To determine the analgesic effectiveness, the effect on physical function and the safety of opioids in patients with osteoarthritis (OA).
A systematic literature search was performed in electronic databases up to October 2006. A hand search of references was also performed.
All randomized controlled trials evaluating the efficacy and/or the safety of opioids vs placebo or non-opioid analgesics in patients with OA were selected.
Data were collected using a predetermined form. Statistical analysis determined in each trial the effect size to assess the magnitude of treatment effect and the number needed to harm (NNH) to evaluate opioids safety.
Eighteen randomized placebo-controlled trials were analyzed, i.e., a total of 3244 participants who received opioids and 1612 who received placebo. The mean trial duration was 13+/-18 weeks. The pooled effect sizes of all opioids vs placebo for pain intensity and physical function were -0.79 (95% confidence interval, CI, -0.98 to -0.59) and -0.31 (95% CI -0.39 to -0.24), respectively. The NNH was calculated to be 5 vs placebo. The number of studies (n=4) that compared opioids with non-opioid analgesics (paracetamol and non-steroidal anti-inflammatory drugs) was too limited to provide robust data.
Opioids significantly decrease pain intensity and have small benefits on function compared with placebo in patients with OA. Adverse events, although reversible and not life threatening, often cause participants to stop taking the medication and could limit opioid usefulness. Moreover, the long-term efficacy and safety of these drugs for OA is yet to be determined due to the short mean trial duration.