Pharmacology for Nurses · Anti-infective Drugs
Introduction to Sexually Transmitted Infections and Drugs to Treat Them
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In 30 seconds
Sexually transmitted infections (STIs) are infections passed primarily through sexual contact, and they are caused by every major pathogen type: bacteria (chlamydia, gonorrhea, syphilis), viruses (herpes simplex virus, human papillomavirus, HIV, hepatitis B), protozoa (trichomoniasis), and ectoparasites (pubic lice). What unites them for pharmacology is a simple idea: treatment depends on the pathogen type, and prevention depends on interrupting transmission — through vaccination (HPV, hepatitis B), barrier methods, testing, and partner treatment.
Some STIs are curable with a short course of antimicrobials (most bacterial and protozoal infections); others are manageable but not curable (viral infections such as herpes and HIV, which are suppressed rather than eliminated). This distinction shapes every conversation the nurse has: a person with chlamydia can expect a cure and retesting to confirm it; a person with herpes needs education about episodic or suppressive therapy and about transmission risk between outbreaks.
Many STIs are asymptomatic — chlamydia and gonorrhea in particular can silently damage the reproductive tract, causing pelvic inflammatory disease, ectopic pregnancy, and infertility. Because people often feel fine, screening is what finds these infections, and nurses play a central role in offering testing, normalizing it, and treating it without judgment.
Why this matters
STIs are among the most common reportable infections worldwide, and their complications — infertility, chronic pelvic pain, congenital infections, HPV-related cancer, and enhanced HIV transmission — are largely preventable. For nurses: screening saves fertility and lives; pharmacology varies by organism (bacterial vs. viral vs. protozoal); special populations need special care (pregnancy changes drug selection, and newborns can acquire infections during delivery); and communication is a clinical skill, because stigma is the biggest barrier to testing and treatment. Exam questions frequently test the bacterial-vs-viral treatment distinction and the "treat partners + retest" follow-up.
The college version
Core Concepts
Bacterial STIs and their drug classes (mechanisms only)
- Chlamydia (Chlamydia trachomatis) is often asymptomatic; untreated, it can ascend to cause pelvic inflammatory disease. Treatment uses a macrolide or tetracycline antibiotic, which inhibit bacterial protein synthesis.
- Gonorrhea (Neisseria gonorrhoeae) causes urethritis and cervicitis and frequently co-infects with chlamydia. Its growing Antimicrobial resistance Pathogens no longer killed by drugs that once worked Full entry → is a major public health concern — current guidelines, not habit, must drive drug selection.
- Syphilis (Treponema pallidum) is a multi-stage infection: primary (painless chancre), secondary (rash), latent (silent), and tertiary (heart, brain, and organ damage years later). Penicillins, which disrupt bacterial cell wall synthesis, are the cornerstone; the stage determines the regimen.
The general principle: bacterial STIs are curable, but the correct drug, dose, and duration must come from current guidelines because resistance patterns change.
Viral STIs: suppression and prevention
- Herpes simplex virus (HSV) causes recurrent genital lesions. Nucleoside-analogue antivirals (which inhibit viral DNA polymerase) shorten and prevent outbreaks, but they do not eliminate the virus, which persists in nerve ganglia; people can shed virus without visible lesions.
- Human papillomavirus (HPV) usually clears on its own, but persistent high-risk types can cause cervical, anal, and oropharyngeal cancers. There is no cure — the prevention is vaccination, most effective before exposure.
- Hepatitis B is vaccine-preventable and managed with antivirals when chronic. HIV (previous topic) is managed with combination ART, which also reduces sexual transmission.
Protozoal and ectoparasitic STIs
Trichomoniasis (Trichomonas vaginalis) causes vaginitis with discharge and itching and is treated with antiprotozoal drugs; partners are treated to prevent reinfection. Pubic lice and scabies are treated with topical (sometimes oral) anti-parasitic agents, with close contacts and bedding handled to prevent reinfestation.
Screening, partner treatment, and the "ping-pong" problem
Treating only one person in a pair guarantees reinfection — the partner reinfects them and the cycle continues. Partner notification Informing and treating sexual partners of an infected person Full entry → and treatment, including Expedited partner therapy Providing treatment for partners without an individual exam, where permitted Full entry → where permitted by law, is core STI Infection transmitted primarily through sexual contact Full entry → management. Nurses also enforce follow-up: some infections require a Test of cure Lab testing confirming infection is cleared after treatment Full entry →, and people should abstain from sex until treatment is complete per the regimen. Many STIs are reportable to public health; nurses follow jurisdictional reporting policy.
Pregnancy and congenital infection
STIs in pregnancy can harm the fetus or newborn — congenital syphilis, eye infection from gonorrhea or chlamydia during delivery, severe neonatal HSV. Routine prenatal screening exists for this reason, and drug selection in pregnancy weighs benefit against fetal risk, always per current obstetric guidelines and prescriber orders.
