Study of the release mechanism of a water soluble drug from hydroxypropyl methylcellulose matrices

ABSTRACT

Directly compressed tablets of pyridoxine HCl in hydroxypropylmethylcellulose [HPMC] matrices containing different polymer ratios, and in HPMC matrices containing various proportions of additives; namely, sodium alginate, pectin, veegum or kaolin or various proportions of an effervescent mixture, were prepared. A double layer floating tablet was also designed. The release characteristics of the tablets were studied in either 0.1 NCl or phosphate buffer [pH 7.4]. The data were fitted into an equation relating release rate constants responsible for diffusional and relaxational processes to determine the relative contribution of the two phenomena on the overall drug release mechanism. The release of the vitamin from the simple HPMC matrix and the one containing an effervescent mixture was slower in 0.1N HCl than in phosphate buffer. The reverse was true in the presence of the additives. The floating tablets in acid medium showed a decrease in the release rate. The formulation containing drug, HPMC, sodium alginate [120.5] can be proposed for further practical application