Over the past few decades, significant medical
advances have been made in the area of drug delivery
with the development of controlled release
dosage
forms. There are large variety of formulations
devoted to oral controlled drug release, and
also
the varied physical properties that influence
drug
release from these formulations. The release
patterns
can be divided into those that release drug
at
a slow zero or first order rate and those that provide
an initial rapid dose, followed by slow zero or
first
order release of sustained component (1). The
purpose
of the controlled release systems is to maintain
drug concentration in the blood or in target tissues
at a desired value as long as possible
(2). In
other words, they are able to exert a control on the
drug release rate and duration (3). For this purpose,
generally, controlled release system initially release
part of the dose contained in order to attain rapidly
the effective therapeutic concentration of the drug.
Then, drug release kinetics follows a well defined
behavior in order to supply the maintenance dose
enabling the attainment of the desired drug concentration.
In the light of wide versatility of application of
controlled release formulations, in the field of medical
sciences, they are unavoidable tools for the
exploitation
of the modern concept of therapeutic