A study of photodegradation of drug rosuvastatin calcium in solid state and solution under UV and visible light irradiation: The influence of certain dyes as efficient stabilizers

Photodegradation of rosuvastatin calcium (1) under several radiation wavelengths in solid state and solution in solvents of different polarity has been studied. It was shown that 1 is very sensitive, especially in solution, even to low energy wavelengths and main and almost exclusive degradation pathway includes formation of diastereomeric dihydrophenanthrene derivatives (R,S,R)-2 and (S,S,R)-2. Absolute configurations of isolated diastereomeric photoproducts in forms of respective lactones 3 and 4 have been determined. First partial diastereoselective photocyclization of 1 leading 10.5% d.e. of (R,S,R)-2 over (S,S,R)-2 has been determined in water as a solvent. To prevent photodegradation of 1 in solution use of brown glass is necessary. Solid formulations of 1 are efficiently protected against photodegradation by the presence of combination of dyes such as yellow iron oxide and pink color E122 or β-carotene inside the formulation or tablet coating.