[Photoacoustic spectroscopy as a new approach to the determination of the skin penetration of locally applied drugs. Preliminary communication].

Photoacoustic-spectroscopic investigations of the penetration of topically applied drugs into the horny layer of the human skin are reported. By this technique the light absorption of the horny layer and its change due to drug diffusion can be determined in vivo in dependence on depth. Measurements have been performed on a sunscreening agent and on an UVA-absorbing systemic drug after topical application to the forearm.