Acetaminophen Antidote
N-acetylcysteine (NAC) (restores glutathione stores; use Rumack-Matthew nomogram)
Methanol vs Ethylene Glycol
Methanol = Retinal toxicity / Snowstorm blindness; Ethylene glycol = Envelope calcium oxalate crystals / AKI
Toxic Alcohol Antidote
Fomepizole (competitive inhibitor of Alcohol Dehydrogenase)
Cyanide Antidote
Hydroxocobalamin (binds cyanide to form cyanocobalamin / Vitamin B12)
Master Clinical Poisoning & Specific Antidote Reference
The definitive antidote reference for medical licensing examinations:
| Toxin / Medication | Mechanism of Toxicity | Classic Clinical Presentation | First-Line Specific Antidote / Treatment |
|---|---|---|---|
| Acetaminophen (Tylenol) | NAPQI toxic metabolite depletes glutathione → centrilobular hepatic necrosis | Asymptomatic initially → RUQ pain, jaundice, encephalopathy at 48–72h | N-Acetylcysteine (NAC) (oral or IV) |
| Opioids (Heroin, Fentanyl) | μ-opioid receptor agonism in brainstem | Respiratory depression (< 8/min), pinpoint pupils (miosis), coma | Naloxone (Narcan) (titrate to adequate respiratory rate) |
| Benzodiazepines | GABA-A receptor allosteric positive modulation | CNS depression, normal vitals, ataxia, dysarthria | Flumazenil (CAUTION: can precipitate fatal seizures in chronic users) |
| Carbon Monoxide (CO) | Binds hemoglobin with 250x affinity of O2; shifts curve left | Headache, confusion, cherry-red skin (rare); pulse ox falsely normal | 100% High-Flow O2 via non-rebreather; Hyperbaric O2 if severe |
| Cyanide | Inhibits complex IV (Cytochrome c oxidase) of electron transport | House fire victim, almond breath, severe lactic acidosis despite high SvO2 | Hydroxocobalamin (first-line) or Sodium Thiosulfate / Nitrites |
| Ethylene Glycol (Antifreeze) | Oxidized by alcohol dehydrogenase to oxalic acid | Envelope-shaped calcium oxalate crystals in urine, AKI, HAGMA | Fomepizole (or ethanol) + emergent hemodialysis |
| Methanol (Windshield fluid) | Oxidized by alcohol dehydrogenase to formic acid | Visual blur / "snowstorm" blindness, optic disc hyperemia, HAGMA | Fomepizole + emergent hemodialysis |
| Salicylates (Aspirin) | Uncouples oxidative phosphorylation; stimulates respiratory center | Tinnitus, mixed respiratory alkalosis + anion gap metabolic acidosis | IV Sodium Bicarbonate (alkalinizes urine to ↑ excretion); hemodialysis |
| Tricyclic Antidepressants (TCAs) | Blocks fast cardiac Na+ channels (Phase 0) & alpha-1/histamine/muscarinic receptors | Wide QRS > 100 ms, tall terminal R wave in aVR, seizures, hypotension | IV Sodium Bicarbonate (increases extracellular Na+ and raises serum pH) |
| Beta-Blockers | Negative inotropy and chronotropy | Bradycardia, hypotension, hypoglycemia, cardiogenic shock | Glucagon (bypasses beta receptors to ↑ cAMP); High-dose insulin/glucose |
| Calcium Channel Blockers | Blocks L-type calcium channels | Bradycardia, hypotension, HYPERglycemia (inhibits insulin release) | IV Calcium Gluconate, High-Dose Insulin + Dextrose (HIE) |
| Digoxin | Inhibits Na+/K+ ATPase; increases vagal tone and intracellular Ca2+ | Yellow/green halos, nausea, vomiting, hyperkalemia, bidirectional VT | Digoxin-specific Fab fragments (DigiFab); treat hyperkalemia |
| Organophosphates / Nerve Agents | Irreversible inhibition of Acetylcholinesterase | SLUDGE symptoms, miosis, wheezing/bronchorrhea, muscle fasciculations | Atropine (until secretions dry) + Pralidoxime (2-PAM) |
| Heparin | Potentiates Antithrombin III | Bleeding, elevated aPTT | Protamine Sulfate (1 mg per 100 units heparin) |
| Warfarin | Inhibits Vitamin K Epoxide Reductase (VKORC1) | Bleeding, elevated INR | 4-Factor Prothrombin Complex Concentrate (4F-PCC) + IV Vitamin K |
| Lead Poisoning | Inhibits ferrochelatase and ALA dehydratase | Colicky abdominal pain, basophilic stippling, wrist/foot drop, lead lines | Dimercaprol (BAL) + CaNa2-EDTA (or oral Succimer/DMSA in children) |
COMLEX / OMM Integration
NBOME High-Yield Correlate
Autonomic Support in Toxic Ingestions
- Autonomic Somatic Reflexes: Acute toxic ingestions with intense GI cramping or hyperdynamic sympathetic responses produce profound somatic dysfunction along the thoracic chain (T1–T9).
- Rib Raising & Lymphatics: Soft tissue and rib raising help normalize sympathetic drive once the patient is medically stabilized and the specific antidote has been administered.
Board Traps & Common Distractors
- Trap: Giving Calcium for Digoxin toxicity. The old "stone heart" phenomenon was once feared; while calcium is generally avoided in digoxin-induced hyperkalemia, DigiFab is the undisputed treatment of choice.
- Trap: Administering Flumazenil routinely for unknown comas. Flumazenil in a patient with chronic benzodiazepine tolerance or co-ingested proconvulsants (such as TCAs) triggers intractable, fatal status epilepticus.