MECHANISTIC STUDIES ON PHOTOLYTIC DEGRADATION OF NIFEDIPINE BY USE OF H-1-NMR AND C-13-NMR SPECTROSCOPY

To understand the photolytic degradation of nifedipine (I), a method based on H-1-NMR and C-13-NMR spectroscopy has been used for the simultaneous determination of nifedipine and its decomposition products, 4-(2-nitrosophenyl)pyridine (II) and 4-(2-nitrophenyl)pyridine (III) homologues. The H-1-NMR technique has been used quantitatively in photodecomposition studies of nifedipine in solid form and in solution, however, the C-13-NMR method is used for confirmatory identification of decomposition products. The extent and mechanism of photolytic degradation were investigated as a function of concentration, solvent polarity, light intensity and irradiation time in solution. The degradation of bulk drug was also studied in detail under different light conditions.