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Opioid Placebo Controlled Trials: The Need for
a Revised Methodology
M. Clark, R. Gironda
Posted: September 2005  
Journal of Pain, Vol. 6, March 2005

Opioid therapy is one of the most frequent interventions utilized in the treatment of individuals with chronic non-cancer pain. In the absence of long-term random-controlled trials (RCTs) of opioid effectiveness, double-blinded placebo RCTs examining the short-term effects of opioid therapy have been cited as evidence of opioid efficacy with this population. However, a comprehensive review of all identified opioid placebo RCTs revealed numerous methodological flaws that characterize this research (e.g., high termination rates; small sample sizes; contamination by the use of opioid rescue medications; brief RCT durations; lack of intent to treat analyses; incomplete methodologies; failure to report pain changes from baseline; use of nonstandard pain measures). Chief among these is evidence that the blinding integrity of almost every past placebo RCT was compromised. This presentation will review the empirical basis for this claim and identify the nature and extent of these failures in blinding procedures. Implications for past conclusions regarding the efficacy of opioids, when compared to placebos, will be presented. Suggestions for methodological improvements based on approaches utilized in social science methodologies designed to assess or compare the impact of sham interventions also will be discussed.