Background: Osmotic pump drug delivery systems are one of the most promising and widely developed systems. They are
based on the principle of osmosis and are characterized by a zero-order release pattern independent of the physicochemical properties of
the drug involved and some physiological factors. In the past 30 years, a series of difficulties, such as the very wide solubility range of
different drugs, have been resolved accompanied by the development of various types of osmotic pumps. Furthermore, more advanced
designs have been proposed according to practical requirements.
Methods: We started a systematic references collection on osmotic pump systems through different available databases. Then these information
were analyzed and divided according to different subjects. Finally, we made clear our thought and begun to write it in a logical way.
Results: This review mainly concentrates on five kinds of functional osmotic pumps including technology combined, targeted, chronotherapy-
based, ascending and compound osmotic pumps, involving ways to improve bioavailability and reduce side effects. Special attention
is paid to the application of advanced imaging technologies to study osmotic pumps including the coating process, processing
steps, polymer hydration and changes in the internal structure.
Conclusions: Present-day osmotic pumps not only produce a constant release, but also have the ability to produce adjustable release according
to practical requirements. Hence, technology combined, targeted, chronotherapy-based, ascending and compound osmotic pumps
are a positive development. These latest advances offer various advantages compared with the classic osmotic pump, and enable them to
meet the new needs for clinical use with fewer side effects and improved safety. In addition, following the improvements in the versatility
and complexity of the novel osmotic pump system, conventional assessing parameters may fail to meet the increasing demand for information.
Hence, novel imaging and monitoring technologies have been employed to monitor osmotic pumps from the coating process,
processing steps, and polymer hydration to the changes in polymeric internal structure, which are associated with the different performance
offered by the in vivo action of similar products.