safe-range check:

    • Converted weight: 55 lb ÷ 2.2 = 25 kg (exact, 25.0 kg)
    • Minimum safe dose: 5 mg/kg × 25 kg = 125 mg
    • Maximum safe dose: 10 mg/kg × 25 kg = 250 mg
    • Ordered dose: 250 mg per dose
    • Comparison: 250 mg = 250 mg (maximum) → SAFE Setup (dimensional analysis): 250 mg × (5 mL / 100 mg) = 12.5 mL Raw calculation: 250 ÷ 100 = 2.5; 2.5 × 5 = 12.5 mL Rounding: No rounding needed. Final answer: SAFE; administer 12.5 mL. Rationale: 250 mg equals the 10 mg/kg maximum for a 25 kg child, so it is safe but at the upper limit; the volume is 12.5 mL. Clinical pearl: A dose at the maximum is acceptable once, but note it is the ceiling — track the total daily intake to avoid exceeding the daily limit.

  33. Question 333. Scenario: A 6-year-old child weighing 48.4 lb is diagnosed with cellulitis. Order: Cephalexin 275 mg PO every 6 hours. Available: Cephalexin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of cephalexin 25–50 mg/kg/day (divided every 6 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest tenth).

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    Correct answer: SAFE — 275 mg/dose; administer 5.5 mL. Safe-range check:

    • Converted weight: 48.4 lb ÷ 2.2 = 22 kg (exact, 22.0 kg)
    • Daily safe range: 25 mg/kg/day × 22 kg = 550 mg/day (min); 50 mg/kg/day × 22 kg = 1,100 mg/day (max)
    • Ordered dose: 275 mg per dose; 275 mg × 4 doses/day = 1,100 mg/day
    • Per-dose safe range: 550 mg/day ÷ 4 = 137.5 mg (min); 1,100 mg/day ÷ 4 = 275 mg (max)
    • Comparison: 1,100 mg/day = 1,100 mg/day (maximum), and 275 mg/dose = 275 mg (maximum)
    • Conclusion: SAFE (exactly at the maximum) Setup (dimensional analysis): 275 mg × (5 mL / 250 mg) = 5.5 mL Raw calculation: 275 ÷ 250 = 1.1; 1.1 × 5 = 5.5 mL Rounding: No rounding needed (5.5 mL to the nearest tenth). Final answer: SAFE; administer 5.5 mL. Rationale: 275 mg q6h totals 1,100 mg/day, the exact upper bound of the 25–50 mg/kg/day range; the volume is 5.5 mL. Clinical pearl: A non-round dose like 275 mg still has a clean volume (5.5 mL) when the concentration divides evenly — don't assume an "odd" dose is automatically an error.

  34. Question 334. Scenario: A provider writes an order for a 3-year-old child weighing 22 lb with a fever. Order: Ibuprofen 400 mg PO every 6 hours PRN for fever. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Identify the error in this order. Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, state what the maximum safe single dose is for this child and explain what the nurse should do.

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    Correct answer: The order is in error — 400 mg exceeds the maximum safe single dose of 100 mg. The nurse should hold the dose and clarify with the provider. Safe-range check:

    • Converted weight: 22 lb ÷ 2.2 = 10 kg (exact, 10.0 kg)
    • Minimum safe dose: 5 mg/kg × 10 kg = 50 mg
    • Maximum safe dose: 10 mg/kg × 10 kg = 100 mg
    • Ordered dose: 400 mg per dose
    • Comparison: 400 mg > 100 mg (4× the maximum) → UNSAFE Setup (dimensional analysis): 10 kg × (5 mg/kg) = 50 mg (min); 10 kg × (10 mg/kg) = 100 mg (max) Raw calculation: 5 × 10 = 50 mg; 10 × 10 = 100 mg Rounding: No rounding needed. Final answer: Error identified; maximum safe single dose = 100 mg; hold and clarify. Rationale: 400 mg for a 10 kg child equals 40 mg/kg — four times the 10 mg/kg maximum. This is a potentially harmful overdose and must not be given. Clinical pearl: "Round-number" adult doses (400 mg ibuprofen) are a red flag for pediatric patients. The weight-based check should always be done before administering.

