How long after drug ingestion is activated charcoal still effective?

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