Safety profile of oxcarbazepine: results from a prescription-event monitoring study.

PURPOSE: To monitor safety of oxcarbazepine, prescribed in primary care in England, using prescription-event monitoring (PEM).

METHODS: Postmarketing surveillance using observational cohort technique of PEM. Exposure data were obtained from dispensed British National Health Service prescriptions issued by general practitioners (GPs) March 2000-July 2003. Demographic, drug utilization, and clinical event data were collected from questionnaires posted to GPs at least 6 months after first prescription date for each patient. Incidence densities (IDs) (number of first reports per 1,000 patient-months of treatment) were calculated and differences for events reported in month 1 (ID(1)) and months 2-6 (ID(2-6)) (99% confidence intervals) were examined for changes in event rates. Follow-up and causality assessment of medically significant events were undertaken.

RESULTS: The cohort comprised 2,243 patients [mean age 40.4 years; range 2-99 years; standard deviation (SD) 18.8; 46.3% (n = 1,038) male]. Most frequently reported primary indications were epilepsy, convulsion (n = 1,111; 49.5%, n = 209; 9.3%, respectively). GPs recorded 932 reasons for stopping medication in 698 (31.1%) patients; most frequent clinical reason "drowsiness/sedation" (n = 57; 2.5% of cohort). Clinical events (excluding indication) associated with starting treatment (lower 99% CI > 0) included: "drowsiness/sedation" (ID(1)-ID(2-6) = 14.2), "nausea/vomiting" (ID(1)-ID(2-6) = 13.0), and dizziness (ID(1)-ID(2-6) = 11.6). Events followed up and assessed as probably related to oxcarbazepine use included rash (7 of 11) and hyponatremia (15 of 38).

DISCUSSION: There were no serious adverse drug reactions reported during this study. Results of the study should be taken in context with other epidemiologic studies.