Fabrication and in vitro evaluation of bidirectional release and stability studies of mucoadhesive donut-shaped captopril tablets

Abstract

Objective: To obtain controlled release of captopril in the stomach, coated, mucoadhesive donut-shaped tablets were designed.Materials and methods: Donut-shaped tablet were made of different ratios of diluents to polymer or combination of polymers by direct compression method. Top and bottom portions of the tablet were coated with water-insoluble polymer followed by mucoadhesive coating. Time of water penetration, measurement of tensile strength, mucoadhesion studies (static ex vivo and ex vivo wash-off) were taken into account for characterization of respective films. In vitro study has been performed at different dissolution mediums. Optimized batches were also prepared by wet granulation. Stability studies of optimized batches have been performed.Results: The results of time of water penetration and tensile strength indicated positive response against water impermeation. Mucoadhesive studies showed that film thickness of 0.12 mm was good for retention of tablet at stomach. At pH 1.2, optimized batch of tablet made with hydroxypropyl methyl cellulose (HPMC) E15 as binder showed 80% w/w drug release within 4–5 h with maximum average release of 97.49% w/w. Similarly, maximum average releases of 96.36% w/w and 95.47% w/w were obtained with nearly same dissolution patterns using combination of HPMC E5 and HPMC E50 and sodium salt of carboxy methyl cellulose (NaCMC) 500–600 cPs instead of HPMC E15. The release profiles in the distilled water and pH 4.5 followed the above pattern except deviation at pH 6.8. Stability studies were not positive for all combinations.Conclusion: Coated, mucoadhesive donut-shaped tablet is good for controlled release of drug in the stomach.