To evaluate the efficacy and safety of the investigational antinociceptive and anticonvulsant drug lacosamide dosed at 400mg/day in the treatment of diabetic neuropathic pain, data were collected from Phase II and III double-blind, randomized, placebo-controlled trials. Three fixed-dose trials (SP742, SP742, SP768) contained a 12-week maintenance period; the Phase II flexible-dose trial (SP614) consisted of a 4-week maintenance period. Primary outcome was within-subject change in average daily pain score (11-point pain scale) from baseline to the last 4 weeks of maintenance for the fixed-dose trials and from baseline to the end of maintenance for the flexible-dose trial.

Subjects receiving lacosamide 400 mg/day (n=426) showed numerically reduced pain scores over placebo (n=291) in all trials. Results were statistically significant in two trials (SP614; P=.04 SP742; P=.01) and at the level of significance in SP768 (P=.0507) for the primary variable. Significance was not reached in SP743, due to a strong placebo effect at the final visit. When using the secondary variable of change from baseline to the entire maintenance period, lacosamide 400mg/day significantly reduced pain over placebo in the fixed-dose trials (P=.02, P=.01 and P=.007 for SP742, SP743 and SP768, respectively). Treatment with 400 mg/day lacosamide resulted in the occurrence of four adverse events with an incidence >5% and greater than placebo: dizziness (13.8%), fatigue (7.7%), nausea (6.8%), and tremor (5.6%).

Lacosamide 400mg/day significantly reduced pain and showed good tolerability in clinical trials of diabetic neuropathic pain.