Characterization of palm olein-in-water emulsion as a vehicle for tropical drug delivery of betamethasone 17-valerate

Abstract

Palm olein, the major commodity of Malaysia, is inexhaustible and contains natural surfactants with the potential to be used widely in pharmaceutical formulations. However, there is little data available on the use of palm olein as an alternative in the production of topical products. The current study aims to produce pharmaceutical formulation using palm olein as the oil phase with betamethasone 17-valerate as the active ingredient and to compare the characteristics with those of commercial products. The emulsions were prepared using Span® 20 and Tween® 20 as surfactants, Carbopol® 940 as thickener, methyl paraben sodium, propyl paraben sodium and chlorocresol as preservatives, propylene glycol as solubilizer and distilled water as the aqueous phase. The formulations were characterised for particle size distribution, microscopic examination, viscosity, rheology, phase separation, pH and zeta potential. Evaluation on drug release with three different viscosities was further performed with Hanson Verticle Diffusion Cell System using cellulose acetate as well as rat skin as membranes and the samples were quantified with HPLC. The results were compared with that of three commmercially available products which were Betnovate, Betasone and Axcel Betamethasone creams. The creams stabilized with 0.3% (w/w) of Carbopol® 940 were further tested for microbial limit studies according to the monographs stated in the British Pharmacopoeia (2009). The creams were further subjected to stability studies for 3 months at three different temperatures (4?C, 25?C and 40?C) and degradation of betamethasone 17-valerate in the formulations was analysed using HPLC. The formulations showed mean particle size between 2 to 4 µm, viscosity 50 to 250 mPa.s, pH 5 to 5.9 and zeta potential -45 to -68 mV. The emulsions exhibited pseudoplastic behaviour with yield stress and found to be thixotrophic. The drug release rates from palm-olein-in-water emulsions were up to 4.5 times higher than that of commercial products. Less than 5 % of drug was degraded in the formulations during the 3-month period when they were subjected to three different temperatures. In conclusion, these findings proved that the creams produced from palm-olein-in-water emulsion could be a superior alternative vehicle for topical drug delivery system.