Single Dose Pharmacokinetics of Kapanol™, a New Oral Sustained-Release Morphine Formulation

Abstract

Three single dose open-label crossover studies in healthy adult males (n = 24 or 30) evaluated the sustained release characteristics, bioavailability, influence of food, linearity of kinetics and metabolite to morphine molar ratios of Kapanol™ compared with oral morphine solution and MST Continus® tablets. Drugs were administered 7 days apart following either a 12-hour fast or a standard high-fat meal. All blood samples (36 or 48 hours) were analysed for morphine (high-performance liquid chromatography [HPLC]-electrochemical detection) and a subset was analysed for morphine-6-glucuronide (M-6-G) and morphine-3-glucuronide (M-3-G) [HPLC-ultraviolet]. Kapanol™ (fasted and fed) had a pharmacokinetic profile consistent with a sustained release of morphine (M) and there was no evidence of dose-dumping. No significant differences occurred in the dose-adjusted area under the plasma concentration-time curve (AUC) values for Kapanol™ (50mg) [fasted and fed] and solution (25mg) [fasted]. The bioavailability of Kapanol™ relative to solution was 107 and 111% on fasting and fed states, respectively. The AUC molar ratios of M-3-G and M-6-G to M were not significantly different for Kapanol™ and solution (mean molar ratio M: M-6-G: M-3-G =1:7: 30). Kapanol™ displayed linear pharmacokinetics over the dose range of 30 to 100mg. Kapanol™ 50mg had a slower absorption rate and a longer duration over which plasma morphine levels were equal to or above 75% peak concentration than MST Continus® 60mg, while no differences occurred in the extent of morphine absorption from the 2 formulations. In conclusion, the pharmacokinetics of Kapanol™ are consistent with a sustained-release formulation suitable for at least 12-hourly dose administration. The slow, sustained absorption of morphine from Kapanol™ may provide clinical advantages over other morphine preparations.