Acetaminophen protein adducts (APAP adducts) were quantified in 157 adolescents and children presenting at eight pediatric hospitals with the chief complaint of APAP overdose. Two of the patients required liver transplantation, whereas all the others recovered spontaneously. Peak APAP adducts correlated with peak hepatic transaminase values, time-to-treatment with N-acetylcysteine (NAC), and risk determination per the Rumack-Matthews nomogram. A population pharmacokinetic analysis (NONMEM) was performed with post hoc empiric Bayesian estimates determined for the elimination rate constants (k(e)), elimination half-lives (t(1/2)), and maximum concentration of adducts (C(max)) of the subjects. The mean (+/-SD)k(e) and half-life were 0.486 +/- 0.084 days(-1) and 1.47+/- 0.30 days, respectively, and the C(max) was 1.2 (+/-2.92) nmol/ml serum. The model-derived, predicted adduct value at 48 h (Adduct 48) correlated with adductC(max), adduct T(max), Rumack-Matthews risk determination, peak aspartate aminotransferase (AST), and peak alanine aminotransferase (ALT). The pharmacokinetics and clinical correlates of APAP adducts in pediatric and adolescent patients with APAP overdose support the need for a further examination of the role of APAP adducts as clinically relevant and specific biomarkers of APAP toxicity.