Topiramate prescribing patterns among medicaid patients: diagnosis, comorbidities, and dosing.

Background: Routine clinical practice data are useful for payers and formulary decision makers to make sound decisions regarding coverage policy. Based on a literature search, there has been scant research into topiramate prescribing patterns among Medicaid patients.

Objective: The aim of this study was to describe diagnoses, demographic characteristics, additional co-existing diagnoses, and dosing among Medicaid patients prescribed topiramate.

Methods: This descriptive, retrospective database analysis used data from South Carolina (SC) and Texas (TX) ambulatory Medicaid claims dated October 1, 2003, to December 31, 2004. Patients whose data were eligible for inclusion in the study were enrolled in Medicaid during the study period, had >or=2 topiramate prescriptions, were aged <65 years, and had evidence of a topiramate treatment-related diagnosis (possible diagnoses were identified through literature search and drug compendiums). Four cohorts were defined: (1) epilepsy only; (2) migraine only; (3) epilepsy and migraine; and (4) nonepilepsy/nonmigraine. Demographic characteristics, diagnoses, comorbidities, and daily dose of topiramate were summarized using descriptive statistics. The initial study analysis (period 1) was a 180-day window comprising the 90 days before and after the first available topiramate prescription claim was filed. A second, 360-day analysis (period 2) was completed comprising the 180 days before and after the index topiramate prescription date.

Results: In the 180-day analysis, 2216 SC and 4766 TX Medicaid patients met the selection criteria. Cohort classification percentages were 32.3% and 39.6% (epilepsy only), 29.7% and 16.4% (migraine only), 10.7% and 9.2% (epilepsy and migraine), and 27.3% and 34.9% (nonepilepsy/nonmigraine) for SC and TX, respectively. Mean (SD) ages were 29.9 (15.9) (SC) and 27.1 (16.1) (TX) years. In the nonepilepsy/nonmigraine cohort, the most common diagnoses were bipolar disorder and depression. The median daily doses in the epilepsy-only cohort were 175 mg/d in the SC group and 200 mg/d in the TX group. In the migraine-only cohort, the median daily dose was 100 mg/d in SC and TX. Results for the 360-day analysis were similar.

Conclusions: In this descriptive study using data from 2 Medicaid populations, the majority of patients using topiramate had a diagnosis of epilepsy and/or migraine. Median dosages ranged from 175 to 200 mg/d in patients with epilepsy and 100 mg/d in those with migraine. Depression was a common comorbidity in the migraine cohort and the nonepilepsy/nonmigraine cohort.