Lacosamide is an anticonvulsant drug with the potential to reduce diabetic neuropathic pain. This trial assessed the long-term safety and efficacy of lacosamide in patients with painful diabetic neuropathy. Patients were titrated to their optimal lacosamide dose (up to 600 mg/day) in weekly increments of 100 mg/day prior to entering a long-term maintenance period with dose adjustments as necessary. Morning and evening pain, interference with sleep and activity were assessed by daily diary entries (11-point Likert scales). Scores for each visit were summarized as observed. Adverse events (AEs) were recorded throughout the trial.

Three hundred seventy-one patients (51% male, 49% female) were treated with lacosamide in the trial; 71% were <65 and 29% were ≥65 years of age. The most commonly prescribed lacosamide maintenance dose was 400 mg/day. The maximum duration of lacosamide exposure was 385 days. Clinically relevant reductions in pain scores were achieved during titration and were sustained over the entire treatment period. The mean (± SD) change of average daily pain score from baseline to the first 24 weeks of the maintenance phase across all dose groups was -3.81 (± 2.03). Nine percent discontinued the trial for AEs and 4% for lack of efficacy. The most common AEs were dizziness, vertigo, and headache.

In this long-term trial, lacosamide was generally well tolerated and led to early and sustained reductions in pain scores. These interim results indicate that patients may benefit from long-term treatment with lacosamide.