Establishing the dosage equivalency of oxymorphone extended release and oxycodone controlled release in patients with cancer pain: a randomized controlled study

SUMMARY

Objective: To compare the analgesic efficacy and safety of oxymorphone extended release (ER) and oxycodone controlled release (CR) in patients with moderate to severe cancer pain.

Research design and methods: This randomized, multicenter, double-blind, 2-period crossover study included adult outpatients (≥ 18?years of age) with moderate or severe cancer pain who were first titrated for 3–10?days with open-label oxymorphone or oxycodone to achieve a stable dose that provided adequate analgesia with tolerable adverse events and no requirement for more than 2 doses of rescue medication per day. The subsequent double-blind treatment phase was a 7- to 10-day period of oxycodone CR or oxymorphone ER treatment followed by crossing over to the alternate medication for another 7–10?days. During the treatment phase, up to 2 doses per day of morphine sulfate 15-mg tablets were allowed as rescue.

Main outcomes and measures: Assessments included the Brief Pain Inventory, global evaluations, Karnofsky performance status, and clinical laboratory evaluations (serum chemistry profile, complete blood count, urinalysis). Efficacy variables were analyzed using a mixed-effects model with treatment, sequence, and period as fixed effects and subject as a random effect.

Results: Forty-seven patients entered the titration/stabilization phase, 44 received at least 1 dose of study drug, 42 completed the first double-blind phase, and 40 completed the second double-blind phase. Mean pain intensity scores and other efficacy parameters were comparable for the 2 groups. The mean daily dosage of oxycodone CR (91.9?mg) was twice that of oxymorphone ER (45.9?mg), an equianalgesic dose ratio of 2:1. Rescue medication use was low in both groups (approximately 1 tablet of morphine sulfate 15?mg/day). No significant differences in opioid adverse events were observed between the groups.

Conclusions: Adult patients with cancer who were taking oxycodone CR were readily converted to oxymorphone ER and required half the milligram dose to stabilize their pain. Within 72?h, most patients achieved a stable dose that provided adequate relief with similar opioid adverse events.