Measuring the uptake of Azone into excised human stratum corneum from thin polymer films

The extent of uptake of Azone into excised human stratum corneum from thin polymer films has been measured using a sandwich model. With poly(dimethyl)siloxane, an Azone loading of the stratum corneum of 6-7% w/w was achieved. With Eudragit NE30D, a loading of less than 1% was reached. The extent of uptake into the stratum corneum and acceptor layers of the sandwich model depended on the Azone content of the films. The resulting enhanced uptake and flux of diazepam through the stratum corneum membrane into a polymeric acceptor layer corresponded closely to the amounts of Azone taken up and their known enhancing effects. The uptake of diazepam from the poly(dimethyl)siloxane films was ten times larger than that from Eudragit NE30D films. The extent of uptake is, therefore, controlled by the rate of release from the polymer and partitioning at the interface.