Multicenter postmarketing surveillance of ondansetron therapy in pediatric patients

To identify prescribing patterns of ondansetron, to provide a general overview of the therapeutic responses and possible adverse effects to ondansetron in selected children's hospitals, and to evaluate this methodology of surveillance and assess its effectiveness as a means to collect postmarketing experience with a drug in pediatric patients.

This survey examined the use of ondansetron in 210 children. Complete drug and medical histories, indications, doses, possible ondansetron-associated adverse reactions, and daily responses to ondansetron therapy were recorded by a study pharmacist for each patient. Patients were followed until discharged from the clinic or hospital and/or until ondansetron therapy was discontinued.

The survey was conducted in seven free-standing children's hospitals across the US. Hospitals ranged in size from 100 to 331 beds (average 234). One hospital was located on the West coast, one on the East coast, one in the Rocky Mountain region, one in the Southwest region, and three in the Midwest.

The selection of study participants was limited to member free-standing children's hospitals of the Pediatric Pharmacy Administrative Group. Selection was based on geographic location and availability of a pharmacist to coordinate the study. One pharmacist at each study site served as surveillance coordinator. Each pharmacist monitored without intervention the use of ondansetron in 30 children. Patients were enrolled consecutively from physicians' orders for ondansetron. Enrollment was open to clinic and hospital patients. Patients were excluded if more than 48 hours of retrospective review was required.

The survey queried patient demographics, type of antineoplastic therapy administered, indications and dosing regimen(s) for ondansetron, additional antiemetic agents administered, and clinical response. Adverse drug reactions and prescriptions for ondansetron on discharge were recorded. An evaluation of response rates in hospital patients based on exposure to antineoplastic regimens causing acute (within 24 h) or delayed emesis (after 24 h) was formulated after data collection. Off-label use was summarized.

Surveys from 197 of the 210 patients enrolled were complete for evaluation. Ondansetron was used to treat chemotherapy-induced emesis in 88 percent of the patients and 12 percent received it for various other indications. Ondansetron dosing was off-label in 15 percent and 73 percent prior to and after an emetogenic exposure, respectively. Twenty-six percent of the patients were younger than four years. Dosages ranged from 0.15 to 0.45 mg/kg, given in various schedules. The injectable form was given both intravenously and orally. There was a significant difference in the mean number of doses in hospital (9 +/- 7.3) versus clinic (2 +/- 1.5) patients (p < 0.0001). Eighty-seven percent of all patients had a complete or major overall response. Possible ondansetron-associated adverse reactions were similar to those of previous reports for all patients, although some recorded reactions are not currently included in package labeling.

This study documents off-label use of ondansetron in children. Further study of ondansetron use in children less than four years of age, and for indications other than chemotherapy-induced emesis, is needed. Additional evaluation into the most cost-effective dosing of ondansetron would also be valuable.