ABSTRACT
As described in Chapter 1, the early years of drug delivery research (from about 1950 to 1980) saw the development of various mechanisms to achieve controlled drug release. The principal physical approaches to achieve controlled release were based on diffusion-and dissolution-control. Osmotic pressure and ion-exchange mechanisms were also used. Technologies at this time included sustained-release, once-a-day, formulations for oral delivery, and transdermal patches suitable for daily or weekly administration. The thrust of the research at this time was based on adjusting the physicochemical properties of the formulation, which resulted in the desired sustained-release pharmacokinetic proles in vivo. This research was highly successful and resulted in the introduction of a large number of commercial products.
