☠️ Chapter 129: Rare and Dangerous Poisons

Beta-blockers (glucagon) · Calcium channel blockers (calcium, insulin-euglycaemia) · Digoxin (Fab antibodies) · Sulphonylureas (octreotide) · Metformin (lactic acidosis, dialysis) · TCA (sodium bicarbonate) · INH (pyridoxine) · Cyanide (hydroxocobalamin) · SSRI (serotonin syndrome)

🔍 Core Concepts: Rare & Dangerous Poisons

💊 Beta-Blockers
Bradycardia, hypotension, hypoglycaemia. Antidote: glucagon 0.1 mg/kg IV (bolus then infusion). Atropine, pacing, high-dose insulin euglycaemia (HIET) for refractory shock.
💊 Calcium Channel Blockers (CCB)
Bradycardia, hypotension, hyperglycaemia. Antidote: calcium gluconate 0.3-0.5 mL/kg IV. HIET (insulin 1-10 U/kg/h + dextrose) for refractory shock. Glucagon.
💊 Digoxin
Arrhythmias (brady/tachy), hyperkalaemia, nausea. Antidote: Digoxin-Fab antibodies. Avoid calcium (risk asystole).
💊 Sulphonylureas (Oral hypoglycaemics)
Severe hypoglycaemia. Antidote: octreotide (1 μg/kg IV/SC q6h) + dextrose. Dismisses insulin release.
💊 Metformin
Lactic acidosis, hypotension. No specific antidote. Supportive care, sodium bicarbonate, haemodialysis.
🧠 TCA (Tricyclic Antidepressants)
Wide QRS, seizures, hypotension. Antidote: sodium bicarbonate 1-2 mEq/kg. Avoid class Ia/IC antiarrhythmics.
🧬 INH (Isoniazid)
Refractory seizures, metabolic acidosis. Antidote: pyridoxine (1 g per 1 g INH, max 5 g). Benzodiazepines.
💀 Cyanide
Severe metabolic acidosis, coma, hypotension. Antidote: hydroxocobalamin 70 mg/kg IV (or sodium thiosulfate + amyl nitrite).

🩺 Stepwise Approach: Rare & Dangerous Poisons

1
Beta-blocker/CCB overdose → bradycardia, hypotension
IV fluids, atropine. Glucagon (0.1 mg/kg IV) for beta-blockers. Calcium gluconate (0.3-0.5 mL/kg) for CCB. HIET (insulin 1-10 U/kg/h + dextrose) for refractory shock. Pacing if needed.
2
Digoxin toxicity → arrhythmias, hyperkalaemia
Digoxin-Fab antibodies. Correct hyperkalaemia (insulin+glucose, calcium avoided — risk asystole). Treat bradycardia with atropine/pacing.
3
Sulphonylurea overdose → hypoglycaemia
IV dextrose. Octreotide 1 μg/kg IV/SC q6h (suppresses insulin release). Monitor glucose for 24-48h.
4
TCA overdose → wide QRS, seizures
Sodium bicarbonate 1-2 mEq/kg IV (narrows QRS). Benzodiazepines for seizures. Avoid phenytoin, procainamide, lidocaine.
5
INH overdose → refractory seizures, metabolic acidosis
Pyridoxine (vitamin B6) 1 g per 1 g INH (max 5 g) IV. Benzodiazepines. Sodium bicarbonate for acidosis.
6
Cyanide poisoning → severe lactic acidosis, coma
Hydroxocobalamin 70 mg/kg IV (or sodium thiosulfate + amyl nitrite). Supportive care, 100% oxygen.