• Irma H Benedek, Janet Jobes, Qinfang Xiang, and William D Fiske.
• Endo Pharmaceuticals Inc, Chadds Ford, PA 19317, USA.
• Drug Des Dev Ther. 2011 Jan 1;5:455-63.

BackgroundA formulation of crush-resistant extended-release opioids may deter abuse. The purpose of this study was to evaluate the bioequivalence of oxymorphone extended-release (Oxy-ER) and a crush-resistant formulation of oxymorphone extended-release (Oxy-CRF).MethodsIn three open-label, randomized studies, healthy adults at a clinical research center received two single oral doses of Oxy-ER and two single doses of Oxy-CRF, each separated by a ≥7-day washout. Doses were administered under fasted conditions (study 1, 5 mg doses; study 2, 40 mg doses) or after a high-fat breakfast (study 3, 40 mg doses). Subjects administered 40 mg doses also received naltrexone. The primary endpoint was systemic oxymorphone exposure; the bioequivalence criterion was met if the 90% confidence intervals of the geometric mean ratio (Oxy-CRF/Oxy-ER) for oxymorphone area under the curve from time 0 to the last measured concentration (AUC(0-t)), AUC from time 0 to infinity (AUC(0-inf)), and maximum plasma concentration (C(max)) were within 0.8-1.25. Safety was assessed by monitoring adverse events.ResultsIn studies 1, 2, and 3, the safety population comprised 30, 37, and 36 subjects and the pharmacokinetics population comprised 27, 30, and 29 subjects, respectively. Oxy-ER and Oxy-CRF produced similar mean ± standard deviation oxymorphone AUC(0-t) (study 1, 5.05 ± 1.55 versus 5.29 ± 1.52 ng · h/mL; study 2, 31.51 ± 10.95 versus 31.23 ± 10.33 ng · h/mL; study 3, 50.16 ± 14.91 versus 49.01 ± 14.03 ng · h/mL) and C(max) (0.38 ± 0.11 versus 0.37 ± 0.12 ng/mL; 2.37 ± 1.20 versus 2.41 ± 0.94 ng/mL; 5.87 ± 1.99 versus 5.63 ± 2.26 ng/mL) under all conditions. The 90% confidence intervals for plasma oxymorphone AUC(0-t), AUC(0-inf), and C(max) fulfilled the bioequivalence criterion. Adverse event rates were similar with Oxy-ER and Oxy-CRF (study 1, 25% versus 23%; study 2, 9% versus 16%; study 3, 20% each group).ConclusionOxy-CRF and Oxy-ER (5 mg and 40 mg) are bioequivalent under fasted and fed conditions, suggesting that Oxy-CRF will have clinical efficacy and safety equivalent to Oxy-ER.

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