VEHICLE EFFECTS ON IN-VITRO SKIN PERMEATION OF AND STRATUM-CORNEUM AFFINITY FOR MODEL-DRUGS CAFFEINE AND TESTOSTERONE

The effects of Labrasol (LBS) (glycolysed ethoxylated C-8/C-10 glyceri des), Labrafil (LBF) (glycolysed ethoxylated glycerides), Transcutol ( TSC) (diethylene glycol monoethyl ether) and DPPG (propylene glycol di pelargonate) on the flux across excised human skin of the lipophilic t estosterone (TST) and the hydrophilic caffeine (CAF) and on the affini ty of the human stratum corneum for these drugs are compared taking pr opylene glycol (PG) and liquid petrolatum (LP) as reference vehicles. DPPG and LBF enhance CAF flux relative to PG while LBS and TSC increas e the stratum corneum affinity for TST relative to LP. However, the ma terials tested enhance neither the flux of nor the stratum corneum aff inity for both drugs with respect to either reference. On the other ha nd, a saturated solution of DPPG in PG enhances both properties for bo th drugs relative to PG. Such effects are ascribed to the ability of D PPG to interact with the lipid bilayers and to that of PG to promote D PPG penetration into stratum corneum and to create interaction sites i n such a tissue.