Formulation and in-vitro Evaluation of Oral Captopril Bioadhesive Delivery System

Background: Captopril is considered as the drug of choice in the treatment of hypertension and congestive heart failure. It has a very short duration of action and a biological half-life of 1-2 hr. This requires its administration in 2-3 times daily which is not convenient for the management of a chronic disease like hypertension. Objectives: Captopril is unstable at the alkaline pH of the gastrointestinal tract. Therefore, it is difficult to be delivered orally in a sustained release formulation. This defect can be overcome by using bioadhesive or floating delivery systems which could increase the residence time of the drug in the stomach. Methods: Different formulations of bioadhesive chitosan microspheres containing captopril were prepared using the cross-linking method. Characterization of these microspheres was performed by measuring percent yield, particle size, swelling and bioadhesive properties, drug content and in-vitro release of captopril. Results: Chitosan microspheres prepared from 2% high molecular weight chitosan in acetic acid with 5ml glutaraldehyde and a cross-linking time of 3 hr gave the highest yield percent (83%), the highest entrapment efficiency (55%) and sustained release over 8 hr, compared with other examined formulations of chitosan. The release kinetics from all the prepared microspheres were diffusion-controlled mechanism and the drug release from microspheres was dependent on its concentration. Conclusion: In conclusion, chitosan microspheres with their particle size and release behavior seem to be a good carrier for captopril.