Effect of Lecithin on Percutaneous Absorption of Drugs. I. Absorption and Excretion of Indomethacin Gel-ointment through Rat Back Skin

Abstract

The effect of benzyl nicotinate (NB) and/or lecithin (PC) on the absorption of indomethacin (IM) through rat back skin were studied by using the 14C-IM gel ointment preparations containing 0.5% NB and/or 2% PC. The absorption of IM estimated from the amount remained both on the plaster and on the surface of skin was increased slightly by NB or PC and significantly by the combination of NB and PC. The radioactivity excreted in the urine and feces was much higher in the preparations containing PC than control 120 h after a topical application for 7 h. Comparing with the pharmacokinetic parameters of IM from control, those from the preparation containing PC were significantly affected; plasma AUC was higher, MRT was shorter, and VRT was larger. NB was fastly absorbed and disappeared from skin, but the disappearance of PC was not so remarkable as NB. The skin level of IM from the preparation containing both NB and PC was higher in the carrageenin induced edema than in the intact skin. It is suggested that the enhancement of transdermal absorption of IM and the acceleration of excretion of IM by PC may be due to the alteration of permeability by the interaction of skin membrane with PC.