Common Confusions
| Do Not Confuse | With | Difference |
|---|---|---|
| Chlamydia | Gonorrhea | Different bacteria with different recommended treatments — but they often co-occur, so treatment frequently covers both |
| Bacterial STI | Viral STI | Bacterial (chlamydia, gonorrhea, syphilis) are curable with antibiotics; viral (HSV, HPV, HIV) are suppressed or prevented, not cured |
| Latent syphilis | Not infected | Latent means present but silent — it can still progress to tertiary syphilis |
| HSV suppressive therapy | HSV cure | Suppressive antivirals reduce outbreaks and transmission but never eliminate the virus |
| HPV infection | Cervical cancer | Most HPV clears on its own; only persistent high-risk infection can progress to cancer |
| Treating the patient only | Treating patient and partners | Single-person treatment fails when partners reinfect — partner treatment is part of the plan |
| Any antibiotic | The guideline-recommended antibiotic | Resistance and efficacy vary; selection follows current guidelines and local resistance data |
Eli explains
The same idea, in plain words
Explain it like I’m 10
Some germs that spread between people who are close can make them sick. If the germ is a bacterium, medicine can kill it completely — like spraying weed killer on a weed. If the germ is a virus, medicine can't always remove it, but it can keep it quiet, like locking a noisy dog in a soundproof room. The best trick of all is a vaccine, which teaches your body to defeat the germ before it ever arrives.
Worked example
A 22-year-old person visits a clinic for a routine checkup with no symptoms. The nurse takes a sexual health history in a neutral, matter-of-fact way and offers STI screening, which the person accepts. Results return positive for chlamydia; gonorrhea, syphilis, and HIV are negative. The nurse's teaching covers three things. First, the treatment plan: a prescribed antibiotic course taken exactly as ordered, even though the person feels fine, because untreated chlamydia can ascend and damage the reproductive tract. Second, the "ping-pong" rule: sexual partners need evaluation and treatment too, or the person will simply be reinfected; the clinic offers partner services and discusses expedited partner therapy where permitted. Third, follow-up: avoid sexual contact until treatment is complete, and return for repeat testing to confirm cure. Nothing about this scenario was dramatic — that is the point. Most STI care is quiet, routine, and completely effective when the nurse normalizes testing, teaches the treatment logic, and manages the partner piece.
Key takeaways
- Know the pathogen type first: bacterial/protozoal STIs are curable; viral STIs are suppressed or prevented.
- Chlamydia and gonorrhea are often silent — screening, not symptoms, finds them; untreated, they cause pelvic inflammatory disease and infertility.
- Co-infection is common: gonorrhea treatment frequently covers chlamydia; test for HIV and syphilis in anyone diagnosed with an STI.
- Syphilis staging matters: primary → secondary → latent → tertiary; the stage drives the regimen, and untreated syphilis damages the heart and brain.
- Antimicrobial resistance is a live threat (especially gonorrhea) — follow current guidelines.
- HPV and hepatitis B are vaccine-preventable; HSV antivirals suppress, don't cure.
- Treat the partners: reinfection ("ping-pong") defeats single-person treatment.
- Pregnancy changes drug selection — follow obstetric guidelines; congenital infection is preventable with screening.
- Person-first, nonjudgmental care is how nurses get people to test and stay in care.
Check yourself
6 review questions from the chapter. Try each one, then open the answer.
Why can bacterial STIs be cured while viral STIs generally cannot?
Show answer
Bacteria have metabolic machinery antimicrobials can selectively disrupt, killing them. Viruses hide inside human cells, so antivirals suppress replication rather than eliminate the virus; some viral infections are best prevented by vaccination.
A person tests positive for gonorrhea. Why might treatment also cover chlamydia, and why offer HIV and syphilis testing?
Show answer
Gonorrhea and chlamydia frequently co-infect, so coverage of both is standard per current guidelines. STI co-infection is common, and HIV/syphilis screening is recommended for anyone diagnosed with an STI.
What are the four stages of syphilis, and why does the stage matter?
Show answer
Primary (chancre), secondary (rash), latent (silent), tertiary (organ damage). The stage reflects duration and guides the regimen and follow-up per current syphilis guidelines.
What is the "ping-pong" problem, and how do partner services address it?
Show answer
If only one partner is treated, the other reinfects them. Partner notification, treatment of contacts, and (where permitted) expedited partner therapy break the cycle — always per law and institutional policy.
Why is HPV "treated" with a vaccine rather than a drug?
Show answer
HPV is a virus no drug eliminates once established. The vaccine trains the immune system to neutralize it before infection, which is why it is given before exposure.
Why does pregnancy change STI drug selection?
Show answer
Some drugs are avoided or adjusted because of fetal risk, while untreated infections can harm the fetus or newborn. Drug selection follows current obstetric guidelines and prescriber orders.
Study tools & related lessonsKey vocabulary · Related
Key vocabulary
- STI
- Infection transmitted primarily through sexual contact
- Asymptomatic infection
- Infection with no noticeable symptoms
- Pelvic inflammatory disease (PID)
- Ascending infection of the female reproductive tract
- Antimicrobial resistance
- Pathogens no longer killed by drugs that once worked
- Nucleoside analogue antiviral
- Drug mimicking a building block and halting viral DNA copying
- Test of cure
- Lab testing confirming infection is cleared after treatment
- Partner notification
- Informing and treating sexual partners of an infected person
- Congenital infection
- Infection passed from parent to fetus or newborn
- Expedited partner therapy
- Providing treatment for partners without an individual exam, where permitted
Sources & references
This lesson was adapted from the open educational references above; their licenses and attributions are preserved. See Copyright & Licensing.
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