  35. Question 335. Scenario: A 4-year-old child weighing 36 lb has a fever. The suspension bottle label reads "Acetaminophen Oral Suspension 160 mg per 5 mL." Order: Acetaminophen 240 mg PO every 4 hours PRN. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer.

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    Correct answer: SAFE — 240 mg/dose; administer 7.5 mL. Safe-range check:

    • Converted weight: 36 lb ÷ 2.2 = 16.36 kg → 16.4 kg (nearest tenth)
    • Minimum safe dose: 10 mg/kg × 16.4 kg = 164 mg
    • Maximum safe dose: 15 mg/kg × 16.4 kg = 246 mg
    • Ordered dose: 240 mg per dose
    • Comparison: 164 mg ≤ 240 mg ≤ 246 mg
    • Conclusion: SAFE Setup (dimensional analysis): 240 mg × (5 mL / 160 mg) = 7.5 mL Raw calculation: 240 ÷ 160 = 1.5; 1.5 × 5 = 7.5 mL Rounding: No rounding needed. Final answer: SAFE; administer 7.5 mL. Rationale: Reading the label as "160 mg per 5 mL," the 240 mg dose is safe (≈14.6 mg/kg) and yields 7.5 mL. Clinical pearl: Label interpretation is the first step: identify the concentration (160 mg/5 mL = 32 mg/mL) before any calculation, and confirm the product is a suspension, not drops or tablets.

  36. Question 336. Scenario: A 2-year-old child weighing 22 lb has a fever of 103.1°F (39.5°C). Order: Acetaminophen 120 mg PO every 4 hours PRN for fever. Available: Acetaminophen oral suspension 160 mg/5 mL. Oral syringes on hand: 3 mL and 5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer and select the most appropriate syringe.

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    Correct answer: SAFE — 120 mg/dose; administer 3.75 mL using a 5 mL oral syringe. Safe-range check:

    • Converted weight: 22 lb ÷ 2.2 = 10 kg (exact, 10.0 kg)
    • Minimum safe dose: 10 mg/kg × 10 kg = 100 mg
    • Maximum safe dose: 15 mg/kg × 10 kg = 150 mg
    • Ordered dose: 120 mg per dose
    • Comparison: 100 mg ≤ 120 mg ≤ 150 mg
    • Conclusion: SAFE Setup (dimensional analysis): 120 mg × (5 mL / 160 mg) = 3.75 mL Raw calculation: 120 ÷ 160 = 0.75; 0.75 × 5 = 3.75 mL Rounding: No rounding needed. Final answer: SAFE; administer 3.75 mL in a 5 mL oral syringe. Rationale: 120 mg (12 mg/kg) is safe, and the volume is 3.75 mL. A 3 mL syringe cannot hold 3.75 mL, so a 5 mL syringe is required. Clinical pearl: Select a syringe one size larger than the volume — 3.75 mL exceeds a 3 mL syringe's capacity, so a 5 mL syringe is correct.

  37. Question 337. Scenario: A 6-year-old child weighing 44 lb has a high fever. Order: Ibuprofen 200 mg PO every 6 hours PRN for fever. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose (maximum 4 doses per 24 hours), what is the maximum safe TOTAL daily dose for this child? Convert weight to kg (round to the nearest tenth). A) 400 mg/day B) 600 mg/day C) 800 mg/day D) 1,000 mg/day

