EQUILIBRIUM SWOLLEN HYDROGELS IN CONTROLLED RELEASE APPLICATIONS.

Controlled released systems represent a relatively new development that evolved out of a continuing need to prolong and better control drug administration. In conventional drug delivery modes such as a spray, an injection, or the taking of a pill, each time a person takes medicine, the drug concentration in the blood rises, peaks, and then declines. Since each drug has a therapeutic range above which it is toxic and below which it is ineffective, the plasma drug concentration in any patient at a particular time depends on compliance with the prescribed routine. This is particularly problematic if the toxic and minimum effective levels are close together. The goal of a controlled release system is to maintain the drug concentration between these two levels for a prolonged time using a single dosage form.