Role of repeated doses of oral activated charcoal in the treatment of acute intoxications.

While single dose activated charcoal is effective in preventing drug absorption, repeated doses not only prevent absorption but also can increase systemic drug clearance. The mechanism for the latter effect may involve interruption of enterohepatic recycling and/or promotion of drug exsorption from the systemic circulation into the gut lumen. A comprehensive review of reported studies in volunteer subjects and overdose patients showed that repeated dose activated charcoal markedly decreased the half-life and/or increased the clearance of a wide range of drugs. Side-effects of the treatment were infrequent, but included aspiration pneumonia, diarrhoea and constipation. The addition of laxatives to repeated dose charcoal treatment did not offer any significant increase in drug clearance and is not recommended. It is suggested that the optimal regimen for the use of repeat dose activated charcoal in acute drug intoxications is an initial dose of 75-100 g, followed by 50 g every 4 hours until the risks of systemic drug toxicity are reduced to an acceptable level.