[Photostability of antifungal agents. 2. Photostability of polyene antibiotics]

The polyene antibiotics amphotericin B, natamycin and nystatin are rapidly degraded under the influence of light. Amphotericin B as a heptaene has a markedly higher photostability than the tetraenes natamycin and nystatin. With a new HPLC method for the separation of the different polyene components we could perform a quantitative analysis of the photodegradation process. Initially degradation products with unchanged spectrophotometric absorption spectra are formed from each of the three polyene antibiotics. Longer light exposure leads to the subsequent degradation of the polyene structures. This photochemical instability was also detected in various drug products with polyene antibiotics as active ingredient. On direct sun exposure of topically applied polyene antibiotics a pronounced photodeactivation of the drug substances is expected.