Patterns of acetaminophen toxicity among patients with low-risk serum concentrations.

Objective: In 2012, the Commission on Human Medicines mandated lowering the acetaminophen toxicity nomogram treatment threshold in the UK to 100 µg/ml at 4 h post-ingestion. The present study aim was to evaluate biochemical and liver toxicity patterns in patients who presented with acetaminophen overdose and had low serum acetaminophen concentrations (<150 µg/ml).

Methods: Patients admitted to the emergency department with a clear history of acute acetaminophen overdose with or without other medication or ethanol were consecutively enrolled into this retrospective cohort study. Patients with serum acetaminophen concentration >150 µg/ml or an unknown ingestion time were excluded. Data were extracted from electronic medical records and are presented as mean ± SD or median (interquartile range).

Results: A total of 103 patients were included (median age, 17 [4-21] years) and 80 (78%) were female. The median ingested acetaminophen dose was 5000 (2850-7650) mg. At baseline, the median serum acetaminophen concentration was 42 (4.5-64.8) µg/ml, and median alanine aminotransferase and aspartate aminotransferase levels were 22 (17-28) and 27 (16-45) IU/L, respectively. Twenty patients were treated with acetylcysteine, with none developing adverse reactions. No patient developed hepatotoxicity, including patients with initial multiple product ingestion or other risk factors.

Conclusions: Patients presenting with an acute acetaminophen overdose with acetaminophen level <150 µg/ml, including patients with other risk factors, are at low risk of hepatotoxicity.