Efficacy and safety of carisbamate in patients with diabetic neuropathy or postherpetic neuralgia: results from 3 randomized, double-blind placebo-controlled trials.

ABSTRACT

The results of 3 proof-of-concept studies to evaluate carisbamate's efficacy and safety in treating neuropathic pain are presented. In studies 1 (postherpetic neuralgia, n = 91) and 2 (diabetic neuropathy, n = 137), patients received carisbamate 400 mg/day or placebo for 4 weeks and then crossed over to the other treatment for 4 weeks. In study 3 (diabetic neuropathy, higher carisbamate doses), patients (n = 386) were randomized (1111) to receive either carisbamate 800 mg/day, 1200 mg/day, pregabalin 300 mg/day or placebo for 15 weeks. Primary efficacy end point was the mean of the last 7 average daily pain scores obtained on days the study drug was taken, for all 3 studies. Least square mean (95% CI) differences between carisbamate and placebo groups on the primary end point were as follows study 1 -0.512 (-1.32, 0.29) carisbamate 400 mg/day; study 2 -0.307 (-0.94, 0.33) carisbamate 400 mg/day; and study 3 -0.51 (-1.10, 0.08), carisbamate 800 mg/day; -0.55 (-1.13, 0.04), carisbamate 1200 mg/day; and -0.43 (-1.01, 0.15), pregabalin 300 mg/day. Neither carisbamate (all 3 studies) nor pregabalin (study 3) significantly differed from placebo, although multiple secondary end points showed significant improvement in efficacy with carisbamate in studies 1 and 2. Dizziness was the only treatment-emergent adverse event occurring at ≥10% difference in carisbamate groups versus placebo (study 1 12% vs. 1%; study 3 14% vs. 4%; study 2 1% vs. 2%). Carisbamate, although well tolerated, did not demonstrate efficacy in neuropathic pain across these studies, nor did the active comparator pregabalin (study 3).