Improvement in pain severity category in clinical trials of pregabalin

BACKGROUND Pregabalin is approved by the US Food and Drug Administration for the treatment of fibromyalgia (FM), diabetic peripheral neuropathy (DPN), postherpetic neuralgia (PHN), and neuropathic pain due to spinal cord injury (SCI). Approval was based on clinical trial data demonstrating statistically significant differences in pain scores versus placebo. However, statistically significant pain relief may not always equate to clinically meaningful pain relief. To further characterize the clinical benefit of pregabalin, this analysis examined shifts in pain severity categories in patients with FM, DPN/PHN (pooled in this analysis), and SCI treated with pregabalin. METHODS Data were pooled from 23 placebo-controlled trials in patients with FM (1,623 treated with pregabalin, 937 placebo), DPN/PHN (2,867 pregabalin, 1,532 placebo), or SCI (181 pregabalin, 175 placebo). Pain scores were assessed on an 11-point numeric rating scale and categorized as mild (0 to <4), moderate (4 to <7), or severe (7 to 10). Only patients with mean score ≥4 at baseline were randomized to treatment. The percentage of patients shifting pain category from baseline to endpoint for pregabalin and placebo was analyzed using a modified ridit transformation with the Cochran-Mantel-Haenszel procedure. RESULTS A higher proportion of patients shifted to a less severe pain category at endpoint with pregabalin compared with placebo. With flexible-dose pregabalin, the percentage of patients improving from: severe to mild (pregabalin versus placebo) was 15.8 versus 13.4 in FM patients, 36.0 versus 16.6 in DPN/PHN patients, 14.3 versus 7.7 in SCI patients; severe to moderate was 28.7 versus 28.2 in FM patients, 32.5 versus 28.2 in DPN/PHN patients, 35.7 versus 28.2 in SCI patients; and moderate to mild was 38.3 versus 26.4 in FM patients, 59.5 versus 41.4 in DPN/PHN patients, 38.6 versus 27.2 in SCI patients. CONCLUSION Compared with placebo, pregabalin is more often associated with clinically meaningful improvements in pain category in patients with FM, DPN, PHN, or SCI.