Controlled release systems for insulin delivery

Diabetes mellitus is a major cause of mortality in industrialised countries, and insulin has remained indispensable in the treatment of diabetes mellitus since its discovery. Generally, patients with diabetes mellitus need a relatively constant basal insulin supply to mimic a near-normal physiological pattern of insulin secretion. However, as a consequence of very short in vivo half-lifes, poor oral bioavailability and current lack of alternative delivery routes, insulin requires single or multiple daily subcutaneous injections to achieve the desired therapeutic effect, which is inconvenient and painful and with poor patient compliance. Therefore, there is a need for insulin delivery systems that have the capability of releasing the loaded insulin at a controlled and sustained rate for a prolonged period. This review examines recent (2000 - 2004) patents on the controlled release systems for insulin delivery, including those for injectable, oral, pulmonary and transdermal delivery, and the glucose-responsive controlled-release systems.