Effect of surfactants on the nasal absorption of insulin in rats

The nasal administration of insulin preparation to rats resulted in dose-dependent hypoglycemia. The absorption of insulin through the nasal mucosa was enhanced when a surfactant, among various non-ionic, anionic and amphoteric surfactants, including the bile acid salts, saponin and peptidelipid (surfactin), was added to the insulin solution. Among the non-ionic surfactants, the addition of an ether type having a HLB(hydrophile-lipophile balance) value from 8 to 14 was found to produce the highest promoting effect on the nasal absorption of insulin. The bioavailability of nasally administered insulin with the surfactant was estimated to be about 30% by comparing the hypoglycemic effect with that obtained after intravenous administration.