Microparticle resins as a potential nasal drug delivery system for insulin

The application of various resins for the nasal delivery of insulin was examined in rabbits. Intranasal administration of human insulin (28 U, 1 mg) mixed with fractionated sodium polystyrene sulfonate powder (an anionic resin with a particle size of 20–45 μm) caused a rapid increase of the plasma insulin level to 413.0±71.7 μU/ml (mean±S.D.) after 15 min, while intranasal administration of insulin alone caused little increase. The blood glucose level decreased from 118.8±18.5 mg/dl to 65.8±13.8 mg/dl at 45 min after administration. These results were superior to those obtained with the unfractionated resin. Styrene–divinylbenzene copolymer (a nonionic resin; 20–45 μm fraction) showed similar enhancement of nasal insulin absorption. In contrast, polyacrylester (a nonionic resin; 20–45 μm fraction) and cholestyramine (a cationic resin) did not promote insulin absorption. These results suggest that some resins may be useful for nasal delivery of insulin.