Matrices of water-soluble drug using natural polymer and direct compression method

The objective of this research was to find an optimum Carrageenan matrix formulation with the desired drug release and physical properties prepared by direct compression. In order to achieve this, matrices containing 10% theophylline, different Carrageenan level, and different excipient were prepared and evaluated. A selected matrix containing 40% Carrageenan and lactose fast flo was tested for dissolution in three different dissolution media (distilled water, 0.1 N HCl, and phosphate buffer pH 7.4). The same formulation was also tested for dissolution at 50 rpm, 100 rpm, and 150 rpm, and using different dissolution apparatus (Apparatus 1 and 2). All matrices showed a decrease in drug release as the polymer level was increased. Only Avicel PH-101 did not show any significant difference between matrices prepared with 30% and 40% polymer. At 10% polymer level, it appears that the type of diluent used controls the drug release. However, at high polymer level, 30% and 40%, it appears that the polymer level controls the drug release. Phosphate buffer pH 7.4 and 0.1 N HCl increase drug release and appear to increase Carrageenan solubility and decrease gel formation. Also, as the rotational speed of the apparatus was increased, the integrity of the gel layer was decreased, and the release of drug was increased. The drug release from Carrageenan matrices appears to follow the diffusion model for inert matrix up to 90 min. After 90 min, the drug release follows a zero-order model. This study demonstrated that matrices using Carrageenan can be successfully prepared by direct compression.