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    Correct answer: C) 800 mg/day Setup (dimensional analysis): 44 lb × (1 kg / 2.2 lb) = 20 kg; 20 kg × (10 mg/kg/dose) = 200 mg/dose; 200 mg × 4 doses = 800 mg/day Raw calculation: 44 ÷ 2.2 = 20 kg; 10 × 20 = 200 mg; 200 × 4 = 800 mg/day Rounding: No rounding needed. Final answer: 800 mg/day Rationale: The maximum safe single dose is 10 mg/kg × 20 kg = 200 mg; with a maximum of 4 doses per 24 hours, the maximum daily total is 200 × 4 = 800 mg/day. Clinical pearl: Maximum daily dose = (max mg/kg/dose × weight) × max doses per day. Be sure to multiply by the number of doses (4), not the mg/kg range's upper value alone.

  38. Question 338. Scenario: A 6-year-old child weighing 44 lb is diagnosed with pneumonia. Order: Amoxicillin 500 mg PO every 8 hours. Available: Amoxicillin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth), evaluate per dose and per day, and state what the nurse should do if the order is UNSAFE.

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    Correct answer: UNSAFE — 500 mg every 8 hours (1,500 mg/day) exceeds the maximum safe daily dose. Hold the dose and clarify with the provider. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Daily safe range: 20 mg/kg/day × 20 kg = 400 mg/day (min); 40 mg/kg/day × 20 kg = 800 mg/day (max)
    • Ordered dose: 500 mg per dose; 500 mg × 3 doses/day = 1,500 mg/day
    • Per-dose safe range: 400 mg/day ÷ 3 = 133.3 mg (min); 800 mg/day ÷ 3 = 266.7 mg (max)
    • Comparison: 1,500 mg/day > 800 mg/day (maximum), and 500 mg/dose > 266.7 mg/dose
    • Conclusion: UNSAFE (exceeds the maximum per dose AND per day) Setup (dimensional analysis): 20 kg × (20 mg/kg/day) = 400 mg/day (min); 20 kg × (40 mg/kg/day) = 800 mg/day (max); 500 mg × 3 = 1,500 mg/day Raw calculation: 20 × 20 = 400 mg/day; 40 × 20 = 800 mg/day; 500 × 3 = 1,500 mg/day Rounding: No rounding needed. Final answer: UNSAFE; hold and clarify with the provider before administration. Rationale: 500 mg q8h totals 1,500 mg/day (75 mg/kg/day), nearly double the 800 mg/day maximum. The nurse must not administer it and should contact the provider. Clinical pearl: When a dose is unsafe, the correct nursing action is to HOLD the medication and clarify — never "round down" or adjust a provider's order on your own.

  39. Question 339. Scenario: A provider has ordered a single dose of acetaminophen for a child but the chart weight is missing and must be reconstructed. Order: Acetaminophen 300 mg PO for one dose. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, for what range of weights (in kg) would a 300 mg dose be SAFE? Report the weight range.

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    Correct answer: SAFE for a weight range of 20 kg to 30 kg. Setup (dimensional analysis): Lower weight = 300 mg ÷ (15 mg/kg) = 20 kg; Upper weight = 300 mg ÷ (10 mg/kg) = 30 kg Raw calculation: 300 ÷ 15 = 20 kg; 300 ÷ 10 = 30 kg Rounding: No rounding needed. Final answer: 20–30 kg Rationale: At 20 kg, 300 mg equals 15 mg/kg (the maximum); at 30 kg, 300 mg equals 10 mg/kg (the minimum). Between these weights, 300 mg is within the 10–15 mg/kg range. Clinical pearl: To "reverse" a safe-range problem, divide the dose by each bound of the range: dose ÷ max mg/kg gives the lightest safe weight, and dose ÷ min mg/kg gives the heaviest.

  40. Question 340. Scenario: An 8-year-old child weighing 55 lb is being treated for a serious MRSA infection. Order: Vancomycin 10 mg/kg/dose IV for one dose (hypothetical single-dose order). Available: Vancomycin 500 mg vial reconstituted to 50 mg/mL (hypothetical label). Question: Convert weight to kg (round to the nearest tenth), calculate the ordered dose in mg, then calculate the volume (mL) to administer.

