PHOTOSTABILITY OF CROSS-CONJUGATED GLUCOCORTICOSTEROIDS IN THE CRYSTALLINE STATE

The light stability of cross-conjugated corticosteroids in the solid state has been investigated and the decomposition rates were determined densitometrically. After 48 h of UV-irradiation (lambda = 254 nm) fluocortolone (F), halometasone (H) and rimexolone (R) decompose between 30 and 51%. Under daylight conditions F, H and prednicarbate (P) show decomposition grades between 43 and 63% after 30 days of irradiation. These are regarded to be photochemically unstable, whereas dexamethasone acetate (DA) in N2-atmosphere and parametasone acetate (PA), triamcinolone acetonide (TA), fluocortolone caproate (FC), methylprednisolone (M) and R in case of daylight are photostable.