Preparation and evaluation of microcapsules containing propranolol hydrochloride using Eudragit polymers

Microencapsulation is a well-known method used to modify drug release. In this study, propranolol hydrochloride and Eudragit RS or RL microcapsules were prepared in order to assess the suitability of them as oral sustained release dosage form. Microcapsules were prepared using emulsion solvent evaporation method.The effect of formulation variables (polymer: drug ratio, polymer type, inclusion of triethyl citrate) and increase in stirring rate were investigated on microcapsule characteristics (shape, percentage yield, drug entrapment efficiency,mean particle size and drug release). All microcapsules were spherical with smooth surface. Percentage yield and drug entrapment efficiency were more than 90% for most formulations. The mean particle size for most of microcapsules was about 800 μm. Increase in stirring rate reduced the mean particle size but it did not affect the release properties. The release rate of drug decreased with increase in polymer:drug ratio for both polymers however the release rate was faster for Eudragit RL microcapsules. Addition of triethylcitrate to Eudragit RS microcapsules did not have any considerable effect on the release rate of drug. Propranolol hydrochloride and Eudragit RS or RL microcapsules were successfully prepared by emulsion solvent evaporation method. Increase in polymer:drug ratio decreased the release rate of drug but due to high water solubility of propranolol HCl the release rate was nearly rapid even at 4:1 Eudragit RS:drug and therefore further reduction in release rate is still required to achieve sustained release of propranolol hydrochloride.