Recent Updates on Novel Approaches in Insulin Drug Delivery: A Review of Challenges and Pharmaceutical Implications

Diabetes mellitus, a metabolic disorder of glucose metabolism, is mainly associated with insulin resistance to the body cells, or impaired production of insulin by the pancreatic β-cells. Insulin is mainly required to regulate glucose metabolism in type 1 diabetes mellitus patients; however, many patients with type 2 diabetes mellitus also require insulin, especially when their condition cannot be controlled solely by oral hypoglycemic agents. Hence, major research is ongoing attempting to improve the delivery of insulin in order to make it more convenient to patients who experience side effects from the conventional treatment procedure or non-adherence to insulin regimen due to multiple comorbid conditions. Conventionally, insulin is administered via subcutaneous route which is also one of the sole reasons of patient's non-compliance due to the invasiveness of this method. Several attempts have been done to improve patient compliance, reduce side effects, improve delivery adherence, and to enhance the pharmaceutical performance of the insulin therapy. Despite facing substantial challenges in developing efficient delivery systems for insulin, vast research studies have been carried out for the development of smart delivery systems to deliver insulin via ocular, buccal, pulmonary, oral, transdermal, as well as rectal routes. Therefore, the present review was aimed to overview the challenges encountered with the current insulin delivery systems and to summarize recent advancements in technology of various novel insulin delivery systems being discovered and introduced in the current market.