Achieving zero-order release kinetics using multi-step diffusion-based drug delivery

Zero-order release, in which a drug is released at a constant rate, is the ultimate goal of all controlled-release drug-delivery mechanisms. It leads, in principle, to the best control of plasma concentration and offers several advantages, including improved patient compliance and reduction in the frequency of drug administration. Although there are several techniques that formulation scientists can use to achieve zero-order release, most of them are complex, expensive, time consuming, and difficult to manufacture. In addition, most formulation techniques result in, at best, first-order release. This article provides a novel approach of obtaining the zero-order release of a freely water-soluble active drug by adding methacrylic acid copolymers alone or in combination with cellulose polymers in a tablet matrix. Oral delivery is the most widely-used method for administering therapeutic agents for systemic effects, because it is both convenient for patients and cost effective for drug manufacturers.