How long after drug ingestion is activated charcoal still effective?

The recent American Academy of Clinical Toxicology/European Association of Poisons Centres and Clinical Toxicologists position statement on activated charcoal stated "there are insufficient data to support or exclude its use after 1 hour of ingestion.'' The purpose of this study was to determine the effectiveness of activated charcoal administered 1, 2, and 3 hours after drug ingestion.

This was a human volunteer, randomized crossover study. Ten volunteers ingested 4 g of acetaminophen on four occasions at least 1 week apart. One ingestion served as a control and the other three as experimental ingestions with charcoal being administered at 1, 2, and 3 hours after acetaminophen dosing. Eight blood specimens were obtained over the initial 8 hours for serum acetaminophen concentrations that were used for calculation of routine pharmacokinetic parameters. Repeated measures of ANOVA and Tukey's HSD test were used for statistical analysis.

Pharmacokinetic parameters for acetaminophen in our volunteers were consistent with literature values. The mean area under the curve (AUC+/-SD) for the control and the 1-, 2-, and 3-hour groups were 221 +/- 54, 154 +/- 71, 206 +/- 67 and 204 +/- 58 mg/L/h, respectively. The 1-hour group was the only one differing from control (p < 0.01). The decrease of bioavailability at 1 hour was 30.3%, which is similar to previous studies.

Our data do not support the administration of activated charcoal as a gastrointestinal decontamination strategy beyond 1 hour after drug overdose.