Challenges and recent advances in the subcutaneous delivery of insulin.

INTRODUCTION: The morbidity of diabetes mellitus is increasing, and subcutaneous injection of exogenous insulin is well established as an effective therapeutic strategy for reducing complications associated with the disease. However, the pain that accompanies repeated injections is an important drawback, and can detrimentally affect the adherence to therapy. Recently, there have been great improvements in injection devices and techniques, including the development of microneedle systems and quantitative injection technologies, which have increased the accuracy of injection, decreased leakage of insulin to the skin surface, and reduced pain. Areas covered: This review highlights some limitations of current techniques for the injection of insulin and its analogs, and describes new methodologies and strategies that have been developed in an attempt to overcome these limitations. Furthermore, novel technologies currently under development that are potential future prospects for insulin delivery are discussed. Expert opinion: New technologies have provided easier and well-tolerated treatment regimens for diabetes patients. However, to further improve patients' satisfaction, self-regulated insulin delivery, automatic adjustment of needle length, memory function to the injection device, use of novel materials could be introduced into insulin injection. Intelligent control of insulin delivery and soluble microneedle arrays may be important areas of future research.