Common Antidotes

The General Approach Comes First

Before any antidote is considered, the poisoned patient gets the same systematic evaluation as any critically ill patient: Airway, Breathing, Circulation, Disability, Exposure. Airway protection and adequate oxygenation prevent hypoxic injury regardless of the poison involved; circulatory support with fluids and, when needed, vasopressors buys time for the body or an antidote to work. Most fatal outcomes in poisoning come from complications of the exposure — aspiration, respiratory failure, arrhythmia, seizure — rather than from a missing antidote. Supportive care is the single most reliable life-saving intervention in toxicology, full stop.

Two checks belong to essentially every case of altered mental status: a rapid glucose measurement, because hypoglycemia mimics and worsens almost any toxidrome and is instantly correctable, and consideration of naloxone, because opioid toxicity is common, under-recognized, and rapidly reversible. Thiamine is considered in patients with suspected alcohol use disorder or malnutrition before or alongside glucose, to reduce the risk of precipitating a thiamine-deficiency encephalopathy.

Toxidromes as a Diagnostic Shortcut

When the ingested substance is unknown, clinicians rely on toxidromes — clusters of vital sign and exam findings that point toward a class of toxin before any lab result returns. Recognizing a sympathomimetic, anticholinergic, cholinergic, opioid, or sedative-hypnotic picture allows early, targeted decisions about monitoring and treatment while the specific agent is confirmed. Toxidrome recognition is a clinical reasoning shortcut, not a substitute for history, collateral information, and confirmatory testing.

Poison Control and Decontamination

A regional poison control center should be used early and often; it provides real-time, substance-specific guidance. Gastrointestinal decontamination has a narrow modern role. Activated charcoal binds many drugs within the gut lumen and is most useful soon after ingestion of a charcoal-adsorbable substance in a patient who can protect their airway; it is not useful for most caustics, alcohols, metals, or hydrocarbons, and its benefit shrinks quickly with time. Whole bowel irrigation flushes the gastrointestinal tract with a non-absorbed solution and is reserved for large ingestions of extended-release or enteric-coated formulations, or ingested drug packets, where charcoal alone is insufficient. Enhanced elimination — urinary alkalinization, which favors excretion of certain acidic drugs, and hemodialysis, which removes small, water-soluble, poorly protein-bound toxins from blood — is reserved for specific toxins and severe or refractory cases.

Antidote Pairings

The table below organizes the antidote-toxin pairs covered across this topic without specifying doses.

Several pairings carry caveats. Flumazenil can precipitate seizures in benzodiazepine-dependent patients or those who co-ingested a pro-convulsant, so it is used selectively. Methylene blue is avoided or used cautiously in G6PD deficiency, since it can trigger hemolysis, and it interacts dangerously with serotonergic drugs, where it can precipitate serotonin syndrome. Glucagon, calcium, and high-dose insulin are often combined in beta blocker and calcium channel blocker toxicity because they act through complementary mechanisms. Sodium bicarbonate serves two purposes — narrowing sodium-channel blockade in tricyclic and related toxicity, and enhancing renal salicylate elimination through urinary alkalinization. Physostigmine is reserved for severe, confirmed antimuscarinic toxicity because it carries its own risk of cholinergic excess. Fomepizole and ethanol both block the enzyme that converts methanol and ethylene glycol into toxic metabolites, and dialysis is added when toxic metabolites or severe acidosis are already present.

The unifying lesson: antidotes are targeted tools layered on top of supportive care, not replacements for it, and using the right one depends on accurate diagnosis first.