Examining the time-to-improvement of pain in patients with chronic neuropathic pain due to spinal cord injury

Chronic neuropathic pain due to spinal cord injury (SCI) is often severe and difficult to treat. Two randomized, placebo-controlled trials have demonstrated efficacy for pregabalin in the treatment of neuropathic pain due to SCI. These trials constitute the largest clinical database with respect to the pharmacologic treatment of SCI-related neuropathic pain. The current study examines the time-to- improvement in pain during these two trials. Daily pain scores were based on an 11-point numeric rating scale from 0 = no pain to 10 = worst possible pain. Changes in daily pain scores were analyzed using an analysis of covariance model in the intention-to-treat population (N= 343). The time-to-onset (TTO) for reduction in daily pain scores was calculated for both trials. TTO was defined as the first day pain scores for that particular day, and the following day, were significantly lower than placebo. Pregabalin treatment significantly reduced pain scores at endpoint compared to placebo in both trials. Mean placebo-adjusted improvements in pain scores at endpoint were -1.53 (LOCF; p < 0.001) and -0.78 (LOCF; p = 0.003) for the two trials. In one trial, the TTO for reduction in pain scores occurred on day one following initiation of treatment. Mean placebo-adjusted improvement in pain score on day one was -1.15 (p < 0.001) for this trial. In the remaining trial, the TTO for reduction in pain scores occurred on day two following initiation of treatment. Mean placebo-adjusted improvement in pain score on day two was -0.52 (p = 0.007) for this trial. These findings demonstrate that statistically significant and sustained pain relief occurs rapidly in response to pregabalin treatment in patients with neuropathic pain due to SCI. Funded by Pfizer Inc.