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    Correct answer: 250 mg; administer 5 mL. Setup (dimensional analysis): 55 lb × (1 kg / 2.2 lb) = 25 kg; 25 kg × (10 mg/kg) = 250 mg; 250 mg × (1 mL / 50 mg) = 5 mL Raw calculation: 55 ÷ 2.2 = 25 kg; 10 × 25 = 250 mg; 250 ÷ 50 = 5 mL Rounding: No rounding needed. Final answer: 250 mg; 5 mL. Rationale: The ordered 10 mg/kg/dose × 25 kg = 250 mg, and the hypothetical 50 mg/mL concentration yields 5 mL. Clinical pearl: Reconstituted vancomycin is commonly a 50 mg/mL concentration in practice settings, but always verify the actual vial label and dilution protocol for your institution.

  41. Question 341. Scenario: A 15-month-old infant weighing 15.4 lb is admitted with a urinary tract infection. Order: Gentamicin 2.5 mg/kg/dose IV every 8 hours (hypothetical order). Available: Gentamicin injection 40 mg/mL (hypothetical label). Syringes on hand: 1 mL, 3 mL, 5 mL. Question: Convert weight to kg (round to the nearest tenth), calculate the ordered dose in mg, then calculate the volume (mL) to draw up (round to the nearest hundredth) and select the most appropriate syringe.

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    Correct answer: 17.5 mg; draw up 0.44 mL using a 1 mL (tuberculin) syringe. Setup (dimensional analysis): 15.4 lb × (1 kg / 2.2 lb) = 7 kg; 7 kg × (2.5 mg/kg) = 17.5 mg; 17.5 mg × (1 mL / 40 mg) = 0.4375 mL Raw calculation: 15.4 ÷ 2.2 = 7 kg; 2.5 × 7 = 17.5 mg; 17.5 ÷ 40 = 0.4375 mL Rounding: Round to the nearest hundredth: 0.4375 → 0.44 mL. Final answer: 17.5 mg; draw up 0.44 mL in a 1 mL syringe. Rationale: The ordered dose is 2.5 mg/kg × 7 kg = 17.5 mg, and 40 mg/mL requires 0.44 mL — a sub-mL volume best drawn with a 1 mL syringe. Clinical pearl: Infants require tiny volumes; a 1 mL (tuberculin) syringe measures 0.44 mL far more accurately than a 3 mL or 5 mL syringe.

  42. Question 342. Scenario: A 4-year-old child weighing 33 lb has a fever. Order: Ibuprofen 150 mg PO every 6 hours PRN for fever. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose (maximum 4 doses per 24 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) per dose and the maximum total daily volume (mL).

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    Correct answer: SAFE — 150 mg/dose; 7.5 mL per dose; maximum 30 mL per 24 hours. Safe-range check:

    • Converted weight: 33 lb ÷ 2.2 = 15 kg (exact, 15.0 kg)
    • Minimum safe dose: 5 mg/kg × 15 kg = 75 mg
    • Maximum safe dose: 10 mg/kg × 15 kg = 150 mg
    • Ordered dose: 150 mg per dose → 150 mg = 150 mg (maximum) → SAFE Setup (dimensional analysis): 150 mg × (5 mL / 100 mg) = 7.5 mL/dose; 7.5 mL × 4 doses = 30 mL/day Raw calculation: 150 ÷ 100 = 1.5; 1.5 × 5 = 7.5 mL; 7.5 × 4 = 30 mL Rounding: No rounding needed. Final answer: SAFE; 7.5 mL per dose; maximum 30 mL per 24 hours. Rationale: 150 mg is the maximum safe single dose (10 mg/kg) for 15 kg, and 4 doses/day gives a 600 mg/day total, equal to 30 mL/day of the 100 mg/5 mL suspension. Clinical pearl: Track total daily volume for liquid medications — a child may exceed the daily mg limit even when each individual dose is "safe."

