Sustained-release microcapsules of nitrofurantoin and amoxicillin; preparation, in-vitro release rate, kinetic and micromeritic studies.

In this work, nitrofurantoin and amoxicillin trihydrate microcapsules were prepared by complex coacervation at pH 3.5 using carboxymethylcellulose-gelatin at a weight ratio of 3:7. Release rates were studied as a function of core:wall ratios of microcapsules. Dissolution tests of microcapsules and their tabletted microcapsules were studied in artificial gastric and intestinal media without enzyme using the USP XXII basket method. Release rates were examined kinetically and the ideal kinetic models were estimated for drug release. In addition, the micromeritics of these microcapsules were investigated. In order to standardize the drug powder and the microcapsule product for industrial application, the micromeritic properties of microcapsules were studied by determining their bulk volume and weight, tapping volume and weight, fluidity, angle of repose, weight deviation, particle size distribution, density and porosity. Hausner ratio and consolidation index were also calculated to understand flowability rates of microcapsules when tableting or filling into gelatin capsules. The results indicated that the nitrofurantoin microcapsules need appropriate glidant but the amoxicillin trihydrate microcapsules did not. Moreover, it was observed that the microencapsulation changed the micromeritic properties of the drugs significantly.