Controlled-release technology emerged during the 1980s as a commercially sound methodology. The achievement of predictable and reproducible release of an agent into a specific environment over an extended period of time has much significant merit. It creates a desired environment with optimal response, minimum side-effects and prolonged efficacy. Controlled release dosage forms enhance the safety, efficacy and reliability of drug therapy. They regulate the
drug release rate and reduce the frequency of drug administration to encourage patients to comply with dosing instructions. Conventional dosage forms often lead to wide swings in serum drug concentrations. Most of the drug content
is released soon after administration, causing drug levels in the body to rise rapidly, peak and then decline sharply. For drugs whose actions correlate with their serum drug concentration, the sharp fluctuations often cause unacceptable side-effects at the peaks, followed by inadequate therapy at the troughs (Fig. 2)