Development and evaluation of sustained-release propranolol wax microspheres.

To obtain a sustained-release dosage form with a lack of gastric unwanted effects, wax microspheres containing propranolol (I) were prepared by a congealable dispersion microencapsulation technique. The effects of the process variables; type of wax, speed of emulsification, amount of drug loaded, type and amount of emulsifier, were studied on the entrapment efficiency, angle of repose, dissolution efficiency (DE), in-vitro drug release and mean particle size of (I) microspheres, by a factorial design. The results showed that changes in the amount of emulsifier (Tween), 0.04% and 0.08%, the type of Tween (80 and 20) and the wax type; beeswax or ceresine, caused a significant decrease in the entrapment efficiency. All the variables had an effect on the angle of repose and particle size of the (I) microspheres. The only significant parameter affecting the DE was the nature of the wax. The drug release in pH 6.8 was affected by all the variables except the amount of emulsifier. The formulation with a 0.25:4 ratio of drug:ceresine wax and 0.04% of Tween 80 in 600 rpm emulsification speed showed a suitable multiparticulate delivery system for the retarded dissolution of entrapped active ingredients, allowing absorption only in the intestinal tract.