Poison Decontamination Methods
On this page
Direct answer
Decontamination in the poisoned patient means removing unabsorbed poison from skin, eyes or gut — dermal washout with copious water, ocular irrigation, activated charcoal 1 g/kg for most ingestions within about an hour, gastric lavage only for life-threatening loads within an hour in a protected airway, and whole bowel irrigation with polyethylene glycol for sustained-release or non-charcoal-binding toxins like iron. Activated charcoal does not bind alcohols, lithium, iron, hydrocarbons, caustics or potassium salts, and syrup of ipecac has been abandoned. Decontamination is an adjunct to supportive care and specific antidotes, never a substitute, and each method has contraindications that exams love more than the methods themselves.
What you must remember
- Activated charcoal: 1 g/kg (50-100 g adult) as a slurry, ideally within 1 hour of ingestion; surface area adsorbs drugs onto itself; repeat doses (0.5 g/kg every 4-6 hours, about 4 doses) for theophylline, phenobarbitone, carbamazepine, digoxin, quinine — the "multipoint" toxins with enterohepatic or delayed absorption.
- Charcoal non-binders: lithium, iron, alcohols (ethanol, methanol, ethylene glycol), hydrocarbons, acids and alkalis, potassium — a one-mark list to memorise.
- Gastric lavage: orogastric tube 36-40 Fr adult, left lateral head-down, aliquots of 200-300 mL saline, only within about 1 hour and only for potentially lethal ingestions; contraindicated with corrosives, hydrocarbons (unless highly toxic), convulsing or comatose patients without a cuffed airway, and bleeding risk.
- Syrup of ipecac: obsolete — aspiration risk and no outcome benefit; say so in the viva.
- Whole bowel irrigation: polyethylene glycol-electrolyte solution 1.5-2 L/hour by nasogastric tube until clear effluent (about 4-6 hours), for sustained-release formulations, iron, body-packing of toxic illicit packages.
- Dermal and ocular: remove clothes (bagged), wash skin 10-15 minutes with soap and water — dry chemical powder brushed off first; irrigate eyes with normal saline or water for 15-30 minutes, pH check after alkali injury.
- Enhanced elimination beyond the gut: haemodialysis for methanol, ethylene glycol, lithium, salicylate, metformin, theophylline; multiple-dose charcoal and urinary alkalinisation for salicylate are exam staples.
- Indian practice anchor: poisoning cases route through emergency departments with toxicology support from centres such as the AIIMS poison control setup and the national toll-free poison information services; ABCs precede every decontamination decision.
An emergency sequence walked through
A 19-year-old arrives 40 minutes after swallowing "many" tablets of a sustained-release theophylline preparation, alert and vomiting. Airway, breathing, circulation and glucose come first; then decontamination is matched to the toxin. Charcoal 50 g goes down early because theophylline adsorbs superbly — and because its pharmacokinetics (distribution into a large volume, narrow therapeutic index, seizures and arrhythmias) make it worth the effort. The sustained-release formulation raises the stakes: whole bowel irrigation with polyethylene glycol at 2 L/hour is started once charcoal is in, running until rectal effluent clears, because kilogrammes of release-beads keep dissolving for hours. Contrast three patients in the next bays: a kerosene drinker gets no lavage (aspiration pneumonia is the killer, not absorption) and observation plus oxygen; a acid-ingestion patient gets nothing oral but analgesia, endoscopy planning and fluids — neutralisation is forbidden; and a iron-overdose toddler gets whole bowel irrigation plus desferrioxamine, since charcoal is useless against metals. The unifying logic: identify the toxin, weigh what is still in the gut against the risk of pushing decontamination, and remember that dialysis — not more charcoal — handles the already-absorbed load.
Where students slip
The examinable errors are predictable. One, ordering lavage at hour six or in an unprotected comatose patient — the evidence supports lavage only early and with airway control, and charcoal has largely displaced it. Two, charcoal for everything: the non-binder list (lithium, iron, alcohols, hydrocarbons, caustics) is precisely where questions hide. Three, neutralising acids with alkalis — the exothermic reaction adds thermal to chemical injury. Four, forgetting cathartics (sorbitol) are optional, single-dose, and avoided in children, ileus and renal failure with magnesium salts. Five, dialysis amnesia: a severely salicylate-toxic or methanol-poisoned patient needs the nephrology team early, because gut decontamination does nothing for absorbed drug.
Frequently asked questions
What is the dose and timing of activated charcoal?
1 g/kg as a slurry, preferably within 1 hour of ingestion; repeat doses help drugs with delayed or enterohepatic circulation such as theophylline and phenobarbitone.
Which poisons does activated charcoal not adsorb?
Lithium, iron, alcohols (ethanol, methanol, ethylene glycol), hydrocarbons, caustics and potassium — memorise this list.
When is gastric lavage still justified?
Within about an hour of a potentially life-threatening ingestion, in a cooperative or well-protected-airway patient, where charcoal alone seems insufficient.
What is whole bowel irrigation and when is it used?
Nasogastric polyethylene glycol solution at 1.5-2 L/hour until clear effluent, used for sustained-release drugs, iron, and body-packers.
Which poisons warrant haemodialysis?
Methanol, ethylene glycol, lithium, severe salicylate poisoning, metformin lactic acidosis and theophylline overdose with severe features.