STUDIES ON DRUG-RELEASE KINETICS FROM CARBOMER MATRICES

The objective of this study is to gain a mechanistic understanding of drug release kinetics from directly compressed tablets containing Carbopol 934P and 974P resins. Carbopol resins belong to a family of carbomers which are synthetic, high molecular weight, non-linear polymers of acrylic acid, crosslinked with polyalkenyl polyether. They are currently being used as polymeric matrices for controlling drug release in pharmaceutical tablets. This investigation focuses on the influence of the type of drug and the pH of the dissolution media, along with other factors on the drug release kinetics from carbomer matrices. Directly compressed tablets were prepared using a Stokes single station laboratory press and blends of polymers and lactose with drugs like theophylline, norephedrine HCI, and chlorpheniramine maleate. In vitro drug release studies from the tablets were performed according to USP method II. Drug release rates were obtained by plotting the fraction released versus time and data fitted to the equation: M(t)/M(infinity) = kt(n) The k and n values at pH 1.2 (SGF) and pH 6.8 (SIF) for theophylline, norephedrine hydrochloride, and chlorpheniramine maleate were determined. Our results demonstrate that, even though the tablet formulations were the same, the diffusion processes were different for these drugs. Depending on the type of drug and the pH of the media, the diffusion process occurs as either Fickian, non-Fickian or Case II transport.