Recent developments in insulin delivery techniques. Current status and future potential

Although single or multiple daily subcutaneous injections of insulin are the mainstay of insulin delivery techniques, several other methods of insulin delivery are now available or in development, including: (a) continuous subcutaneous insulin infusion by a wearable infusion pump; (b) total or segmental transplantation of a pancreas; (c) transplantation of isolated islet cells; (d) implantation of a programmable insulin pump; (e) oral, nasal, rectal and transdermal mechanisms of insulin delivery; (f) insulin analogues; (g) implantation of polymeric capsules which give continuous or time-pulsed release of insulin; and (h) implantation of a biohybrid artificial pancreas which uses encapsulated islets. Many of these methods of insulin delivery are aimed at achieving a more physiological means of delivery of the insulin, thus to improve glycaemic control and hopefully minimise the secondary complications of diabetes. Techniques of multiple insulin injections and continuous subcutaneous insulin infusion pumps are already in widespread use and are resulting in improved glycaemic control. With the recent increased use of pancreatic transplantation, the rule of establishing euglycaemia will be elucidated in the treatment and prevention of microvascular and macrovascular complications of diabetes mellitus. Despite these advances, the ideal delivery of insulin to patients has yet to be developed. Subcutaneous methods of insulin delivery do not precisely mimic physiological insulin needs and transplantation requires risky immunosuppression. However, the future does look bright as glucose sensors are developed and insulin analogues synthesised.