Study of Photostability of Finasteride, Diclofenac and Naproxen Through Exposure of Simulated Sunlight and Evaluation of Packaging Photoprotection of These Drugs

The intrinsic photostability characteristics of pharmaceutical active substances and medicinal products should be evaluated to demonstrate that, as appropriate, light exposure does not result in unacceptable change. The photostability of Finasteride, Diclofenac and Naproxen was studied. The irradiation of the samples was performed according to the conditions suggested by the ICH Guidelines [1] for photostability testing by using a special lamp that reproduces the natural sunlight. The exposition of substances was carried out both as active pharmaceutical ingredients, dissolved in suited solvents, than as solid dosage forms. The concentration of the pharmaceutical active substances was monitored by HPLC. A residual concentration value of 57% of Finasteride, after 90 hours of exposition at 600 W/m of light power, was still present, versus a residual value of just 12% for Diclofenac and 9% for Naproxen measured at the same time.