Distribution of khellin in excised human skin following iontophoresis and passive dermal transport

The aim of this work; was to study in vitro khellin distribution into human skin after passive or iontophoretic transport. The experiments were perfor med on excised human skin, using vertical Franz-type diffusion cells. The e ffects of current application and reservoir pH were studied. At the end of the experiments the skin was sliced thinly and the drug was extracted and a nalyzed by HPLC. The results showed that khellin is able to penetrate throu gh stratum corneum, to reach basal epidermis and upper dermis. The applicat ion time proved to be an important parameter. Current application (30 min; 0.5 mA/cm(2)) with a donor at pH 7.0, favored khellin accumulation even if the drug is not ionized. On the contrary, the use of a formulation at pH 3. 2 inhibited drug accumulation. Leaving the drug reservoir in contact with t he skin for 30 min after current application led to a dramatic increase of khellin concentration. A combination of dermal iontophoresis and passive di ffusion is then a useful technique to govern khellin distribution in the sk in. (C) 1999 Elsevier Science B.V. All rights reserved.