  43. Question 343. Scenario: A 3-year-old child weighing 12.3 kg is diagnosed with a skin infection. Order: Cephalexin 150 mg PO every 6 hours. Available: Cephalexin oral suspension 250 mg/5 mL. Question: Using the well-known educational reference range of cephalexin 25–50 mg/kg/day (divided every 6 hours), determine whether the ordered dose is SAFE. Evaluate the dose both per dose and per day.

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    Correct answer: SAFE — 150 mg every 6 hours (600 mg/day) is within range. Safe-range check:

    • Weight: 12.3 kg (given in kg — no conversion needed)
    • Daily safe range: 25 mg/kg/day × 12.3 kg = 307.5 mg/day (min); 50 mg/kg/day × 12.3 kg = 615 mg/day (max)
    • Ordered dose: 150 mg per dose; 150 mg × 4 doses/day = 600 mg/day
    • Per-dose safe range: 307.5 mg/day ÷ 4 = 76.9 mg (min); 615 mg/day ÷ 4 = 153.75 mg (max)
    • Comparison: 600 mg/day ≤ 615 mg/day, and 150 mg/dose ≤ 153.75 mg/dose
    • Conclusion: SAFE Setup (dimensional analysis): 12.3 kg × (25 mg/kg/day) = 307.5 mg/day (min); 12.3 kg × (50 mg/kg/day) = 615 mg/day (max); 150 mg × 4 = 600 mg/day Raw calculation: 25 × 12.3 = 307.5 mg/day; 50 × 12.3 = 615 mg/day; 150 × 4 = 600 mg/day Rounding: No rounding needed. Final answer: SAFE; 600 mg/day is within the 307.5–615 mg/day safe range. Rationale: When the weight is already in kilograms, skip the lb→kg conversion. The ordered 600 mg/day and 150 mg/dose are both within their respective safe ranges. Clinical pearl: Don't reflexively convert — check the units first. A weight already in kg should be used directly (and never divided by 2.2 again).

  44. Question 344. Scenario: A 10-year-old child weighing 66 lb is diagnosed with acute otitis media and prescribed high-strength amoxicillin. Order: Amoxicillin 600 mg PO every 12 hours. Available: Amoxicillin oral suspension 400 mg/5 mL (high-strength formulation). Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 12 hours), determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest tenth).

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    Correct answer: SAFE — 600 mg/dose is at the maximum; administer 7.5 mL. Safe-range check:

    • Converted weight: 66 lb ÷ 2.2 = 30 kg (exact, 30.0 kg)
    • Daily safe range: 20 mg/kg/day × 30 kg = 600 mg/day (min); 40 mg/kg/day × 30 kg = 1,200 mg/day (max)
    • Ordered dose: 600 mg per dose; 600 mg × 2 doses/day = 1,200 mg/day
    • Per-dose safe range: 600 mg/day ÷ 2 = 300 mg (min); 1,200 mg/day ÷ 2 = 600 mg (max)
    • Comparison: 1,200 mg/day = 1,200 mg/day (maximum), and 600 mg/dose = 600 mg (maximum)
    • Conclusion: SAFE (exactly at the maximum) Setup (dimensional analysis): 600 mg × (5 mL / 400 mg) = 7.5 mL Raw calculation: 600 ÷ 400 = 1.5; 1.5 × 5 = 7.5 mL Rounding: No rounding needed (7.5 mL to the nearest tenth). Final answer: SAFE; administer 7.5 mL. Rationale: 600 mg q12h totals 1,200 mg/day (40 mg/kg/day), the upper bound of the range; the high-strength 400 mg/5 mL suspension yields 7.5 mL. Clinical pearl: High-strength amoxicillin (400 mg/5 mL) delivers more drug per mL — using the standard 250 mg/5 mL calculation would give an incorrect, much larger volume.

