ABSORPTION OF TOPICAL TACROLIMUS (FK506) IN-VITRO THROUGH HUMAN SKIN - COMPARISON WITH CYCLOSPORINE-A

Cyclosporin A (CsA) is efficacious in many dermatoses as an oral but n ot as a topical form, while tacrolimus (FK506) has been shown to be ef fective in both forms, As inadequate skin absorption has been proposed as the reason for inefficacy of topical CsA, factors contributing to percutaneous absorption of FK506 and CsA were studied. Partitioning of FK506 and CsA between octanol and water, stratum corneum and water, a nd stratum corneum and isopropyl myristate was determined, Absorption of FK506 and CsA through dermatomed human cadaver skin was determined with in vitro flow-through cells, In partitioning experiments, CsA was more lipophilic than FK506, Both drugs were seen in comparable amount s in skin layers, but FK506 permeated the skin to a greater extent tha n CsA.