Drug penetration into a membrane investigated by photoacoustic and FTIR-ATR spectroscopy

The spectroscopic methods step-scan Fourier transform infrared (FTIR) photo acoustic spectroscopy (PAS) with phase modulation, FTIR attenuated total re flection (ATR) and the ultraviolet (UV) PAS were used to study the dynamics of a model drug (Dithranol) penetration from a semisolid Vaseline formulat ion into an artificial membrane being a skin model. A concentration of the drug at the surface (studied with the FTIR-ATR method) and its variation wi th a depth of the sample (using the PAS technique) were determined. Applica tion of two different spectroscopic wavelength windows i.e. UV and IR light bands, allows one to exclude the possible effect of interactions between t he drug and membrane and light in our measurements. From the methods used a non-invasive insight into the penetration process becomes accessible and t he drug distribution in the membrane can be estimated.