Evaluation of polyvinyl acetate dispersion as a sustained release polymer for tablets

Kollicoat SR 30D is a unique 30% aqueous dispersion of polyvinvyl acetate stabilized by polyvinyl-pyrrolidone intended for preparation of sustained release products. Detailed evaluation of this polymer dispersion as a sustained release coating for active pharmaceutical ingredients of two diverse classes of drugs was studied. A water insoluble drug (ibuprofen) and a water soluble drug (ascorbic acid) were selected as model active drugs. Ibuprofen was granulated using a GPCG-1 fluid bed processor prior to tableting, to improve the particle size and particle flow properties. In this process a 2(3) factorial design was implemented to evaluate the optimum process parameters such as spray rate, inlet air temperature and the inlet air velocity. The statistical model selected was Y-ijkl = mu + tau(i) + beta(j) + theta(k) +(tau beta)(ij) +(beta theta)(jk) +(tau theta)(ik) +(tau beta theta)(ijk)+ epsilon(ijkl). The factorial design showed that the spray rate, inlet air temperature, and inlet air velocity had a significant effect ( p value < 0.05) on the particle size. Significant improvement was observed in the flow properties of the granules. The granules were coated with Kollicoat SR30D dispersion using top spray method in the fluid bed processor. The dissolution studies showed that the release of ibuprofen decreased with an increase in the coating levels of Kollicoat SR 30 D. In the case of ascorbic acid, preparation of sustained release coated commercial granules was not possible due to the difficulty in coating a highly soluble drug particle. However, the coated granules when compressed into tablets showed some sustainability. Ibuprofen tablets manufactured with coated granules with a 15 g polymer for 300 g batch showed dissolution parameters of t(50) and t(90) at 4.2 hr and 7.5 hr, respectively. An approximate zero-type of release was observed when the polymer content was increased to 45 g for 300 g batch. Ascorbic acid tablets made with coated commercial granules having a total polymer content of 45g per a 500 g batch showed an average dissolution t(50) and t(90) at 1.0 hr and 4.55 hr, respectively. When the total polymer content was increased to 60 g, per 500 g, the average dissolution t(50) and t(90) delayed to 1.40 hr and 7.20 hr, respectively.