  45. Question 345. Scenario: A 13-month-old infant weighing 13.2 lb is admitted with a febrile urinary tract infection. Order: Gentamicin 2 mg/kg/dose IV (hypothetical single-dose order). Available: Gentamicin injection 10 mg/mL (hypothetical label). Syringes on hand: 1 mL, 3 mL, 5 mL. Question: Convert weight to kg (round to the nearest tenth), calculate the ordered dose in mg, then calculate the volume (mL) to draw up and select the most appropriate syringe.

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    Correct answer: 12 mg; draw up 1.2 mL using a 3 mL syringe. Setup (dimensional analysis): 13.2 lb × (1 kg / 2.2 lb) = 6 kg; 6 kg × (2 mg/kg) = 12 mg; 12 mg × (1 mL / 10 mg) = 1.2 mL Raw calculation: 13.2 ÷ 2.2 = 6 kg; 2 × 6 = 12 mg; 12 ÷ 10 = 1.2 mL Rounding: No rounding needed. Final answer: 12 mg; draw up 1.2 mL in a 3 mL syringe. Rationale: The dose is 2 mg/kg × 6 kg = 12 mg, and 10 mg/mL yields 1.2 mL. Since 1.2 mL exceeds a 1 mL syringe's capacity, a 3 mL syringe is required. Clinical pearl: Syringe selection must account for capacity: a volume greater than 1 mL cannot be drawn in a 1 mL syringe — move up to a 3 mL syringe.

  46. Question 346. Scenario: A nurse reviews a handwritten order for a 44-lb child with a fever. Order: "Acetaminophen 320.0 mg PO q4h PRN for fever." Available: Acetaminophen oral suspension 160 mg/5 mL. Question: Identify the safety issue(s) in this order. Refer to The Joint Commission "Do Not Use" list where applicable, and use the well-known educational reference range of acetaminophen 10–15 mg/kg/dose to evaluate the dose (convert weight to kg, rounding to the nearest tenth). State what the nurse should do.

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    Correct answer: Two issues: (1) the trailing zero in "320.0 mg" violates The Joint Commission "Do Not Use" list; (2) 320 mg exceeds the maximum safe single dose of 300 mg. The nurse should clarify the order and hold the dose. Safe-range check:

    • Converted weight: 44 lb ÷ 2.2 = 20 kg (exact, 20.0 kg)
    • Minimum safe dose: 10 mg/kg × 20 kg = 200 mg
    • Maximum safe dose: 15 mg/kg × 20 kg = 300 mg
    • Ordered dose: 320 mg per dose
    • Comparison: 320 mg > 300 mg (maximum) → UNSAFE Setup (dimensional analysis): 20 kg × (15 mg/kg) = 300 mg (max); 320 mg ÷ 20 kg = 16 mg/kg Raw calculation: 15 × 20 = 300 mg; 320 ÷ 20 = 16 mg/kg Rounding: No rounding needed. Final answer: Trailing zero + overdose; hold and clarify. Rationale: "320.0 mg" contains a trailing zero, a Joint Commission "Do Not Use" error (risk of a ten-fold dosing error). Separately, 320 mg = 16 mg/kg, above the 15 mg/kg maximum. Both must be corrected before administration. Clinical pearl: Always scan orders for Do Not Use abbreviations/decimal practices (trailing zeros, missing leading zeros) AND independently verify the mg/kg dose — a single order can contain more than one error.

  47. Question 347. Scenario: A nurse has just administered a dose and is now checking it. The child weighs 22 lb. Order (as administered): Acetaminophen 7.5 mL PO. Available: Acetaminophen oral suspension 160 mg/5 mL. Question: How many milligrams of acetaminophen were delivered? Using the well-known educational reference range of acetaminophen 10–15 mg/kg/dose, was the delivered dose SAFE? Convert weight to kg (round to the nearest tenth) and show the minimum and maximum safe single doses.

