Concomitant therapy in people with epilepsy: potential drug-drug interactions and patient awareness

People with epilepsy (PWE) may use prescription and over-the-counter (OTC) drugs for the treatment of concomitant diseases. Combinations of these drugs, as well as dietary supplements, with antiepileptic drugs (AEDs) may lead to reduced control of seizures and of coexisting medical conditions and increased risk of adverse drug reactions (ADRs). The aims of this study were to obtain comprehensive lists of medications, dietary supplements, botanicals, and specific food components used by adult PWE and to evaluate the potential for interactions involving AEDs and patients' awareness of such potential interactions. We conducted a prospective, questionnaire-based study of PWE attending the Hadassah-Hebrew University Epilepsy Clinic over a period of 7months. The questionnaire interview included the listing of medications, medicinal herbs, dietary supplements, and specific food components consumed and the knowledge of potential drug-drug interactions (DDIs), and it was conducted by a pharmacist. Drug-drug interactions were analyzed via the Micromedex online database. Out of 179 patients who attended the clinic over the study period, we interviewed 73 PWE, of which 71 were included in our final analysis. The mean number of AEDs consumed per subject was 1.7 (SD: 0.8, range: 1-4). Forty (56%) subjects were also treated with other prescription and/or OTC medications, and thirty-four (48%) took dietary supplements. Drug families most prone to DDIs involving AEDs included antipsychotic agents, selective serotonin reuptake inhibitors, and statins. Two-thirds of study participants (67%) knew that DDIs may lead to ADRs, but only half (56%) were aware of the potential for reduced seizure control. Only 44% always reported treatment with AEDs to medical professionals. This study provides for the first time a comprehensive picture of prescription and OTC drugs and food supplements used by PWE. Despite a considerable potential for DDIs involving AEDs, patient awareness is limited, highlighting the importance of patient and caregiver education.