Factors associated with poor seizure control and increased side effects after switching to generic antiepileptic drugs.

Objective: To determine those factors associated with increased seizures and side effects after switching from brand name to generic antiepileptic drugs (AEDs).

Methods: We surveyed adult epilepsy patients and obtained demographic, clinical, and psychosocial data. We inquired whether they switched from brand name to generic AEDs, and whether they experienced poorer seizure control and increased side effects. Using univariate analysis, we determined those variables significantly associated with increased seizures and side effects. We applied binary logistic regression to determine those independently associated with these target variables.

Results: One hundred and twenty-one subjects completed the questionnaire. Seventy-one switched to generic AEDs. Of these, 18 subjects (25.7%) reported increased seizure frequency. This was associated with high seizure count (p=0.03) and scores on the Beliefs About Medicines-General (BMQ-G) questionnaire (p=0.04). On multivariate analysis, these variables were not independently significant. Fourteen subjects (20.6%) reported increased side effects. This was associated with being African-American (p=0.04), and high scores on the BMQ-G (p=0.01). On multivariate analysis, BMQ-G scores were independently associated with increased adverse effects.

Interpretation: High baseline seizure count is associated with increased seizure frequency while high BMQ-G scores are associated with increased seizure frequency and adverse effects when patients switch from brand name to generic AEDs.