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    Correct answer: 240 mg delivered; UNSAFE (overdose — exceeds the maximum safe single dose of 150 mg). Safe-range check:

    • Converted weight: 22 lb ÷ 2.2 = 10 kg (exact, 10.0 kg)
    • Delivered dose: 7.5 mL × (160 mg / 5 mL) = 240 mg
    • Minimum safe dose: 10 mg/kg × 10 kg = 100 mg
    • Maximum safe dose: 15 mg/kg × 10 kg = 150 mg
    • Comparison: 240 mg > 150 mg (maximum) → UNSAFE Setup (dimensional analysis): 7.5 mL × (160 mg / 5 mL) = 240 mg Raw calculation: 160 ÷ 5 = 32 mg/mL; 32 × 7.5 = 240 mg Rounding: No rounding needed. Final answer: 240 mg delivered; UNSAFE (24 mg/kg, above the 15 mg/kg maximum). Rationale: The administered volume delivers 240 mg, which is 24 mg/kg for a 10 kg child — well above the 15 mg/kg maximum. This is a potentially hepatotoxic overdose of acetaminophen and must be reported immediately. Clinical pearl: Acetaminophen overdose is a leading cause of acute liver failure — when a reverse check reveals an unsafe delivered dose, escalate per policy (notify provider, follow antidote protocol).

  48. Question 348. Scenario: A 6-year-old child weighing 48.4 lb has a fever and sore throat. Order: Ibuprofen 165 mg PO every 6 hours PRN. Available: Ibuprofen oral suspension 100 mg/5 mL. Question: Using the well-known educational reference range of ibuprofen 5–10 mg/kg/dose, determine whether the ordered dose is SAFE. Convert weight to kg (round to the nearest tenth). If safe, calculate the volume (mL) to administer (round to the nearest hundredth).

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    Correct answer: SAFE — 165 mg/dose; administer 8.25 mL. Safe-range check:

    • Converted weight: 48.4 lb ÷ 2.2 = 22 kg (exact, 22.0 kg)
    • Minimum safe dose: 5 mg/kg × 22 kg = 110 mg
    • Maximum safe dose: 10 mg/kg × 22 kg = 220 mg
    • Ordered dose: 165 mg per dose
    • Comparison: 110 mg ≤ 165 mg ≤ 220 mg
    • Conclusion: SAFE Setup (dimensional analysis): 165 mg × (5 mL / 100 mg) = 8.25 mL Raw calculation: 165 ÷ 100 = 1.65; 1.65 × 5 = 8.25 mL Rounding: Round to the nearest hundredth: 8.25 mL (already exact). Final answer: SAFE; administer 8.25 mL. Rationale: 165 mg (7.5 mg/kg) is within range, and the 100 mg/5 mL concentration yields 8.25 mL. Clinical pearl: A 7.5 mg/kg dose sits at the midpoint of ibuprofen's 5–10 mg/kg range — an example of a "therapeutic middle" rather than a boundary dose.

  49. Question 349. Scenario: A 2-year-old child weighing 35.2 lb is diagnosed with acute otitis media. Order: Amoxicillin 175 mg PO every 8 hours. Available: Amoxicillin oral suspension 125 mg/5 mL. Question: Using the well-known educational reference range of amoxicillin 20–40 mg/kg/day (divided every 8 hours), complete the full 7-step safe-dose check: convert weight to kg (round to the nearest tenth), calculate the minimum and maximum safe doses (per dose and per day), compare the ordered dose, state SAFE or UNSAFE, and if safe calculate the volume (mL) to administer (round to the nearest tenth).

