Long-term retention rates of lamotrigine, gabapentin, and topiramate in chronic epilepsy

Purpose: We sought to determine the long-term retention rates of lamotrigine (LTG), gabapentin (GBP), and topiramate (TPM) therapy for patients at a tertiary referral clinic for chronic, refractory epilepsy. Methods: We analyzed 424 consecutive patients with chronic, refractory partial and/or generalized epilepsy who were started on LTG, 158 patients who were started on GBP, and 393 patients who were started on TPM. The percentages of patients who continued therapy with LTG, GBP, and TPM were estimated with the use of Kaplan-Meier survival analysis. Factors that influence retention were analyzed with the use of Cox regression analysis. Results: Kaplan-Meier survival analysis showed that at 3 years, 30% continued therapy on TPM compared with 29% on LTG and fewer than 10% on GBP. Adverse events resulted in therapy withdrawal in 40% of patients on TPM compared with GBP (37%) and LTG (22%). Perceived lack of efficacy led to treatment withdrawal in 39% of patients on GBP compared with 34% on LTG and 19% on TPM. Cox regression estimated that a fourth or fewer of patients with chronic partial epilepsy are likely to continue therapy with a new antiepileptic drug beyond 5 years. Conclusions: The impact of these new antiepileptic drugs on the long-term course of chronic partial epilepsy is likely to be small, as approximately three of four patients will discontinue therapy. More patients appear to continue on TPM compared with LTG or GBP, with a possible reason being better perceived efficacy of TPM, despite having the highest incidence of adverse events.