Hot Melt Coating of Pellets for a Water Soluble Drug using Combination of Waxes

Abstract

Waxes retards drug release from dosage form based on their lipophilic characteristics. In this study, the effect of hot melt spray coated Verapamil pellets with composition of stearic acid, carnauba wax; glyceryl monostearate and polyethylene glycol on drug release and release kinetics were investigated. The verapamil pellets containing 70% microcrystalline cellulose (Avicel PH101) were prepared by extrusion-spheronization technique and spray coated with molten wax at various ratios and thickness in a hot-melt spray coating instrument. In-vitro drug release was studied using test method for Extended Release tablets USP 24. The drug release was decreased with increase in stearic acid concentration and addition of 5% carnauba wax to stearic acid minimized initial burst release but it also retarded drug release. Glyceryl monostearate 30%w/w as release modifier at 20%w/w coating level provided desired drug release while PEG 6000 provided similar results at 2.5%w/w concentration. The plot of log fraction drug unreleased versus time showed a good linear relationship. Glycerol monostearate at 30%w/w as release modifier showed higher release rate in initial hours which declined with time and also R2 value for first order release kinetics was found to be nearest to one indicating drug release was dependent on initial concentration present in pellets. A zero order release profile was obtained from verapamil HCl sustained release pellets prepared by hot melt spray coating of stearic acid with sitable combination of carnuba wax and PEG 6000.