OBJECTIVE To study the effects of various
penetration enhancers on the sublingual
absorption of insulin in rats. METHODS
Several absorption enhancers were selected to be co-administered with insulin sublingually in rats. The
sublingual absorption of insulin was calculated by its pharmacological bioavailability (PA%) compared to subcutaneous!y administered insulin solution. The effects of
penetration enhancers on the structural properties of the sublingual membrane of rats were investigated by Fourier Transform Raman Spectroscopy, Circular Dichroism and Fluorescence Polarization in vitro. RESULTS The permeability of insulin significantly increased compared to control after co-administration with Brij35, chitosan and egg lecithin. After being treated with Brij35, egg lecithin and chitosan, not only the fluidity of sublingual lipid membrane increased but also the conformation of the membrane protein loosed. The investigated penetration enhancers produced different effects. CONCLUSION Penetration enhancers can change the fluidity of membrane lipid and the conformation of membrane protein in certain degrees, and increase the sublingual absorption of insulin.