Conventional dosage forms deliver their active ingredients at rates that are highest intially and decline steadily therafter. Repetitive dosing with such dosage forms causes a sawtooth pattern of peaks and troughs in the concentrations of the agents in blood and tissues.
Hence, the development of systems designed to control the rate of drug release into the body. Such systems would be expected to be most useful for:
a) Drugs used in a chronic or a symptomatic disease where compliance may be poor.
b) Drugs with a narrow therapeutic margin.
c) Drugs with short half-lives necessitating frequent dosing with coventional dosage forms.
Drug delivery systems can be divided into six groups:
1) Physically - Controlled, 2) Chemically - modified, 3) Osmotically - Controlled, 4) Diffusion Controlled, 5) Mechanically - Controlled, 6) Targeted drug delivery.
In this article after introducing most important novel control drug delivery systems, advantages, and disadvantages of these systems has been described brifley.