Bioadhesive matrix as controlled release dosage form for verapamil hydrochloride - Effect of the types and percentages of polymers on the release profile of the drug

The effect of different swelling and adhesive polymers on the mechanism of release and the dissolution profile of verapamil hydrochloride from tablets was studied. Polymers investigated in this study include sodium carboxymethyl cellulose (Na-CMC), hydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose (HPC) and poly(acrylic acid) (PAA). Tablets were formulated to contain 240 mg of verapamil hydrochloride and an increasing percentage of each of the previously mentioned polymers including 25, 50, 75 and 100 % of the total matrix weight (260 mg). Microcrystalline cellulose was used to complete the weight of the matrix to 260 mg and to aid in the direct compression of the tablets. Dissolution data were analyzed to determine the mechanism of drug release and the time for 50 % of the drug to be released (t(50%)) was calculated. The effect of the previous polymers and their percentage on the tablets' tensile strength and swelling index was also studied. Both the type of the polymers and their percentages in the matrix affected the mechanism and the rate of drug release. At low percentages of the polymers the release mechanism was variable between diffusion and first-order kinetics depending on whether the tablets are disintegrating or non-disintegrating in nature. At these concentrations PAA showed the highest retardation effect on the rate of drug release followed by HPMC, then Na-CMC and finally HPC. Using 100 % of the polymers, the release of the drug followed a Fickian diffusion mechanism from all matrices. The drug release was mostly retarded by HPC, followed by PAA and HPMC and finally Na-CMC.