OBJECTIVE: To evaluate the patient characteristics, diagnosis/comorbidities, and real-world dosing among Medicaid patients prescribed topiramate. METHODS: A retrospective database analysis was conducted using South Carolina (SC) and Texas (TX) ambulatory Medicaid claims from October 1, 2003 through December 31, 2004. Patients were required to have ≥2 topiramate prescriptions during the study period and were required to be < 65 years old. Patients were categorized into four cohorts: 1) epilepsy only; 2) migraine only; 3) epilepsy and migraine; and 4) neither epilepsy nor migraine. A comprehensive set of additional diagnoses, based on literature search, Micromedex compendium, and USPDI, was also examined. Demographic characteristics and average daily dose of topiramate (ADDoT) were summarized using descriptive statistics. RESULTS: During 2004, there were 2216 patients in SC Medicaid and 4766 patients in TX Medicaid meeting the study selection criteria. Mean (SD) age was 29.9 (15.9) in SC, and 27.1 (16.1) in TX. In SC, the cohort classification percentages were 32.3% (epilepsy only), 29.7% (migraine only), 10.7% (epilepsy and migraine), and 27.3% (neither epilepsy nor migraine). In TX, the cohorts were 39.6% (epilepsy only), 16.4% (migraine only), 9.2% (epilepsy and migraine), and 34.9% (neither epilepsy nor migraine). In the neither epilepsy nor migraine cohort, the most common diagnoses were bipolar disorder and depression. Mean (SD) ADDoT in the epilepsy only cohort was 205.2 mg (157.5) [SC], 239.6 mg (182.1) [TX]. The ADDoT in the migraine only cohort was 136.5 mg (112.6) [SC], 150.0 mg (129.6) [TX]. CONCLUSION: This is the first study to examine patterns of topiramate use in two Medicaid populations. It revealed that topiramate was prescribed in a young population, and approximately 70% of patients had an epilepsy and/or migraine diagnosis.