The relative bioavailability of morphine sulfate and naltrexone hydrochloride extended release capsules (EMBEDA®) and an extended release morphine sulfate capsule formulation (KADIAN®) in healthy adults under fasting conditions

Morphine sulfate and naltrexone hydrochloride extended release capsules (EMBEDA®, King Pharmaceuticals®, Inc., Bristol, TN), indicated for the management of chronic, moderate to severe pain, contain extended release morphine pellets with a sequestered naltrexone core (MS-sNT). If the product is tampered with by crushing, naltrexone, a μ-opioid antagonist, is intended for release to mitigate morphine-induced subjective effects. The primary end point of this randomized 2-way crossover study in healthy fasted volunteers was evaluation of morphine bioequivalence between MS-sNT (treatment A) and morphine sulfate extended release capsules (KADIAN®, treatment B). Morphine pharmacokinetics were assessed predose to 72 hours postdose of single 100-mg doses of treatment A or B. Analysis of variance of ln-transformed ratios of least squares mean of the area under the concentration time curve (AUC) from time 0 to last measurable concentration (AUC_0-t) and AUC from time 0 to infinity (AUC_inf) and maximum serum concentration (C _max) for treatments A versus B were performed. Ratios and 90% confidence intervals for least squares mean for AUC_0-t (102.2%; 98.6-105.9%), AUC_inf (97.4%; 91.2-104.1%), and C_max (93.8%; 82.4-106.7%) indicated bioequivalence between the 2 formulations. When subjects who vomited during the 12-hour dosing interval were excluded, the confidence interval for AUC_0-t and AUC_inf fell within the 80%-125% range, but the lower limit for Cmax was 76.9%.