nifedipine (nif), a 1,4-dihydropyridine calcium channel antagonist, undergoes photo-degradation to dehydro-nifedipine (dnif) upon exposure to ultraviolet (uv) light and to the nitroso analogue of dehydro-nifedipine (ndnif) when exposed to sunlight or some kinds of artificial lights. nif photo-degradation products do not contribute to clinical activity, thus prevention of photo-degradation of ni...