A Cochrane review [withdrawn from publication] included 4 studies with a total of 604 subjects (data for 504 participants were available for analysis). Two studies compared hydromorphone to oxycodone and 2 compared hydromorphone to morphine. Overall, there was no evident difference in treatment efficacy between groups, and participants achieved no worse than mild pain in all included studies. Hydromorphone versus oxycodone: One study reported VAS score (0 to 100 with higher score indicating worse outcome). The mean VAS endpoint pain intensity scores at 7 days were similar between groups (mean (± SD): hydromorphone 28.86 ± 17.08, n = 19; oxycodone 30.30 ± 25.33, n = 12). Another study reported Brief Pain Inventory (BPI) score (0 to 10 with higher score indicating worse outcome). The BPI change score of 'pain at its worst in the past 24 hours' from baseline was similar between groups at 28 days (hydromorphone -1.8 ± 3.29, n = 40; oxycodone -1.7 ± 3.91, n = 41). BPI score for 'mean pain in the past 24 hours' of the same study showed that both groups achieved no worse than mild pain (hydromorphone 2.9; oxycodone 3.3, SDs not reported, n = 81). Hydromorphone versus morphine: In one study, subscale data derived from the BPI scale showed that the morphine group appeared to have a higher endpoint mean score on 'worst pain' (mean ± SD: hydromorphone 3.5 ± 2.9, n = 99; morphine 4.3 ± 3.0, n = 101), nevertheless, mean scores on 'least pain' and 'mean pain' were almost identical.
There were several adverse events: some were the expected opioid adverse effects such as nausea, constipation and vomiting; others were not typical opioid adverse effects (for example, decreased appetite, dizziness and pyrexia), but generally showed no difference between groups. There were no data available for children or for several participant-important outcomes, including participant-reported pain relief and treatment impact on consciousness, appetite or thirst.
Comment: The quality of evidence is downgraded by imprecise results (few patients), and by suspected publication bias (only small and mostly commercially funded studies).