Effect of Microencapsulation on Photo-Stability of Nifedipine

Nifedipine (nif), a 1,4-dihydropyridine calciwn channel antagonist, undergoes photodegradationto dehydro-nifedipine (dnif) upon exposure to ultraviolet (uv) light and to thenitroso analogue of dehydro-nifedipine (ndnif) when exposed to sunlight or some kinds ofartificial lights. nif photo-degradation products do not contribute to clinical activity, thusprevention of photo-degradation of nif formulations is very important. large differencesin photo-stability between bioequivalent nif products could potentially result in thetherapeutic failure of unstable preparations . the aim of this study was to evaluate the effectof microencapsulation on nifedipine photo-stability. four different microspheres of nifedipinewere prepared using ethyl cellulose, ethyl cellulose plus titaniwn oxide, pectin and gelatin.microspheres were exposed to fluorescent light and the content ofnif, dnif and ndnif foreach product was measured using a specific and sensitive reversed phase high-pressure liquidchromatography (hplc) method to determine the extent of photo-decompo sition . in addition,photo-degradation of pure nif powder was compared with acidic and buffer solution of nif.solution of nif degraded in one day, while microencapsulation of nif prevented the photodegradationfor up to six days against light exposure. therefore, it may be concluded thatpresent microencapsulation method without using other compounds such as opaque materialsdo not provide enough protection.