[Photostability of nifedipine]

Photochemical degradation reactions and the chemical structure of the decomposition products were studied in the 1,4-dihydropyridine series for Nifedipine drug substances and for various dosage of it (Cordaflex product family). The efficiency of the used primary and secondary light protection implemented for the Cordaflex retard 20 mg tablet were studied using 48-month long-term stability trials. The dissolution profiles and impurity levels (HPLC) obtained during the whole trial period met the strictest compendial requirements for this dosage form.