[Transdermal iontophoresis of insulin: effect of penetration enhancers on blood glucose level in diabetic rats].

The effects of many usual penetration enhancers such as azone (AZ), oleic acid (OA), poloxamer 188 (POL 188) and propylene glycol (PG) on the blood glucose level in diabetic rats after transdermal iontophoresis of insulin were studied. The change of blood glucose level (D%), defined as the percent ratio of the concentration of blood glucose in rats after the iontophoretic application of insulin to that before administration of insulin, was used to present the data. The results showed that following iontophoretic application of insulin for 3 h, the D% in diabetic rats treated with 100% AZ and 5% AZ/PG was 38.58% and 25.28% respectively, and the D% in diabetic rats untreated with enhancers was 45.48%. The D% in diabetic rats treated with 100% OA, 10%-OA/PG, 10% POL 188/PG and 100% PG was 66.28%, 60.47%, 76.75% and 57.93% respectively. So, AZ showed a synergistic effect on the ability of iontophoresis to promote skin permeation of insulin, and PG further increased this effect. The combination of AZ, PG and iontophoresis increased the permeation of insulin significantly. OA, POL 188 and PG did not display synergistic effect on iontophoresis enhancement. The combination of iontophoresis and some enhancers provided a novel idea and possibility for the administration of polypeptide drugs.