• Aaron Vinik, Birol Emir, Raymond Cheung, and Ed Whalen.
• Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, VA, USA. VinikAI@evms.edu
• Clin Ther. 2013 May 1;35(5):612-23.

BackgroundIn patients with chronic pain due to diabetic peripheral neuropathy (DPN) or postherpetic neuralgia (PHN), pregabalin treatment results in pain relief and improved patient function/quality of life (QoL). Few studies, however, have examined the exact relationship between pain relief and improvements in patient function/QoL. It is unclear, for example, whether pregabalin has a direct independent effect on patient function/QoL or whether improvements in function/QoL are an indirect consequent of pain relief.ObjectivesTo determine whether improvements in function/QoL in response to pregabalin treatment are related to the extent of pain relief in patients with neuropathic pain due to DPN or PHN and to determine whether pregabalin has a direct independent effect on patient function/QoL that is distinct from its effects on pain.MethodsData from 11 randomized, double-blind, placebo-controlled trials of pregabalin for the treatment of DPN or PHN were pooled for this analysis. Changes in patient function/QoL scores were plotted according to the extent of pain relief to assess whether greater levels of pain relief were associated with greater improvement in function/QoL. A novel mediation analysis was used to asses to what extent the effects of pregabalin on function/QoL scores are a direct treatment effect as opposed to an indirect effect mediated through improvements in pain or sleep.ResultsModerate-to-substantial pain relief (a ≥30% decrease in pain) in response to pregabalin treatment was associated with significant (P < 0.05) improvements in 36-Item Short Form Health Survey (SF-36) scores (used to assess patient function/QoL). In many patients, greatest improvement in SF-36 scores was reported by patients achieving ≥50% decrease in pain. Analysis of Patient Global Impression of Change scores revealed a similar trend, where >80% of patients who achieved substantial pain relief also reported their status as much or very much improved. A substantial direct pregabalin treatment effect was evident for many SF-36 domains that could not be explained by pain relief or improvement in sleep.ConclusionsIn patients with chronic pain due to DPN or PHN, improvements in patient function/QoL in response to pregabalin treatment are correlated with the extent of pain relief. However, such improvements in function/QoL are not mediated entirely through pain relief but are the result of a combination of pregabalin's effects on pain and sleep disturbance and a direct effect on patient function itself.Copyright © 2013 Elsevier HS Journals, Inc. All rights reserved.

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