What can we learn from failed neuropathic pain trials?

Abstract

Neuropathic pain is a complication of nerve injury due to metabolic (diabetes), infectious (HIV, herpes zoster), or traumatic causes. While there has been progress with the introduction of pregabalin and duloxetine, a need still exists for additional therapies and targets. This need is offset by the growing cost and complexity of neuropathic pain trials.1 An improved understanding of factors that might improve trial design is critically important. In this issue of Neurology ®, Katz et al.2 take an important step in this direction. They describe factors that are associated with positive vs negative outcomes in placebo-controlled neuropathic pain trials and draw parallels to similar analyses of depression trials. They analyzed study characteristics of 105 clinical trials performed between 1966 and 2005 that were reported in a recent meta-analysis that focused on drug classes believed to have a treatment effect.3 In some instances, trials in neuropathic pain have failed to demonstrate a treatment effect though there were reasons to be optimistic for a positive result based on prior results. Examples include trials of lamotrigine and gabapentin in painful diabetic neuropathy.4 In multivariate regression analyses, Katz et al. reported that a greater medication …