Antidotes

Pharmacology Basics

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Antidotes counteract specific drug toxicities. Memorize these high-yield drug → antidote pairs — they show up on exams and in real emergencies.

Drug → Antidote Pairs

Acetaminophen (Tylenol)N-acetylcysteine (NAC, Mucomyst)

Most effective within 8 hours of overdose

Opioids (morphine, fentanyl, heroin)Naloxone (Narcan)

Short half-life — repeat dosing often needed

Benzodiazepines (diazepam, midazolam)Flumazenil (Romazicon)

Avoid in chronic users — seizure risk

HeparinProtamine sulfate

1 mg neutralizes ~100 units heparin

Warfarin (Coumadin)Vitamin K (phytonadione)

FFP or PCC for severe bleeding (faster reversal)

DigoxinDigoxin immune Fab (Digibind)

For severe toxicity, hyperkalemia, life-threatening arrhythmias

IronDeferoxamine

Chelates iron; urine turns reddish (vin rosé)

LeadSuccimer (oral) / EDTA (IV)

Chelation therapy

Beta-blockers / Calcium channel blockersGlucagon

Bypasses beta receptor; reverses bradycardia & hypotension

Organophosphates (insecticides)Atropine + Pralidoxime (2-PAM)

SLUDGE symptoms: salivation, lacrimation, urination, defecation, GI upset, emesis

Magnesium sulfateCalcium gluconate

Reverses respiratory depression and loss of DTRs

CyanideHydroxocobalamin or sodium thiosulfate

Often inhalation injury (smoke from fires)

Methanol / Ethylene glycolFomepizole (or ethanol)

Blocks alcohol dehydrogenase

MethotrexateLeucovorin (folinic acid)

'Leucovorin rescue' after high-dose MTX

tPA / thrombolyticsAminocaproic acid

Antifibrinolytic — stops bleeding

Anticholinergics (atropine, TCAs)Physostigmine

'Hot, dry, red, mad, blind' — reverses anticholinergic toxidrome

Cholinergic crisis / myasthenia overdoseAtropine

Reverses muscarinic effects (SLUDGE)

Have It Ready

Always have naloxone available when administering opioids
Always have protamine available when running heparin drips
Always have calcium gluconate at bedside during magnesium infusions (preeclampsia)
Reversal may be SHORTER than the toxic drug — repeat dosing or infusion may be needed

Key Pearls

Document antidote, dose, time, and patient response
Anticipate withdrawal after reversing opioids or benzodiazepines
Activated charcoal is NOT an antidote — it's GI decontamination (within 1 hour, awake patient)
Call Poison Control: 1-800-222-1222 (US)

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Disclaimer: PharmPal Nurse is for education only and is not medical advice. Do not use it to diagnose, treat, prescribe, or make patient-care decisions; always verify with current drug references, your instructor, facility policy, and a licensed provider. In emergencies, call local emergency services.