Verapamil hydrochloride (VPH) was encapsulated using emulsion solvent-evaporation technique. Ethyl cellulose (EC), Eudragit RS (Eud. RS) and cellulose acetate butyrate (CAB) were used as the coating polymers. The dissolution behavior of microspheres was carried out in simulated gastric fluid (SGF). The decrease in the drug/polymer (CAB) ratio led to coarser particle size without any pronounced effect on the release rate. In general, the retardation of drug release after encapsulation was smaller than required.
Different amounts of beeswax were coencapsulated with verapamil HCI in the microspheres based on CAB. A significant retardation was obtained with the increase in the amount of wax used. As the mean size of microspheres increased, the release of drug decreased. Analysis of the release data revealed that the drug release kinetics was dependent on the dissolution medium and microspheres composition. DSC and X-ray analysis of the polymer, drug and drug-loaded microspheres were performed in order to characterize the physical state of the polymer and drug after encapsulation.