Intraduodenal Administration of Biocarrier-Insulin Systems

Successful oral administration of insulin for systemic therapeutic effects has long been a major pharmaceutical challenge. Intraduodenal administration of insulin to rats, free or in a form of carrier-insulin, was the subject of this study. Several erythrocyte-membrane carrier systems (ghosts, vesicles, liposomes-ghosts, and liposomes-vesicles) were tested. Insulin (100 U) was incubated with each of the carriers at 37°C for 24 hr. The carrier-insulin system, insulin solution, sodium chloride solution, or carrier-free insulin was then introduced into the duodenum of anesthetized male Wistar diabetic rats. Blood samples were collected from the tail at different time intervals and then analyzed for glucose content using an o-toluidine method. There was no significant difference in blood glucose concentrations among the control groups. However, ghosts-insulin, vesicles-insulin, and liposomes-vesicles-insulin all showed a statistically significant difference in lowering blood glucose levels when compared to control groups. Liposomes-ghosts-insulin did not show any significant difference from its control group. The results indicate that liposomes-vesicles-insulin was the most efficient in delivering insulin into the circulation in its pharmacologically active form of any other carrier tested. The findings of this study may be of significance in the search for a suitable oral carrier for insulin or perhaps other proteinaceous substances.