The quality of evidence is downgraded by study limitations (unclear allocation concealment and lack of blinding), and by inconsistency (variability in results).
A Cochrane review [Abstract] 1 included 42 studies with a total of 4 485 subjects. The studies assessed the effectiveness and tolerability of oxycodone by any route of administration for pain in adults with cancer.
The ability of controlled-release (CR; typically taken every 12 hours) and immediate-release (IR; taken every 4-6 hours) oxycodone to provide pain relief were similar (SMD for pain intensity 0.12, 95% CI -0.1 to 0.34; 3 studies, n=319). Pooled analyses of adverse events showed no significant differences between CR and IR oxycodone for constipation, drowsiness/somnolence, nausea, and vomiting. There were no data available for quality of life or participant preference; 3 studies suggested that treatment acceptability may be similar between groups.
Pain intensity was lower (better) after treatment with CR morphine than CR oxycodone (SMD 0.14, 95% CI 0.01 to 0.27; 7 studies, n=882). This SMD is equivalent to a difference of 0.27 points on the Brief Pain Inventory scale (0-10 numerical rating scale), which is not clinically significant. There was little to no difference in the proportion of participants achieving complete or significant pain relief (RR 1.02, 95% CI 0.95 to 1.10; 13 studies, n=1 249). The RRs for constipation (RR 0.75, 95% CI 0.66 to 0.86; 18 studies, n=1 894) and for hallucinations (RR 0.52, 95% CI 0.28 to 0.97; 4 studies, n=696) were lower after treatment with CR oxycodone than after CR morphine. Pooled analyses of adverse events showed no significant differences between CR oxycodone and CR morphine for drowsiness/somnolence, nausea, and vomiting. No data were available for quality of life.
The remaining studies either compared oxycodone in various formulations or compared oxycodone to different alternative opioids. None found any clear superiority or inferiority of oxycodone for cancer pain, neither as an analgesic agent nor in terms of adverse event rates and treatment acceptability.
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