Toxicology / Antidote Reference

Poison Control: 1-800-222-1222 — available 24/7 nationwide. Call early, especially for unfamiliar ingestions, pediatric exposures, or when the antidote/dosing below doesn't clearly fit the clinical picture. Supportive care (airway, breathing, circulation) always takes priority over antidote administration.

Toxin → Antidote — Quick Reference

Acetaminophen (APAP)

Hepatotoxicity

N-acetylcysteine (NAC)

IV: 150 mg/kg over 1h, then 50 mg/kg over 4h, then 100 mg/kg over 16h. PO: 140 mg/kg load, then 70 mg/kg q4h ×17. Treat per Rumack-Matthew nomogram — see below

Specific antidote

Benzodiazepines

CNS/respiratory depression

Flumazenil 0.2 mg IV

May repeat 0.3–0.5 mg q30–60s, max 3 mg. Avoid in chronic benzo users and mixed overdose with pro-convulsants (e.g. TCAs) — can precipitate seizures. Rarely indicated in undifferentiated overdose

Use with caution

Tricyclic antidepressants

Cardiotoxicity, QRS widening

Sodium bicarbonate 1–2 mEq/kg IV

Bolus for QRS >100ms or ventricular arrhythmia. Repeat to target serum pH 7.50–7.55. Continuous infusion for ongoing toxicity

Specific antidote

Beta-blockers

Bradycardia, cardiogenic shock

Glucagon 3–5 mg IV

Up to 10 mg bolus, then infusion 2–5 mg/hr. High-dose insulin/euglycemia therapy (HIET) for refractory shock — regular insulin 1 unit/kg bolus, then 0.5–1 unit/kg/hr with dextrose to maintain euglycemia

Specific antidote

Calcium channel blockers

Bradycardia, cardiogenic shock

Calcium gluconate 3g IV

(Or calcium chloride 1g), may repeat. HIET is now considered first-line for refractory shock (same regimen as beta-blockers). Lipid emulsion for severe refractory cases, especially lipophilic agents (verapamil)

Specific antidote

Digoxin

Life-threatening arrhythmia, hyperkalemia

Digoxin immune Fab (DigiFab)

Dose by ingested amount or serum level (product formula), or empiric 10–20 vials for life-threatening toxicity

Specific antidote

Methanol / Ethylene glycol

Toxic alcohol poisoning

Fomepizole 15 mg/kg IV load

Then 10 mg/kg q12h ×4 doses, then 15 mg/kg q12h if continued (enzyme induction). Hemodialysis for severe acidosis/renal failure/high level. Folate (methanol) or thiamine/pyridoxine (ethylene glycol) as cofactors

Specific antidote

Organophosphates / Carbamates

Cholinergic toxicity

Atropine 1–2 mg IV

Double dose q3–5min until secretions clear — may require massive cumulative doses. Add pralidoxime (2-PAM) 1–2g IV over 15–30min then infusion, most effective early; often unnecessary for carbamates alone

Specific antidote

Cyanide

Cellular hypoxia, lactic acidosis

Hydroxocobalamin (Cyanokit) 5g IV

Over 15 min, may repeat once. Alternative/adjunct: sodium thiosulfate 12.5g IV

Specific antidote

Iron

GI toxicity, shock, hepatotoxicity

Deferoxamine 15 mg/kg/hr IV

Continuous infusion for significant toxicity (elevated level, systemic symptoms, shock). Whole bowel irrigation if pills visible on imaging

Specific antidote

Isoniazid (INH)

Refractory seizures

Pyridoxine (B6) IV

Gram-for-gram matching ingested INH dose. Empiric 5g IV if amount unknown, for INH-induced seizures/status epilepticus

Specific antidote

Methemoglobinemia

Local anesthetics, dapsone, nitrates

Methylene blue 1–2 mg/kg IV

Over 5 min, may repeat in 1h if needed. Caution: can precipitate hemolysis in G6PD deficiency

Check G6PD if possible

Local anesthetic systemic toxicity

Cardiovascular collapse, seizures

Lipid emulsion 20%

Bolus 1.5 mL/kg IV over 1 min, then infusion 0.25 mL/kg/min. Repeat bolus for persistent cardiovascular collapse

Specific antidote

Sulfonylureas

Refractory hypoglycemia

Octreotide 50–100 mcg SC/IV

Q6–12h. Suppresses insulin release — prevents rebound hypoglycemia more effectively than dextrose alone

Specific antidote

Opioids

Respiratory depression

Naloxone

See the dedicated Naloxone Reference for full dosing by route, renarcotization risk, and ND-specific legal information

Specific antidote

Acetaminophen — Rumack-Matthew Nomogram Guidance

Single acute ingestion, known time

Draw APAP level at 4h post-ingestion (or later if ingestion time uncertain — never interpret a level drawn before 4h). Plot on Rumack-Matthew nomogram; treat with NAC if above the treatment line (150 mcg/mL at 4h).

Unknown ingestion time / staggered ingestion

Nomogram does not apply. Start NAC empirically if any suggestion of a potentially toxic ingestion (e.g. >7.5g or >150 mg/kg cumulative over <24h) while awaiting levels/LFTs — do not wait for a 4h level that will never be interpretable.

Delayed presentation / established hepatotoxicity

Start NAC regardless of level if there's evidence of hepatic injury (elevated AST/ALT) or presentation is >24h post-ingestion — NAC has benefit even in late/fulminant hepatic failure. Involve transplant hepatology early for severe cases.

General Principles

GI decontamination

Activated charcoal (1 g/kg) is most beneficial within 1–2h of ingestion for appropriate toxins — not all toxins bind charcoal (e.g. iron, lithium, alcohols). Whole bowel irrigation for iron, sustained-release products, or body packers. Gastric lavage is rarely indicated today.

Delayed presentations

Some ingestions look deceptively benign early — acetaminophen, sustained-release preparations, and some plant/mushroom toxins can have a symptom-free latent period before organ injury manifests. Don't be falsely reassured by an early asymptomatic exam.

Supportive care first

Airway, breathing, circulation take priority over antidote administration in every case. Many toxidromes are managed successfully with aggressive supportive care alone even when a specific antidote isn't available or isn't yet confirmed necessary.

When in doubt

Call Poison Control (1-800-222-1222) early — for unusual exposures, pediatric ingestions, unclear dosing, or antidote availability questions. Toxicology or critical care consultation for refractory or complex cases.

Resources

Poison Control — 1-800-222-1222 America's Poison Centers (AAPCC) American College of Medical Toxicology