Background. The research and clinical studies demonstrated the analgesic efficiency of topical application of morphine preparations. This study was aimed to determine the most suitable composition in model preparations of morphine hydrochloride and morphine sulphate for their transdermal bioavailability and to assess the effects of various promoters on the rate of exchange at the phase junction.
Material and methods. Eight different eucerin and five Carbopol based model ointment and hydrogel vehiculum formulations, respectively, in addition to the promoters of transdermal diffusion including glycerin, oxyethylenated lanoline, monoethanolamine, diethanolamine and triethanolamine were studied. The formulations were used for the preparation of ointment and hydrogel containing the same standardized amount of morphine in the chemical form of hydrochloride and sulphate. Furthermore, the following properties of morphine preparations were tested: the rate of evaporation of volatile ingredients at the phase junction, viscous elasticity, viscosity, pH, the diffusion rate of morphine hydrochloride and morphine sulphate.
Results. Hydrogels differ by the velocity of releasing violatile components (especially water). Water solution of MCl and MS added to hydrogels increase their viscous elasticity. Carbopol 980 F-based hydrogels characterize higher viscous elasticity.
Conclusions. Morphine sulphate and hydrochloride formulations differ with respect to viscous elasticity and viscosity of model ointments. The viscous elasticity is higher and viscosity lower in case of morphine sulphate formulations. Viscous elasticity of model hydrogels is related with the type of Carbopol, the highest value was found in case of Carbopol 980 NF. The viscous elasticity and viscosity of tested ointment formulations was not altered by the promoters used in the study. The rate of evaporation of volatile ingredients form studied hydrogel formulations depends on the type and concentration of Carbopol. Glycerin increases the rate of evaporation. Morphine sulphate diffuses more readily than morphine hydrochloride in vitro from the surface of model hydrogels through tomophane into the water. The rate of direct diffusion from the surface of ointment into the water is higher in case of morphine sulphate formulations. The most efficient promoters of transdermal diffusion of morphine hydrochloride and morphine sulphate are diethylamine and combined oxyethylenated lanoline and triethanolamine, respectively.