Use of activated charcoal in a simulated poisoning with acetaminophen: A new loading dose for N-acetylcysteine?

Study objectives: To investigate the ability of a supranormal dose of N -acetylcysteine to overcome the effects of activated charcoal on N -acetylcysteine bioavailability and to determine the effects of activated charcoal on serum acetaminophen levels. Design, setting, and participants: Ten healthy adult volunteers participated in a controlled cross-over experiment. During phase I (control), subjects ingested 3 g acetaminophen, followed one hour later by the normal loading dose of N -acetylcysteine (140 mg/kg). During phase II (charcoal), subjects ingested 3 g acetaminophen, followed one hour later by 60 g activated charcoal and a supranormal loading dose of N -acetylcysteine (235 mg/kg). Main outcome measures: Serum levels of N -acetylcysteine were measured every 30 minutes for six hours. A serum acetaminophen level was measured at four hours. Results: The area under the curve for N -acetylcysteine was significantly higher for phase II than phase I ( P t -test). Peak N -acetylcysteine and time to peak were not significantly different. The four-hour serum acetaminophen level was significantly lower for phase II than phase I ( P t -test). Diarrhea occurred during both phases, but N -acetylcysteine was otherwise well tolerated. Conclusion: These results suggest that activated charcoal can be used safely for victims of acetaminophen overdose. A beneficial effect in preventing acetaminophen absorption can be expected if it is given within one hour after ingestion. If N -acetylcysteine is needed because of a toxic serum acetaminophen level, bioavailability can be ensured by increasing the N -acetylcysteine loading dose from 140 mg/kg to 235 mg/kg.