Patterns of antiepileptic drug use in patients with potential refractory epilepsy in Texas Medicaid

Antiepileptic drug (AED) monotherapy is usually effective in 60% of the patients with epilepsy while the remaining patients have refractory epilepsy. This study compared treatment patterns (adherence, persistence, addition, and switching) associated with refractory and nonrefractory epilepsy.

Texas Medicaid claims from 09/01/07-12/31/13 were analyzed, and patients eligible for the study 1) were between 18 and 62 years of age, 2) had a prescription claim for an AED during the identification period (03/01/08-12/31/11) with no prior baseline AED use (6-month), and 3) had evidence of epilepsy diagnosis within 6 months of AED use. Based on AED use in the identification period, patients were categorized into "refractory" (≥3AEDs) and "nonrefractory" (<3AEDs) cohorts. The index date was the date of the first AED claim. Patients in both cohorts were matched 1:1 using propensity scoring and compared for adherence (proportion of days covered (PDC) ≥80% vs. <80%), persistence, addition (yes/no), and switching (yes/no) using multivariate conditional regression models. Conditional logistic regression and Cox proportional hazard models were used to address the study objectives.

Of the 10,599 eligible patients, 2798 (26.5%) patients in the refractory cohort were matched to patients in the nonrefractory cohort. Patients in the refractory cohort had significantly higher (p < 0.005) mean (±Standard deviation (SD)) adherence (88.6% (±19.1%) vs. 77.0% ± (25.8%)) and persistence (328.0 (±87.3) days vs. 294.9 ± (113.4) days) as compared with patients in the nonrefractory cohort. Compared with patients with nonrefractory epilepsy, patients with refractory epilepsy were 3.6 times (odds ratio (OR) = 3.553; 95% confidence interval (CI) = 3.060-4.125; p < 0.0001) more likely to adhere to AEDs and had a 34.7% (hazard ratio (HR) = 0.653; 95% CI = 0.608-0.702; p < 0.0001) lower hazard rate of discontinuation of AEDs. Also, patients with refractory epilepsy were 3.7 times (OR = 3.723; 95% CI = 2.902-4.776; p < 0.0001) more likely to add an alternative AED and 3.6 times (OR = 3.591; 95% CI = 3.010-4.284; p < 0.0001) more likely to switch to an alternative AED.

Patients with refractory epilepsy were significantly more likely to adhere and persist to AED regimen and were significantly more likely to add and switch to an alternative AED than patients with nonrefractory epilepsy.