Effective intestinal absorption of insulin in diabetic rats using a new formulation approach

Insulin injected intra-jejunally together with the non-ionic surfactant cetomacrogol was effective in streptozocin-induced diabetes in the rat, as measured by the hypoglycaemic effect. The reduction in blood sugar was maximal at about 2 h after administration but continued at a high level for the 4 h of the experiment. No hypoglycaemic effect was observed in controls injected with insulin or saline alone. Intestinal absorption of insulin has thus been effected by the addition of cetomacrogol, which appears to enhance membrane-permeability to insulin rather than to function as a protective agent preventing insulin degradation, as in liposome-encapsulation. In support of this, a significant hypoglycaemic action was still obtained when the insulin injection was given half-hour after that of the cetomacrogol, both intra-jejunally. Furthermore, oral administration of the surfactant followed by intra-jejunal injection of the insulin also gave a hypoglycaemic effect. The use of this agent to enhance insulin absorption offers the possibility of a new approach to oral insulin therapy.