Effect of shape factor on the release rate of drugs from lipid matrices.

It is usually quite difficult to obtain zero order release rate kinetic from matrix system. The release of drug from matrix is usually inversely proportional to the square root of time. It is shown in previous works that the release kinetics from the matrix system are strongly dependent on the matrix geometry. In this work, we aimed at producing zero order release kinetics by changing the shape of matrices. For this purpose, water soluble drug (Paracetamol) and slightly soluble drug (Ibuprofen) in the lipid matrices of hydrogenated cotton seed oil (HCSO) are used. Formulations are prepared in the shape of cylinder, slab, hemisphere and biconvex. In all formulations, the concentration of active material per unit volume is held constant. The rate of release of active material is determined by using the rotating basket dissolution test apparatus. The results are tested for Q-->square root of t and zero order kinetics. As a result, the hemispheric matrices are found to satisfy the requirements for constant release systems for both water soluble and slightly soluble drugs.