SKIN PERMEATION OF INDOMETHACIN FROM GEL FORMED BY FATTY-ACID ESTER AND PHOSPHOLIPID

We selected 20 fatty-acid esters from cosmetic ingredients and investi gated their suitability as a vehicle for absorption-type ointments usi ng indomethacin (IM) as a model drug. Five fatty-acid ester groups, oc tanoate, isononanoate, myristate, palmitate and stearate, were selecte d. The total number of carbon atoms in the fatty-acid esters ranged fr om 17 to 34, and all of these esters are liquid at room temperature ex cept stearyl caprylate. The solubility of IM was higher in fatty-acid esters containing fewer carbon atoms. The permeation rate of IM from a fatty-acid ester suspension through excised hairless rat skin was pro portional to its solubility in the suspension, i.e. about 1-3 mu g/cm( 2)/h. Gels were then formed from esters by the addition of a hydrogena ted phospholipid. The permeation rate of IM from gels were 4-20 mu g/c m(2)/h which were higher than those from suspensions because IM was pr esent in amorphous state with phospholipid. High permeation rates from gels of fatty-acid esters in which side chains were present on both f atty-acid and alcohol moieties were observed.