Photostability and Phototoxicity of Hydrocortisone acetate

Hydrocortisone acetate is a corticosteroid used systemically for the treatment of rheumatoid arthritis, endocrine disorders and allergic diseases, and topically for dermatoses as an antiinflammatory and antiallergic agent. Its sensitivity to UV light has been studied. Hydrocortisone is rather stable under UVA light (2.5% and 1.5% lysis in PBS and in MeOH, respectively, under 30 J/cm2), but it readily decomposes under 15 J/cm2 of UVB light (70% in PBS, 57% in MeOH, 40% in the solid state and 20% in a commercially available cream). Two main photoproducts have been isolated and characterized. They correspond to the 18\uf061 and 18\uf062-CH3 diastereoisomers formed by loss of 17-\uf062-ketol side chain (necessary for glucocorticoid activity) followed by the 17\uf062-OH oxidation to keto-group. Moreover, Hydrocortisone showed photohemolytic properties under UVB light, partly dependent on the presence of oxygen and mostly on the radical species and stable photoproducts formed during irradiation. No phototoxicity was found under UVA light. Therefore, hydrocortisone acetate must be protected from light during storage and administration to avoid both the phototoxic effects and the reduction of therapeutic activity

Uv-a Photolysis of Khellin - Products and Reaction-mechanism

Photolysis at 365 nm of khellin in various solvents was studied: the degradation rate strongly depends on solvent but not on polarity, since it is related to the singlet oxygen lifetime in each solvent. Eight products were isolated and characterized, some of which had previously been described as coming from chemical oxidation of khellin. Both facts support an oxic pathway for photolysis involving singlet oxygen and leading to unstable intermediates. These are rapidly decomposed by nucleophiles, suggesting possible interference-if they are also formed in vivo-with physiological processes during photochemotherapeutic treatment with khellin

Betamethasone: photolysis and phototoxicity

The photolysis of Betamethasone (1), a synthetic glucocorticosteoid used for the treatment of rheumatic diseases and dermatologic disorders, has been studied both in organic and aqueous solution under UVA and UVB light. The drug decomposes up to 90 % under UVB light (18 J/cm2) and to 40 % under UVA light (30 J/cm2). Four main photoproducts have been isolated by TLC and characterized by NMR and MS analyses. They correspond to: 1a , the byciclo[3.1.0]hex-3-en-2-one rearranged derivative; 1b, the 1,11-oxysteroid derivative ; 1c, the 17-H derivative (formed by loss of 17 \u2013OH) ; 1d, the 17 keto derivative, generated from a Norrish Type I reaction . Bethametasone also shows photosensitizing properties: it is able to induce photohemolysis under UVB (95 %, 1,5 J/cm2) and UVA light (55 %, 30 J/cm2). The isolated photoproducts also photohemolyze the RBC in the order of potency: 1c > 1a > 1b > 1d, thus proving to contribute to the overall photosensitizing properties of Betamethasone. The photostability of the drug was also studied in the solid state and in different pharmaceutical formulations. The presence of additives (such as sodium metabisulphite, phenol) have some photoprotective effect but they do not completely preserve the drug from photolysis. Therefore, both the loss of therapeutic activity and toxicity may be induced when Betamethasone is exposed to light