Drugs must be delivered in a constant concentration for maximum benefit and safety. The rate of both beneficial reactions and unwanted even dangerous side reactions increase as the concentration of a drug increases. Drugs are administered at levels adjusted to maximize the beneficial reactions. It is desirable to release drugs at a constant rate, thereby maintaining drug concentration within the therapeutic range and eliminating the need for frequent dosages.

Drugs may be administered as "Controlled-release" formulations. The rate of release of the drug depends on the rate of reaction of the coatings or the rate of transport of the drug through a membrane or film. New methods of releasing drugs are under development using the new techniques for controlling the rate of the release process.

Two major type of processes are used. In one type, the drug is imbedded in a polymer matrix which dissolves or allows the drug to diffuse out. In the other type, the drug is enclosed in a reservoir by a membrane. Controlled release drugs.

Productions of coatings may be made by several different processes including a spray process which works for many diverse types of compounds.