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Understanding specific toxicities and their antidotes is crucial for medical students preparing for USMLE Step 1. Below is an organized guide with toxins, their respective treatments, and key points to remember.
Toxin | Treatment | Mechanism/Note |
---|---|---|
Acetaminophen | N-acetylcysteine | Replenishes glutathione. |
AChE inhibitors, organophosphates | Atropine > pralidoxime | Atropine blocks muscarinic effects; pralidoxime restores enzyme. |
Antimuscarinic, anticholinergic agents | Physostigmine (crosses BBB), control hyperthermia | Physostigmine reverses CNS toxicity. |
Arsenic | Dimercaprol, succimer | Chelates arsenic. |
Benzodiazepines | Flumazenil | Competitive GABA receptor antagonist. |
β-blockers | Atropine, glucagon, saline | Glucagon increases cAMP in cardiac cells. |
Carbon monoxide | 100% O2, hyperbaric O2 | Displaces CO from hemoglobin. |
Copper | Penicillamine, trientine | Chelates copper. Mnemonic: “Penny”cillamine. |
Cyanide | Hydroxocobalamin, nitrites + sodium thiosulfate | Converts cyanide to excretable forms. |
Digitalis (digoxin) | Digoxin-specific antibody fragments | Binds and neutralizes digoxin. |
Heparin | Protamine sulfate | Neutralizes heparin’s negative charge. |
Iron (Fe) | Deferoxamine, deferasirox, deferiprone | Chelates iron. |
Lead | Calcium disodium EDTA, dimercaprol, succimer, penicillamine | Chelates lead. |
Mercury | Dimercaprol, succimer | Chelates mercury. |
Methanol, ethylene glycol (antifreeze) | Fomepizole > ethanol, dialysis | Inhibits alcohol dehydrogenase. |
Methemoglobin | Methylene blue, vitamin C | Converts methemoglobin to hemoglobin. |
Opioids | Naloxone | Opioid receptor antagonist. |
Salicylates | Sodium bicarbonate (NaHCO₃), dialysis | Alkalinizes urine, enhances excretion. |
TCAs | Sodium bicarbonate (NaHCO₃) | Stabilizes cardiac cell membrane. |
Warfarin | Vitamin K (delayed effect), PCC/FFP | Replenishes clotting factors. |