ABSTRACT
Oral drug delivery is the most widely utilized route of administration among all the routes that have been explored for systemic delivery of drugs via pharmaceutical products of different dosage form and this oral route provides maximum active surface area among all drug delivery system for administration of various drugs. The attractiveness of these dosage forms is due to awareness of toxicity and ineffectiveness of drugs when administered by oral conventional method in the form of tablets and capsules. Usually, conventional dosage form produces wide range of fluctuation in drug concentration in the bloodstream and tissues with consequent undesirable toxicity and poor efficiency. The maintenance of concentration of drug in plasma within therapeutic index is very critical for effective treatment. These factors as well as factors such as repetitive dosing and unpredictable absorption lead to the concept of oral modified drug delivery systems like Sustained release, prolonged release, modified release, extended release. These formulations are used to identify drug delivery systems that are designed to achieve or extend therapeutic effect by continuously releasing medication over an extended period of time after administration of a single dose. This review describes the basic information regarding modified release dosage form like designed to release their medication in controlled manner, criteria for selecting modified release dosage form and factors influencing the dosage and release pattern.
