Which is the Treatment of Choice for Acute Acetaminophen Overdose in a Situation Where a Serum Level Determination is Not Available Within 8 Hours: Oral or Intravenous N-Acetylcysteine Treatment?

ABSTRACT

PURPOSE: The purpose of this study was to develop therapeutic decision guidelines on N-acetylcysteine (NAC) treatment for acetaminophen (AAP) overdose in a situation where a serum level determination is not available within 8 hours. METHODS: We reviewed retrospectively the medical records of patients admitted for AAP overdose from January 2001 to February 2004. Forty-nine patients met inclusion criteria; patients with acute AAP overdose who were exposed to 7.5 g or 140 mg/kg or greater, determination of the serum level was not available within 8 hours, and NAC treatment was started empirically before identification of the serum level. The patients had been treated with a 72hour oral or a 20hour intravenous (IV) NAC treatment protocol. RESULTS: Patients were classified into an Oral NAC (n=24) group and an IV NAC (n=25) group based on the treatment protocol. There were no significant intergroup differences in patient characteristics, time variables, distribution of risk categories, and hepatotoxicity. All the patients in both toxic groups were fully recovered, and the difference in the number of adverse reactions during NAC treatment were not significant between the two groups (Oral NAC vs IV NAC, 4 (16%) vs. 2 (8%), respectively; p=0.417). The numbers of patients who discontinued the NAC treatment were 14 (58%) in the Oral NAC group and 8 (32%) in the IV NAC group (p=0.088). The six patients in the nontoxic category of IV NAC group were already completed before determination of the serum level. CONCLUSION: Therapeutic decisions for AAP overdose which are based entirely on ingestion history have some limitations. IV NAC is as effective as oral treatment for patients with acute AAP overdose. If the serum level is not available within 8 hours, the clinician should preventively administer the first dose of oral NAC to patients without severe vomiting. Subsequently, when the serum level is determined, the need for additional therapy should be determined to reduce unnecessary use of NAC. However, if the patients present with severe vomiting or contraindications to oral treatment, intravenous administration is required.