Purpose: To investigate the effect of co-administration of two absorption enhancing bile salts, sodium glycocholate (NaGc) and sodium salicylate (NaSal), on insulin absorption via intestinal targeted delivery system.

Methods: Insulin (10 IU/kg), associated with and without absorption enhancers (5 % enhancer solution of NaGc or NaSal), was administered to the duodenum, jejunum, and ileum part of the diabetic rat's gastrointestinal (GI) tract by surgical technique. The insulin absorbed from the GI tract was evaluated by its hypoglycemic effect at 45 and 60 min post-administration.

Results: The results showed that insulin formulations containing NaGc or NaSal administered into the duodenum and with little quantity in the jejunum decreased blood glucose levels, compared to the reference formulations (p < 0.05). It was also observed that formulations containing cellulose acetate phthalate (CAP) protectors and enhancers may protect insulin during transit through the stomach for 180 min.

Conclusion: Thus, the results of this study demonstrate that duodenum-specific delivery of insulin with NaGc and NaSal was achievable by oral administration compared to the other parts of small intestine. Furthermore, NaGc has a greater enhancing effect on duodenal, and to some extent, jejunal absorption of insulin.