Safety and effectiveness of topiramate for the management of painful diabetic peripheral neuropathy in an open-label extension study

Abstract Objective: The aim of this study was to further assess the long-term safety and effectiveness of open-label topiramate therapy in subjects with moderately to severely painful diabetic peripheral neuropathy (DPN). Methods: Adults aged 18 to 75 years received open-label topiramate (25–600 mg/d for 26 weeks) in an extension of a previously published randomized, double-blind trial comparing topiramate with placebo. Safety analyses included adverse event (AE) reports and clinical laboratory tests. Metabolic end points included body weight and glycosylated hemoglobin (HbA 1c ). Effectiveness analyses included a 100-mm pain visual analog (PVA) scale, worst and current pain severity, and sleep disruption. Results: Two hundred five subjects participated in this open-label extension study (118 formerly treated with topiramate and 87 who formerly received placebo). The groups did not differ in baseline demographics or disease characteristics. One hundred twenty-four (60.5%) subjects (68.6% of former topiramate recipients and 49.4% of former placebo recipients) completed the extension study; the most common reason for discontinuation was an AE (27.3% of subjects). AEs among subjects who received ≥1 dose of topiramate (n = 298) included upper respiratory tract infection (16.1%), anorexia (15.1%), diarrhea (12.8%), nausea (12.8%), paresthesia (10.7%), and headache (10.1%). Baseline pain scores were lower in those formerly treated with topiramate (n = 117) than in the former placebo group (n = 86) (PVA: 43.3 vs 52.5, P = 0.014; worst pain: 1.9 vs 2.5, P P = 0.026; sleep disruption: 3.6 vs 4.6, P = 0.021). At the final visit, PVA, current pain, and sleep disruption scores were not significantly different between the former topiramate and former placebo groups, but worst pain differed significantly (1.4 vs 1.8; P = 0.025). Mean weight loss from the start of topiramate therapy was 5.2 and 5.3 kg in the former topiramate and former placebo groups, respectively ( P 1c values before and after topiramate treatment were 7.7% and 7.4%, respectively, in the former topiramate group ( P = 0.004 vs baseline), and 7.6% and 7.1%, respectively, in the former placebo group ( P Conclusion: Although 39.5% of subjects discontinued, most often due to AEs, the results of this 26-week, open-label extension study with topiramate (up to 600 mg/d) in subjects with moderately to severely painful DPN suggest that pain relief was effective and durable.