Dissolution efficiency

Practically water insoluble Simvastatin has been accused for being poorly absorbed from gastro intestinal tract. With an aim to improve the solubility and dissolution characteristics of the drug, solid dispersion and surface solid dispersion were prepared by using different water soluble and insoluble carrier at different ratio. Dispersions were made by solvent evaporation technique and undergo drug content test, compatibility by FT-IR, DSC thermal study and in vitro drug release study. FT-IR and DSC thermographs showed the compatibility of the drug and carrier in the incorporated ratio. All the preparations were found to improve the dissolution behavior of Simvastatin significantly compare to the binary physical mixtures and the pure drug. The suitability of solid dispersion and surface solid dispersion technique was evaluated. Also the efficacy of the carriers to improve the dissolution behavior was compared. Tablets were formulated by incorporating dispersions and were subjected to various physical tests including thickness, diameter, hardness, average weight and disintegration time. Their release pattern was compared with compressed matrix of drug and two brand products available in Bangladesh market. Their drug release pattern was further characterized with mean dissolution time (MDT), fractional dissolution time (T50% and T80%) and percent dissolution efficiency. Tablets made of dispersion with HPMC, sodium starch glycolate and croscarmellose sodium were found to have better release rate and extent than the drug and the brand products.

Dissolution is a valuable qualitative tool to asses the biological availability and batch to batch consistency. Discriminative dissolution mediums are highly desirable to differentiate the dissolution profiles of two identical products which are varied in their composition, formulation technique, manufacturing process and site of manufacturing. The objective of present investigation is to develop discriminative dissolution medium for valsartan by using two different marked formulations named as VALZAAR and VALENT. The dissolution studies were performed in four dissolution mediums (0.1N HCl (pH 1.2), pH 4.5 acetate buffer, pH 6.8 phosphate buffer and distill water) at three different agitation speeds (50, 75,100 RPM). Model independent approaches such as difference factor (f1) and a similarity factor (f 2) were used to compare dissolution profiles. Among all the cases in pH 6.8 phosphate buffer at 100 rpm drug releases at faster rate and best suited to maintain sink conditions. Irrespective of other cases pH 4.5 acetate buffer at 50 rpm was considered as a discriminative dissolution medium because of its lesser similarity factor and higher difference factor. From the present experimental investigation the rate of dissolution was found to be influenced by pH of the dissolution medium and speed of the agitation. The usage of 4.5 acetate buffer at 50 rpm was found to be a discriminative dissolution medium for valsartan tablets.