Specific toxicology treatments and antidotes: activated charcoal
Specific toxicology treatments and antidotes: activated charcoal
Activated charcoal is manufactured by superheating distilled wood pulp, which creates a substance with a very large surface area that reversibly adsorbs many ingested toxins. It reduces the systemic absorption of drugs and poisons by binding the substance in the gastrointestinal tract and increasing clearance of some drugs/toxins by interruption of enterohepatic circulation or gastrointestinal dialysis, ie the drawing of already absorbed drugs/toxins back into the gastrointestinal tract down a concentration gradient, allowing subsequent excretion.
The effectiveness of charcoal in adsorbing a drug or toxin is dependent on:
- the drug/toxin's binding to charcoal
- the normal absorption properties of the drug/toxin
- any drug effect on gastrointestinal activity (eg ileus).
The effectiveness of charcoal in clearing a drug appears to depend on the normal clearance of the drug and enterohepatic recirculation of the drug.
Activated charcoal is generally administered in a sucrose-containing oral liquid. Formulation with the cathartic, sorbitol, provides no advantage. Tablets and capsules of activated charcoal are ineffective in acute poisonings.
Activated charcoal is unlikely to be effective for alcohols (including ethanol, ethylene glycol and methanol), strong acids and alkalis (corrosives) or metals (including gold, lithium, iron and potassium).
Activated charcoal should not be used where it is unlikely to provide measurable clinical benefit and/or where it is expected that good supportive care and antidote therapy alone would deliver a good outcome.
Activated charcoal can be taken orally by conscious and cooperative patients. Mixing it with ice-cream or other such food can improve palatability in children. It can be administered via an orogastric or nasogastric tube to conscious patients unable to take the dose orally, or to unconscious patients who have a protected airway.
Multiple-dose activated charcoal has been shown to increase clearance of some drugs. This effect is probably due to an extension of the effect of single-dose activated charcoal by extending the period charcoal is present in the gastrointestinal tract. This technique may have a role in severe overdoses of carbamazepine, phenobarbitone, dapsone, quinine and theophylline. Prior to each dose of activated charcoal the presence of bowel sounds must be confirmed.
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