[Controlled-release drugs: administration routes and formulations].

The notion of controlled release has been known since the 1930s, but was not significantly developed until the 1970s. At that time, Alza introduced the concept of a "therapeutic system" and proposed new pharmaceutic formulations. Over time, the idea became one of controlled drug delivery and today concerns not only one rate of release but also the site of release of the active substance. We present here definitions, fundamentals and advantages and disadvantages of currently marketed systems and provide examples illustrating oral, transdermal and respiratory delivery systems. Current research is also examined.