A brief review on recent advances of extended release technology employed to design the oral dosage forms

Abstract

The benefits offered by modified release systems include reduced dosing frequency with improved patient compliance, better and more uniform clinical effects with lower incidence of side effects and possible enhanced bioavailability. Characteristics of a modified release system as stated by USP is “The drug release characteristics of time, course and / or location are chosen to accomplish therapeutic or convenience objectives not offered by conventional dosage forms”  [1]. This includes technologies that modify the site of drug delivery. Extended release dosage forms extend the life of a drug so that dosage regiment shifts from 3 times a day dosing just once or twice a day. The successful formulation of a modified release device requires a comprehensive understanding of the mechanism of drug release from the macroscopic effects of size, shape and structure through to chemistry and molecular interaction. Multiparticulate dosage forms shown to be less prone to food effects than monolithic and is often the preferred formulation for extended and / or delayed release. Extended release drug formulation is conventionally produced as compressed tablets by hydrogel tablet technology. To produce these extended release tablet dosage forms, active ingredient is conventionally compounded with cellulose ethers like methylcellulose, ethyl cellulose or hydroxyl propyl methylcellulose with or without excipients and the resulting mixture is pressed into tablets. When the tablets are orally administered, cellulose ethers in the tablet swell upon hydration from moisture in the digestive system, thereby limiting exposure of active ingredient to moisture. As the cellulose ethers are gradually leached away by moisture, water more deeply penetrates the gel matrix and the active ingredient slowly dissolves and diffuses through the gel, making it available for absorption by the body. An appropriately designed controlled release drug delivery system can be a major advance towards solving problems concerning the targeting of a drug to specific organ or tissue and controlling the rate of drug delivery to the target sites. The development of the oral controlled release system has been a challenge to formulation scientists due to their inability to restrain and localize the system at targeted areas of the gastro intestinal tract. Matrix type drug delivery systems as carriers for the active ingredients are interesting and promising option in developing an oral controlled release system. Tablets are the preferred dosage form for many drugs and are still the most widely used formulations for both new and existing modified released products.