Pharmacokinetics and dose-proportionality of oxymorphone extended release and its metabolites: Results of a randomized crossover study

Study Objective. To evaluate the pharmacokinetics and dose-proportionality of four dose strengths (5, 10, 20, and 40 mg) of oxymorphone extended release (ER) under both single-dose and steady-state conditions. Design. Randomized, three-period, four-sequence, crossover study. Setting. Bioavailability clinic. Subjects. Twenty-four healthy adult volunteers. Intervention. Each subject received three of the four possible doses. The three 8-day administration periods were separated by a 7-day washout. Plasma was collected for up to 48 hours after a single dose on day 1 and during a 12-hour dosage interval at steady state. Naltrexone was administered to reduce opioid-related adverse effects. Measurements and Main Results. Twenty-three subjects completed at least one study period. Dose-proportionality and linearity were confirmed after single doses (mean oxymorphone ER area under the concentration versus time curve [AUC] 4.54, 8.94, 17.80, and 37.90 ng(.)hr/ml for 5-, 10-, 20-, and 40-mg doses, respectively) and at steady state (mean oxymorphone ER AUC 5.60, 9.77, 19.3, and 37.0 ng(.)hr/ml for 5-, 10-, 20-, and 40-mg doses every 12 hrs, respectively). Similar results were found for maximum plasma concentration. Metabolite (6-hydroxyoxymorphone and oxymorphone-3-glucuronide) plasma levels also increased in a linear fashion after single-dose administration and at steady state. Conclusion. The pharmacokinetic profile of oxymorphone ER demonstrates linearity and dose-proportionality under single-dose and steady-state conditions for the parent compound and its metabolites for doses of 5-40 mg.