Context: The risk of hepatotoxicity secondary to acute acetaminophen overdose is related to serum acetaminophen concentration and lag time from ingestion to N-acetylcysteine (NAC) therapy. Psi (Greek letter ψ) is a toxicokinetic parameter that takes the acetaminophen level at 4 h post-ingestion ([APAP](4 h)) and the time-to-initiation of NAC (tNAC) into account and was found to be significantly predictive of hepatotoxicity in Canadian patients with acetaminophen overdose treated with intravenous NAC.
Objective: We report the relationship of psi and hepatotoxicity in a Thai population with acute acetaminophen overdose.
Methods: This is a retrospective study of patients with acute paracetamol overdose during January 2004 to June 2009 at Siriraj Hospital. Patients were treated with the standard 21-h intravenous NAC regimen. Univariate analyses were performed with logistic regression to assess the relationships of psi, [APAP](4 h), and tNAC, and hepatotoxicity.
Results: A total of 127 patients were enrolled. The median (interquartile range; IQR) of [APAP](4 h) was 267.8 (196.0-380.0) mg/L. The median (IQR) of tNAC was 8.5 (6.2-12.0) h. Thirteen patients (10.2%) developed hepatotoxicity. Univariate analysis revealed [APAP](4 h), tNAC, and psi as statistically significant predictors of hepatotoxicity.
Discussion and conclusion: The psi parameter is a reliable prognostic tool to predict hepatotoxicity secondary to acute acetaminophen overdose treated with intravenous NAC. Our evidence shows that psi may be a more superior tool than either acetaminophen level or time-to-initiation of NAC at predicting hepatotoxicity.