Stimuli-sensitive hydrogels in controlled and sustained drug delivery.

Recently, controlled and sustained drug delivery has become the standard in modern pharmaceutical design and an intensive research has been undertaken in achieving much better drug product effectiveness, reliability and safety. In this regard, many polymers are very useful with majority of hydrogels, which undergo reversible volume and/or sol-gel phase transitions in response to physiological (temperature, pH and present of ions in organism fluids, blood glucose level) or other external (electric current, light) stimuli. This article reviews the main stimuli-sensitive hydrogels and the use of these hydrogels in parenteral, ocular, peroral, rectal, vaginal, nasal, dermal and transdermal drug delivery.