N-acetylcysteine for Acetaminophen Poisoning Without Hepatotoxicity: the Effect on the Prothrombin Time

Lee, Won Jae; Park, Kyu Nam; Choi, Seung Pil; Lee, Mi Jin; Wee, Jung Hee; So, Byung Hak

Abstract

PURPOSE
In patients with acetaminophen poisoning, clinical severities are partly based on the prothrombin time. In several conditions, N-acetylcysteine (NAC) infusion has been shown to lower the prothrombin index. Thus, we studied the effect of NAC on the prothrombin time in patients intoxicated with acetaminophen without hepatotoxicity.
METHODS
From March 2000 to Aug 2004, we reviewed the medical records of 149 patients with a diagnosis of acetaminophen poisoning. After 88 patients had been excluded (29 had hepatocellular injury, 14 had a probable risk based on their normogram, and 45 had a missing prothrombin index value), 61 patients were included in the analysis. The prothrombin time was recorded before and serially during NAC treatment.
RESULTS
The mean baseline prothrombin time was 99.1%, 99.3% after intravenous NAC infusion, and 74.0% at 8 hrs after initiation of NAC infusion. It decreased rapidly at 16 hrs, and reached a steady baseline state between 16 to 24 hrs. A rapid increase in the baseline time occurred after 2-3 days when the NAC infusion was stopped. After oral NAC treatment, it decreased rapidly from 8 to 16 hrs, and reached a steady baseline after 2 days. There was a rapid increase after 3~4 days when the NAC infusion was stopped.
CONCLUSION
In patients with uncomplicated acetaminophen poisoning, the decrease in the prothrombin index might be misinterpreted as a sign of liver failure, leading to a prolonged treatment.