WAVELENGTH DEPENDENCY OF PHOTODEGRADATION PROCESSES OF DRUG SUBSTANCES

Photodegradation of drugs is largely influenced by the wavelength of t he absorbed light. For a systematic investigation of the wavelength de pendency of photodegradation, artificial light sources with different light filters can be used. Drug substances with absorption maxima in t he shorter UV band (e.g. tioconazole, naftifine, ketoconazole or terco nazole) are much more affected by light filters than drug substances w ith absorption maxima in the near UV and visible band like nifedipine or amphotericine B. Unfiltered light from a xenon lamp has UV radiatio n in a range that is not found in the natural day light spectrum. In o ur investigations, the use of this shortwave light did not lead to the formation of any artefacts. In addition to the light source the packa ging material plays an important role in photodegradation processes. F or reasons of photoprotection, photolabile drug solutions are frequent ly shipped in amber glass bottles. However we could demonstrate, that the stabilizing effect of amber glass as only means of photoprotection is not satisfactory for highly photolabile drug substances like molsi domine.