Does the patient history predict hepatotoxicity after acute paracetamol overdose?

Background: Initial management of patients who were presented to hospital after acute paracetamol overdose depends on the suspected amount ingested and more than 12 g is potentially fatal. However, the validity of this approach has received comparatively little attention. Methods: The present study is sought to establish whether the stated paracetamol dose might predict systemic exposure and risk of hepatotoxicity. A prospective observational study of consecutive patients presenting to the Emergency Department due to acute paracetamol overdose was performed. Serum paracetamol concentrations between 4 and 15 h post-ingestion were compared with the Rumack-Matthew ‘200-line’ nomogram, and hepatotoxicity was defined by prothrombin time ratio >1.3 or alanine transaminase ⩾1000 U/l. Results: There were 987 patients, and the stated quantity of paracetamol ingested was 0–12 g in 475 (48.1%), >12 g in 349 (35.4%) and unknown in 163 (16.5%). Ingestion of >12 g was associated with paracetamol concentration above the ‘200-line’ in 31.8% (95% CI 27.1–36.9%) vs. 3.2% (1.9–5.2%), P < 0.0001 by χ2 proportional test, and associated with hepatotoxicity in 6.9% (4.6–10.1%) vs. 1.3% (0.5–2.8%), P = 0.0001. Conclusions: Therefore, ingestion of >12 g predicted higher paracetamol exposure and increased risk of hepatotoxicity and supports the validity of patient history in this context.