Meta-analysis of dropout rates in randomized controlled clinical trials: opioid analgesia for osteoarthritis pain.

BACKGROUND: The interpretation of opioid studies in patients with chronic pain due to osteoarthritis is limited by a high dropout rate. Therefore, the implication of dropouts on the recommendation of opioids in chronic osteoarthritis pain was analyzed. DATA SOURCES: The databases of Medline, Embase, the Cochrane Library, and the Internet from 1990-2009 were searched. STUDY SELECTION: Two independent authors included randomized controlled clinical trials investigating the effects of chronic opioid treatment for the management of osteoarthritis pain. In order to calculate the odds ratio, only placebo-controlled trials were included. DATA EXTRACTION: The primary outcome parameter was the dropout rate. Secondarily, the effect size was calculated. Data extraction was conducted by two independent authors. RESULTS: A total of 19 studies reporting results of 3,871 treatment and 2,080 placebo outcomes were retrieved. Compared to placebo, opioid treatment was associated with a significantly increased total dropout rate (OR = 1.3, 95%CI 1.2-1.4). Discontinuation of treatment was related to adverse events (OR = 4.0, 95%CI 3.4-4.6). Lack of analgesia was associated with a significantly reduced dropout rate in opioid groups (OR = 0.4, 95%CI 0.3-0.5). Analgesic effects were significantly better in opioid-treated patients (p = 0.01). CONCLUSION: In spite of analgesic effects, many osteoarthritis patients prefer to stop chronic opioid use, because of adverse events. Therefore, opioids are not generally recommended in osteoarthritis.