A flexible technology for modified release of drugs: multi layered tablets.

Modified release dosage forms offer definite advantages over conventional release formulation of the same drug. Hydrophilic polymers are mainly used for preparation of matrix type controlled delivery systems. The system usually provides nonlinear release profile. The multi-layered matrix system overcomes inherent disadvantages of non-linearity associated with diffusion controlled matrix devices by providing additional release surface with time to compensate for the decreasing release rate. This technology also demonstrates a wide flexibility for various applications. In this article, we review system design, various constructions and formulation parameters of modified release dosage forms.