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 st...