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    Correct answer: SAFE — 175 mg every 8 hours (525 mg/day) is within range; administer 7 mL. Full 7-step safe-dose check:

    1. Convert weight: 35.2 lb ÷ 2.2 = 16 kg (exact, 16.0 kg)
    2. Daily safe range: 20 mg/kg/day × 16 kg = 320 mg/day (min); 40 mg/kg/day × 16 kg = 640 mg/day (max)
    3. Per-dose safe range: 320 mg/day ÷ 3 = 106.7 mg (min); 640 mg/day ÷ 3 = 213.3 mg (max)
    4. Ordered dose: 175 mg per dose; 175 mg × 3 doses/day = 525 mg/day
    5. Doses/day: 3 (every 8 hours)
    6. Comparison: 320 mg/day ≤ 525 mg/day ≤ 640 mg/day, and 106.7 mg ≤ 175 mg ≤ 213.3 mg
    7. Conclusion: SAFE Setup (dimensional analysis): 175 mg × (5 mL / 125 mg) = 7 mL Raw calculation: 175 ÷ 125 = 1.4; 1.4 × 5 = 7 mL Rounding: No rounding needed (7.0 mL to the nearest tenth). Final answer: SAFE; administer 7 mL. Rationale: Both the per-dose (175 mg) and daily (525 mg) amounts fall within the safe range for a 16 kg child, and the 125 mg/5 mL concentration yields exactly 7 mL. Clinical pearl: The 7-step workflow (convert → per-dose vs per-day → min → max → doses/day → compare → SAFE/UNSAFE, then volume) prevents the most common pediatric errors: wrong conversion, per-dose/per-day confusion, and skipping the range check before dosing.

  50. Question 350. Scenario: An 11-year-old child weighing 66 lb is admitted with a serious MRSA infection. Order: Vancomycin 15 mg/kg/dose IV every 8 hours. Available: Vancomycin 500 mg vial reconstituted to 50 mg/mL (hypothetical label). Question: Using a hypothetical educational range of vancomycin 40–60 mg/kg/day (divided every 8 hours), complete the full 7-step safe-dose check: convert weight to kg (round to the nearest tenth), calculate the minimum and maximum safe doses (per dose and per day), compare the ordered dose, state SAFE or UNSAFE, and if safe calculate the volume (mL) per dose (round to the nearest tenth).

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    Correct answer: SAFE — 450 mg every 8 hours (1,350 mg/day) is within range; administer 9 mL per dose. Full 7-step safe-dose check:

    1. Convert weight: 66 lb ÷ 2.2 = 30 kg (exact, 30.0 kg)
    2. Daily safe range: 40 mg/kg/day × 30 kg = 1,200 mg/day (min); 60 mg/kg/day × 30 kg = 1,800 mg/day (max)
    3. Per-dose safe range: 1,200 mg/day ÷ 3 = 400 mg (min); 1,800 mg/day ÷ 3 = 600 mg (max)
    4. Ordered dose: 15 mg/kg × 30 kg = 450 mg per dose; 450 mg × 3 doses/day = 1,350 mg/day
    5. Doses/day: 3 (every 8 hours)
    6. Comparison: 1,200 mg/day ≤ 1,350 mg/day ≤ 1,800 mg/day, and 400 mg ≤ 450 mg ≤ 600 mg
    7. Conclusion: SAFE Setup (dimensional analysis): 30 kg × (15 mg/kg/dose) = 450 mg/dose; 450 mg × (1 mL / 50 mg) = 9 mL Raw calculation: 15 × 30 = 450 mg; 450 × 3 = 1,350 mg/day; 450 ÷ 50 = 9 mL Rounding: No rounding needed (9.0 mL to the nearest tenth). Final answer: SAFE; administer 9 mL per dose. Rationale: The ordered 15 mg/kg/dose × 30 kg = 450 mg q8h totals 1,350 mg/day (45 mg/kg/day), within the hypothetical 40–60 mg/kg/day range; the 50 mg/mL concentration yields 9 mL per dose. Clinical pearl: Vancomycin dosing requires BOTH a per-dose mg/kg target and a total daily mg/kg check — a dose can satisfy one but violate the other, so always verify both.

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