The efficacy of activated charcoal in the treatment of poisoning was first described in the 1700s, although it was Tovery’s survival after ingesting a strychnine and charcoal slurry before the French Academy of Medicine in 1831 that dramatized its life-saving effects (1,2).

Activated charcoal is created from the exposure of carbon-containing materials (usually low-ash wood) to steam and acids, producing a finely granular substance with a surface area of approximately 1,000 m²/g.

The microscopic pores of activated charcoal permit adsorption of drugs and other large-molecular-weight substances. Activated charcoal, in fact, effectively adsorbs almost all toxins, with notable exceptions including alcohol, metals and minerals, hydrocarbons, and cyanide. Maximal adsorption of toxins by charcoal occurs when the charcoal-drug ratio is 10:1.

Because of its effectiveness both in preventing systemic absorption of an ingested toxin (i.e., enhancement of preabsorptive elimination) and in accelerating the elimination of already absorbed toxins (i.e., postabsorptive elimination enhancement), charcoal has become the most important intervention in the treatment of toxic exposures. Because gastric emptying and cathartic administration provide only modest benefit after toxic ingestion, increasing data support the administration of activated charcoal alone (3,4).

Activated charcoal is indicated in two distinct circumstances. First, it should be considered after the ingestion of any toxin known to be adsorbed by activated charcoal. Second, it may be valuable in enhancing the elimination of drugs that can be removed by gastrointestinal dialysis (e.g., theophylline, phenobarbital, salicylates) or drugs that are known to have substantial elimination of parent compound and/or pharmacologically active metabolite through the bile (e.g., carbamazepine). In the case of theophylline and phenobarbital, oral charcoal will enhance the elimination of drug that has been administered intravenously (5,6).

The window of opportunity for clinical effectiveness depends on the absorption characteristics of the toxin. With toxins in which gut absorption is complete within 2 to 4 hours, activated charcoal has a clear role only if it is administered in that time frame. In contrast, for drugs with delayed gut absorption (e.g., drugs with anticholinergic activity), activated charcoal is potentially effective in preventing drug absorption for up to 12 hours postingestion. Current recommendations suggest that activated charcoal’s benefit is maximal if given within 1 hour of ingestion.

Contraindications to activated charcoal are loss of airway control, ingestion of a caustic agent (because such victims should be NPO and because endoscopic evaluation cannot be easily performed after charcoal administration), and gastrointestinal obstruction or perforation.