ABSTRACT
Insulin is used in therapy of both type I and type II diabetes. It is the only effi cient treatment for type I diabetes. As most protein pharmaceuticals, insulin are currently delivered by invasive routes of administration including subcutaneous injections (Ramezan and Sharma 2009). The need to fi nd a non-injectable form (i.e.: non-invasive route of administration) has focused on the oral route (Ramezan and Sharma 2009). Apart from safety and patient compliance, oral administration of insulin is of clinical relevance for the treatment of diabetes (Arbit 2004). Indeed, in a healthy human, physiologically secreted insulin from pancreas enters portal circulation fi rst and inhibits the hepatic glucose production. In this process, insulin undergoes a metabolism in the liver to a signifi cant extent (more than 50%) and thereby the excess glucose is converted and stored in the form of glycogen. Thereafter, insulin not used by the liver fi nds its way to the peripheral circulation. This mechanism reduces the chance of hypoglycemic effect. This is in contrast with the distribution of exogenous insulin obtained after subcutaneous injection to diabetic patients. In this case, insulin distributes fi rst in the peripheral circulation increasing risks of hypoglycemic effects and being ineffective to deliver the required amount of insulin to the liver to maintain their normal physiological function in
glucose metabolism (Arbit 2004). Although oral administration of insulin is indisputably the best route of administration, all efforts put to develop suitable delivery formulation since its discovery remained unsuccessful because peptides and protein drugs are degraded in digestive media and are not absorbed as intact molecules by the intestinal epithelium (Lee and Yamamoto 1989). On the basis of the physiology, challenges to oral delivery of peptide and protein drugs include enzymatic degradation and poor permeation across the gastro intestinal tract (GIT) (Lee and Yamamoto 1989).
