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

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Abstract
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. This randomized, multicenter, double-blind, 2-period crossover study included adult outpatients (>or= 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 and other efficacy parameters were comparable for 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. 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. 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 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. 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.