Predicting concentrations in children presenting with acetaminophen overdose

Objective: To predict serum concentrations to evaluate and improve guidelin es for the treatment of children (1 to 5 years) with accidental ingestion o f acetaminophen elixir. Methods: Acetaminophen concentrations for 1000 children were simulated with pharmacokinetic parameters and their expected variability. The distributio n of concentrations arising from a 300 mg/kg dose at different age groups w as predicted. These predictions were validated by comparison with concentra tions obtained at. 4 hours from 121 children with accidental ingestion of a cetaminophen elixir. Results: No child who presented with overdose had a concentration in the pr obable risk area of the Rumack-Matthew toxicity nomogram. Enteral charcoal administered 98 minutes (SD 44) after ingestion had no effect on serum conc entrations. The simulation predicted that an acetaminophen dose of 300 mg/k g would result in concentrations of 32 to 208 mg/L (95% CI) at 4 hours afte r ingestion. The maximum concentration occurred before 2 hours in 95% of si mulated children. Conclusion: Children (1 to 5 years) with reported ingestion of >250 mg/kg a cetaminophen elixir should have serum concentrations measured at 2 hours af ter ingestion rather than at the 4-hour time point recommended in adults. T his can be expected to speed discharge and reduce anxiety The use of entera l charcoal is unlikely to enhance acetaminophen elimination, unless it is g iven within an hour of acetaminophen ingestion.