Controlled drug delivery systems refer to those dosage forms of a drug that are capable of controlling the rate of release of the drug into the body
. Thus, the drug is released at a predetermined rate for a specific period in the body.
Controlled drug delivery systems have several advantages over traditional drug delivery systems and thus, research is going on to find the best controlled drug delivery method.
1.Ease of maintaining optimum therapeutic concentration of drug in the body. The fluctuation of drug levels in plasma is minimized.
2.Predictable and reproducible release rates of drugs. The rate of drug release can be extended to achieve maximum efficacy. Thus, the safety/efficacy ratio of the drug improves.
3.The duration of action of drugs with short half lives (decay fast) can be extended.
4.Better patient compliance because the dosing is not frequent and side-effects of drugs are minimized because the overall dosage is lowered.
5.Wastage of drugs is minimized.
The systems currently used to achieve controlled drug delivery are:
Matrix system: The drug is mixed in a polymer matrix in this system. Thus, the rate of drug release depends on the rate of dissolution of the polymer. These systems are also called Monolith Dissolution Controlled System.
Encapsulation system: Also called Coating Dissolution Controlled System. As the name suggests, the drug is encapsulated inside a coating of polymer. The release rate of drug in these systems depends on the thickness and stability of the coating. The drug is released when the outer coat of polymer dissolves.
Reservoir system: In this system, the drug is contained inside a core of a water insoluble membrane. It is similar to an encapsulation system except that the drug is released by diffusion and not dissolution. The drug diffuses through the membrane into the body.