Measuring outcomes of treatment with antiepileptic drugs in clinical trials.

Epilepsy often requires life-long treatment with antiepileptic drugs (AEDs). For clinicians to meet the challenges of patient management, data on AED performance based on clearly defined and consistently applied outcome measures are needed. Ideally, the design of AED clinical trials should be relevant to real-world settings, providing reliable, valid, and comprehensive information on efficacy, tolerability, and quality of life (QOL). Several types of outcome parameters have been employed: percent seizure reduction, responder rate based on > or =50% seizure reduction, seizure-free rate, time to first seizure, time to Nth seizure, adverse events, QOL, retention, and compliance. Each provides important information about a drug's performance. Here we define and review endpoints for measuring AED treatment success and explore the concepts of efficacy, tolerability, QOL, retention, and compliance as well as their usefulness as clinical trial endpoints.