New strategies to improve the intranasal absorption of insulin.

Recently, intranasal delivery of insulin as an alternative route of parenteral administration has been widely studied because it bears close resemblance to the 'pulsatile' pattern of endogenous insulin secretion during meal time. However, insulin is not well absorbed through nasal mucosa because of its large molecular size, hydrophilicity and low permeability through the membrane. This review describes the main barriers preventing nasal insulin absorption, and special attention is given to new approaches to improve the intranasal absorption of insulin, including the application of new safe absorption enhancers and the use of appropriate delivery systems. It seems that bioadhesive delivery systems or water-insoluble powders with absorption enhancers are the most promising methods for intranasal delivery of insulin.