Six RCTs met the inclusion criteria for the review (n=1,489 participants randomised, of which 1,426 patients completed at least one pain assessment and were included in intention-to-treat analyses; 831 patients completed the trials). Three trials received a high quality score, and three trials a medium quality score. Sample size estimations were reported in five trials. Methods for randomisation and allocation concealment were reported in four trials. External validity was rated high in the one trial of malignant pain, medium in three trials and low in two trials.
Oxymorphone in chronic non-malignant pain (five RCTs; n=1,384 patients analysed): The analgesic effect of 20mg of oxymorphone did not differ from placebo (one trial). Pain intensity was significantly reduced for oxycodone compared to placebo groups for doses of: 40mg (-12.41, 95% CI -21.42 to -3.39; two RCTs) with considerable heterogeneity; doses of 80mg (-15.27, 95% CI -21.59 to -8.95; four trials) with considerable heterogeneity; and doses of 100mg (-12.20, 95% CI -20.90 to -3.50; one RCT). Most of the adverse events were those commonly observed with opioid treatment, with constipation occurring at the highest rate. The authors stated that the drop-out rates due to adverse events were high in trials of non-malignant pain (rates were above 30% in three trials).
Oxymorphone in malignant pain (one RCT; n=42 randomised patients): In this crossover trial, pain was well controlled and indistinguishable for oxymorphone and oxycodone. Adverse events were mild to moderate and related to the opioids.