Use of Ondansetron and Other Antiemetics in the Management of Toxic Acetaminophen Ingestions

Abstract

Background: Patients presenting with acetaminophen toxicity and vomiting are often treated with antiemetics so that orally administered N-acetylcysteine can be retained. The policy at the West Virginia Poison Center is to reserve ondansetron, an antiemetic with a higher cost than other antiemetics, as a second line agent for patients presenting within 8 hours of an acetaminophen ingestion. Methods: A retrospective study of cases between January 1993 and December 1995, in which the primary or secondary drug ingested was an adult-strength, acetaminophen-only formulation and the ingestion resulted in vomiting. Seventy-eight patients with laboratory-verified acetamin-ophen toxicity and vomiting were evaluated for the type of antiemetics used and the antiemetic's effectiveness. Results: Of the 78 acetaminophen toxic patients with vomiting, 17/51 patients (33.3%) who received a nonondansetron antiemetic failed therapy and required IV ondansetron. Of the 24 patients who received ondansetron, 4 patients (16.7%) failed therapy. All four patients who failed ondansetron therapy had previously failed other antiemetic therapy. Discussion: Although ondansetron had a lower failure rate than nonondansetron antiemetics, almost two-thirds of acetaminophen toxic patients with vomiting did not require ondansetron to control their vomiting. Health care costs would have been higher had these patients received ondansetron as their initial therapy. Antiemetics were found to be highly effective as only 3/78 patients (4%) required IV N-acetylcysteine secondary to antiemetic failure. Conclusions: Ondansetron should be utilized as a second-line agent in the management of acetaminophen toxic patients with vomiting. Because of its lower failure rate, ondansetron should be administered as a first-line agent in patients with a delay in N-acetylcysteine administration approaching 8 or more hours.