Which is the treatment of choice for acetaminophen overdose when serum level determination is not available within eight hours? Comparisons on oral and intravenous N-Acetylcysteine treatment

Abstract

Study objectives: We develop a therapeutic decision guideline on N -acetylcysteine (NAC) for acetaminophen overdose when serum-level determination is not available within 8 hours. Methods: This was a retrospective medical record review on all eligible patients in 2 moderate-volume university hospitals in an urban setting. Forty-nine patients met inclusion criteria: patients with acute acetaminophen overdose who were exposed to 7.5 g or 140 mg/kg or greater, determination of serum level was not available within 8 hours, and NAC therapy was started empirically before identification of serum level. Interventions included patients being treated with 72-hour oral or 20-hour intravenous NAC treatment protocol. Results: Patients were classified into an oral-NAC (n=24) group and an intravenous-NAC (n=25) group according to treatment protocols. There were no significant intergroup differences on treatment groups for age, initial gastrointestinal decontamination, ingested amount, mean ingestion–admission interval, mean ingestion–NAC initiation, mean ingestion–identification of serum level, distribution of risk categories, or hepatotoxicity. Almost half the patients in each group were categorized as nontoxic (oral-NAC versus intravenous-NAC, 14 [58%] versus 14 [54%], respectively), and all patients in toxic groups recovered. Adverse reactions resulting from NAC treatment were also not significant between the 2 groups (oral-NAC versus intravenous-NAC, 4 [16%] versus 2 [8%], respectively; P =.417). The number of patients who discontinued the NAC treatment was 14 (58%) in the oral-NAC group and 8 (32%) in the intravenous-NAC group ( P =.088). However, the patients in the nontoxic category whose NAC treatment was completed before determination of serum level shown significant differences between the 2 groups (oral-NAC versus intravenous-NAC, 0% versus 43%, respectively; P =.016). Conclusion: Therapeutic decisions of acetaminophen overdose, which are based entirely on ingestion history, have some limitations. Intravenous therapy is as effective as oral therapy for patients with early acetaminophen overdose. If the hospital laboratory cannot determine the serum level 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 of additional therapy should be determined to reduce unnecessary use of NAC. However, if patients present with severe vomiting or contraindications to oral therapy, intravenous administration of NAC is required.