Novel forms of insulin delivery

Abstract

Despite its widespread use, much is wrong with conventional subcutaneous insulin injection. It is more-or-less painful and inconvenient; it delivers insulin slowly with highly inconsistent pharmacokinetics into the peripheral venous system rather than directly to the liver via the portal vein; and, once delivered into the skin, it cannot be "turned off". This review has focused on novel alternative approaches to insulin delivery. The clinically available insulin delivery devices, such as pen injectors and external insulin pumps, are probably underutilized. Pen injectors offer convenience, whereas external pumps offer a basal/bolus approach to insulin delivery unlike that achieved by injections. Of the approaches currently under development, IPPs are closet to general availability. They have been extremely popular in more than 600 patients worldwide, however, an insulin problem has delayed application for their PMA in the United States. Feasibility studies of inhaled insulin, nasal insulin, and oral insulin have produced interesting preliminary findings, with pulmonary delivery for meal coverage with short-acting insulin having perhaps the brightest prospects. Encapsulated islets and biohybrid systems that place live islets into an implanted device are in earlier stages of development. Closing the loop with a continuous glucose sensor will be the only way to achieve truly normal blood glucose homeostasis by directing insulin delivery automatically on demand. Glucose sensors would have many other clinical applications in diabetes management in addition to driving a mechanical delivery system. However, the development of glucose sensing devices has been a formidable technical challenge. Based on an evaluation of current technologic development, glucose oxidase-based, needle-type sensors may become available within the next few years. Clinicians, the research community, and persons with diabetes can join in rejecting the notion that standard regimens of insulin injection do not need to be improved. If there is adequate incentive to continue a broad-based research effort into novel approaches to insulin delivery, the quality of life of persons with diabetes can be improved in the not too distant future.