Swelling studies and in vitro release of verapamil from calcium alginate and calcium alginate–chitosan beads

The aim of the present work was to investigate the swelling behavior and the in vitro release of the antihypertensive drug verapamil hydrochloride from calcium alginate and chitosan treated calcium alginate beads. Calcium–alginate beads, chitosan-coated alginate beads and alginate–chitosan mixed beads were synthesized and their morphology was investigated by scanning electron microscopy. The swelling ability of the beads in different media was found to be dependent on the presence of the polyelectrolyte complex between alginate and chitosan, the pH of the aqueous media and the initial physical state of the beads. The results revealed that the encapsulation of verapamil in both calcium–alginate and calcium alginate–chitosan mixed beads exceeded 80%. Considering the in vitro stability of verapamil encapsulating beads, 70% of the drug released from wet and dry plain calcium alginate beads within 1 and 3 h, respectively. The presence of chitosan was found to retard significantly the release from wet beads. However, in the case of dry beads the presence of chitosan had no significant effect on the initial release stage and significantly increased the release on the later stage. The results were analyzed by using a semi-empirical equation and it was found that the drug release mechanisms were either “anomalous transport” or “case-II transport”.