Methods to reduce toxin absorption

About Methods to Reduce Toxin Absorption

• Decontamination techniques are adjuncts in poisoning - not always indicated. ⚠️
• Effectiveness depends on time since ingestion, drug characteristics (lipid solubility, protein binding, enterohepatic recirculation), and patient safety (airway reflexes, consciousness).
• Most benefit seen if started within 1 hour of ingestion for immediate-release tablets; later use mainly for sustained-release, body packing, or enterohepatic drugs.

Gastric Lavage (“Stomach Pumping”) 🧴

• Now rarely indicated - only for massive, life-threatening ingestion within 1h when charcoal alone is insufficient (e.g. life-threatening TCA overdose).
• Safety: Must secure airway (intubation) - risk of aspiration is high. Patient in left lateral Trendelenburg position.
• Contraindications: Corrosives (acids/alkalis), hydrocarbons (petroleum) → aspiration → ARDS. ❌
• Method: Insert large-bore 36–40 Fr tube, instill 200–300 mL warm saline aliquots, aspirate repeatedly until clear. End with 50 g activated charcoal if safe.
• Exam pearl: Mentioned in finals, but in practice extremely rare due to complication risk.

Ipecac Syrup 🌿

• Historically used to induce vomiting. 🚫 Now obsolete in modern toxicology.
• Risks (aspiration, oesophageal tears, electrolyte imbalance) outweigh benefits.
• Exam trap: If offered as an option in MCQ/OSCE, the answer is almost always “No longer recommended”.

Activated Charcoal 🪨

• Mechanism: Porous carbon with surface area >500 m²/g; binds toxins by Van der Waals forces.
• Timing: Most effective within 1h, but may be used later for sustained-release or delayed gastric emptying drugs.
• Dose: Adults: 50–100 g (1 g/kg in children). Mix with water → slurry. Can be given via NG tube.
• Does NOT bind: Alcohols, glycols, metals (iron, lithium, sodium, potassium), strong acids/alkalis. ❌
• Adverse effects: Aspiration (esp. if drowsy/unprotected airway); constipation or bezoar formation with repeated doses.

Multi-Dose Activated Charcoal (MDAC) 🔄

• Use: Interrupts enterohepatic & enteroenteric circulation → speeds elimination.
• Dose: Initial 50–100 g, then 12.5–25 g every 2–4h (adults); children 10–25 g per dose.
• High-yield drugs: Theophylline, carbamazepine, quinine, phenobarbital, dapsone.
• Contraindication: Absent gag reflex/unprotected airway. ⚠️
• Exam tip: MDAC is often the answer in sustained-release or recirculating drug toxicity.

Total Bowel Irrigation (TBI) 🚽

• Method: Polyethylene glycol electrolyte solution (PEG) via NG tube at 1.5–2 L/hr (25–40 mL/kg/hr in children).
• Use: Until clear rectal effluent. Effective for:
  • Body packers (“drug mules” carrying cocaine/heroin in packets).
  • Sustained-release or enteric-coated drugs (iron, lithium, verapamil, theophylline, salicylates).
• Adverse effects: Aspiration if NG not placed correctly; discomfort; electrolyte shifts.

Dialysis & Extracorporeal Removal 💉

• Principle: Only effective if drug is:
  • Low molecular weight
  • Low protein binding
  • Small volume of distribution
  • Water-soluble
• Dialysable toxins (classic list):
  • Lithium
  • Alcohols (methanol, ethylene glycol, isopropanol)
  • Salicylates
  • Theophylline
  • Carbamazepine
  • Dabigatran, Valproate
  (Mnemonic: “LAST C D”)
• Methods: Haemodialysis (most effective), haemoperfusion (charcoal filters), haemofiltration in ICU if unstable.

Specific Overdose Complications 🚨

• Hyperthermia: Cooling measures; dantrolene if malignant hyperthermia/NMS suspected.
• Seizures: IV benzodiazepines (diazepam 5–10 mg, lorazepam 2–4 mg).
• Acute anxiety/agitation: Diazepam 2–10 mg IV.
• Bradycardia: Treat cause-specific → atropine, isoprenaline, pacing; calcium & insulin/glucose therapy for CCB overdose; glucagon for β-blocker overdose; digoxin-specific Fab fragments (Digibind) for digoxin poisoning.
• Nausea/vomiting: Antiemetics such as ondansetron or metoclopramide.

Clinical Pearls ✨

• 🚑 Always prioritise airway protection before any gastric intervention.
• ❌ Ipecac is outdated → don’t choose it in exams.
• 🪨 Activated charcoal = mainstay in most acute ingestions (if within 1h, airway safe).
• 🔄 MDAC = key for recirculating drugs (carbamazepine, theophylline, quinine, phenobarbital, dapsone).
• 🚽 TBI = “body packers” + sustained-release drugs.
• 💉 Dialysis = “LAST C D” toxins (Lithium, Alcohols, Salicylates, Theophylline, Carbamazepine, Dabigatran/Valproate).