Photostability Determination of Commercially Available Nifedipine Oral Dosage Forms in Iran

Nifedipine (NIF) a 1, 4-dihydropyridine calcium channel antagonist, undergoes photodegradation to nitroso analogues of dehydronifedipine (NDNIF) when exposed to sunlight. Photodegradation products of NIF have no clinical activity, so different formulations of NIF must remain unchanged. If NIF preparations become unstable in exposure to light, they could cause therapeutic failure. The present study was carried out in order to investigate the photostability of commercially available NIF products, in Iran. Three oral NIF formulations available in Iran were studied using indirect sunlight (daylight) and continuous artificial light exposure extending over a period of 12 weeks. The extent of photodecomposition of NIF was determined using a specific reversed phase high performance liquid chromatography (HPLC) method. NIF photodegradation was measured using both pure NIF powder as well as a methanolic NIF solution to determine differences in the effectiveness of artificial light and natural indirect sunlight sources used in this study. All the tested NIF formulations were likely to be photostable up to at least 12 weeks of continuous artificial and natural day light exposure, compared with pure NIF powder and methanolic solution. Photodegradation of NIF powder and methanolic solution exposed to indirect sunlight was faster than the artificial light