Bioequivalence study of two morphine extended release formulations after multiple dosing in healthy volunteers

Two extended release (ER) formulations of morphine sulphate (30 mg each), Oramorph SR (test) and a marketed reference formulation (MST Mundipharma Retardtabletten), were investigated for their relative bioavailability at steady-state:

The study was designed as a single-centre, open-label, two-period crossover, pharmacokinetic comparison in 28 healthy male volunteers and was completed in 23 subjects. The determination of morphine and its metabolite morphine-6-glucuronide in plasma was done by HPLC with electrochemical detection after solid-phase extraction.

Under steady-state conditions in the first dosing interval, mean maximum plasma concentrations for morphine were 19.1 ng/ml (CV% 41) for Oramorph SR 30 mg and 19.1 ng/ml (CV% 33) for MST-30 Mundipharma Retardtabletten. Geometric mean AUC(0-12) values were calculated as 108 ngxh/ml (CV% 40) for Oramorph SR 30 mg and as 118 ng x h/ml (CV% 30) for the reference formulation. The plasma concentrations of the major metabolite, morphine-6-glucuronide, were found to be generally in a higher range compared to the parent compound. The 90% confidence intervals of test to reference ratios calculated for all relevant parameters (AUC, C(max), PTF) for both the parent compound and morphine-6-glucuronide were all within the limits of 80 - 125%. The most frequent adverse events (AE > 10%) during Oramorph SR 30 mg treatment were headache (36%), dizziness (18%), nausea (21%), vomiting (21%) and pruritus (11%). During treatment with MST-30 Mundipharma Retardtabletten, the most frequent AEs were headache (29%), dizziness (13%), nausea (29%) and vomiting (29%).

The results demonstrate bioequivalence of Oramorph SR 30 mg and MST-30 Mundipharma Retardtabletten.