3(3)-FACTORIAL DESIGN-BASED OPTIMIZATION OF THE FORMULATION OF NITROFURANTOIN MICROCAPSULES

A microcapsule form of nitrofurantoin was prepared by a simple coacerv ation method with carboxymethylcellulose and aluminium sulfate. 3(3) f actorial design was performed for three independent variables, namely, the particle size of the drug, the size of the microcapsules and the pH of the dissolution medium. The dissolution tests with the formulate d microcapsules were carried out according to the United States Pharma copeia XXII rotating basket method at pH 1.2, 5, and 7.5, which repres ent the pH of gastrointestinal fluids. Release data were examined kine tically and the ideal kinetic models were estimated and t(63.2) values obtained from RRSBW distribution were used in the factorial design ex periment. The influence of the independent variables on the dissolutio n of nitrofurantoin microcapsules could be expressed as the pH of the dissolution medium > particle size of the microcapsule > particle size of nitrofurantoin. The other aim of this study was to evaluate microc apsule formulation in terms of the criteria with a minimum of experime nts. Our findings suggest that dosage forms which comply with the phar macopoeia criteria for dissolution can be prepared and selected by fac torial design.