Drug Toxicity and Overdose

General Management of Poisoning - The First Response

• Initial Stabilization (ABCDs):
  • Airway: Secure.
  • Breathing: Oxygen, ventilate if needed.
  • Circulation: IV access, fluids, vasopressors.
  • Disability: GCS, pupils, glucose (check & correct).
• Decontamination: Goal: Prevent absorption.
  • Skin/Eyes: Remove clothes, irrigate.
  • GI Decontamination:
    • Activated Charcoal (AC): 1 g/kg. Best within 1 hr. 📌 Not for PHAILS (Petroleum, Heavy metals, Alcohols, Iron, Lithium, Solvents/Corrosives).
    • Gastric Lavage: Rarely used; within 1 hr for severe cases.
    • Whole Bowel Irrigation (WBI): Body packers, SR tabs, metals.
• Enhanced Elimination:
  • Multiple Dose AC (MDAC): For enterohepatic recirculation (Theophylline, Phenobarbital, Carbamazepine, Dapsone).
  • Urinary Alkalinization: Salicylates, Phenobarbital.
  • Hemodialysis: Severe cases (Salicylates, Lithium, Ethylene glycol, Methanol, Barbiturates). 📌 I STUMBLE.

⭐ Prioritize ABCDs stabilization before decontamination or antidotes in all poisoning cases.

Paracetamol & Opioids - Popular Poisons

Paracetamol (Acetaminophen) Toxicity

• Mechanism: Glutathione depletion → NAPQI (toxic metabolite) accumulation → hepatic necrosis.
• Toxic dose: >150 mg/kg or >7.5 g. Peak hepatotoxicity: 72-96h.
• Diagnosis: Rumack-Matthew nomogram (use ≥4h post-ingestion).
• Antidote: N-acetylcysteine (NAC).
  • IV regimen: 150 mg/kg (1h), then 50 mg/kg (4h), then 100 mg/kg (16h).
  • Best if given within 8-10h.

  ⭐ NAC is also used for contrast-induced nephropathy prevention.

Opioid Overdose

• Classic triad: Coma, respiratory depression, miosis (pinpoint pupils).
  • ⚠️ Mydriasis: meperidine, hypoxia.
• Antidote: Naloxone.
  • Dose: 0.4-2 mg IV/IM/SC; repeat. Max initial: 10 mg.
  • Continuous IV infusion for long-acting opioids (e.g., methadone) due to naloxone's short half-life (30-90 min).

OPs & Heavy Metals - Chemical Chaos

• Organophosphates (OPs): Irreversible AChE inhibitors.
  • 📌 DUMBELS/SLUDGE (muscarinic); Muscle weakness, paralysis (nicotinic).
  • Rx: Atropine (2-5 mg IV, titrate), Pralidoxime (PAM, 1-2 g IV for nicotinic signs, <48h).
• Heavy Metals: Chelation therapy is key.
  • Lead (Pb): Paint, batteries. Colic, anemia, wrist drop. Chelation: BAL+EDTA (severe), Succimer (DMSA).
  • Arsenic (As): Garlic breath, rice-water stools. Chelation: BAL, DMSA.
  • Mercury (Hg): Neurotoxicity (organic), renal (inorganic). Chelation: DMSA, BAL (not methylHg).
  • Iron (Fe): GI bleed, acidosis, liver damage. Rx: Deferoxamine IV (if severe, serum Fe >500 µg/dL). ⭐ > Deferoxamine causes "vin rosé" urine.
• Toxic Alcohols (Methanol, Ethylene Glycol): ↑AGMA, ↑Osmolal gap.
  • Methanol → Formic acid (blindness). Ethylene Glycol → Oxalic acid (renal failure).
  • Rx: Fomepizole (15 mg/kg LD) or Ethanol; Hemodialysis. Folate (Methanol), Thiamine/Pyridoxine (EG).

Toxidrome Spotting - The Poison Profiler

Recognizing toxidromes is key when the specific poison is unknown.

High‑Yield Points - ⚡ Biggest Takeaways

• Key antidotes: N-acetylcysteine (paracetamol), naloxone (opioids), flumazenil (benzodiazepines), atropine/pralidoxime (organophosphates).
• Identify toxidromes (e.g., cholinergic, anticholinergic) for rapid diagnosis.
• Management: ABCDE, decontamination (activated charcoal), enhanced elimination.
• Paracetamol toxicity: Hepatotoxicity risk; use N-acetylcysteine per Rumack-Matthew nomogram.
• Organophosphates: Treat with atropine (muscarinic) and pralidoxime (cholinesterase regeneration).
• Salicylate poisoning: Mixed acid-base disturbance; alkaline diuresis is key.
• TCA overdose: Sodium bicarbonate for QRS prolongation (cardiotoxicity).