HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF NIFEDIPINE AND A TRACE PHOTODEGRADATION PRODUCT IN HOSPITAL PRESCRIPTIONS

A HPLC method is developed for the assay of nifedipine and trace amounts of a photodegradation product in pulverized tablets used in the preparation of hospital prescriptions. After liquid-liquid extraction, nifedipine and its photodegradation product are chromatographed using a reversed-phase system which involves UV detection at 254 nm and the use of two internal standards. The trace photodegradation product in pulverized tablets is determined along with nifedipine by the same procedure. The method is capable of determining 0.5-5.0-mu-g of nifedipine using p-nitronifedipine as the internal standard and 0.01-0.5-mu-g of the photodegradation product using 5-hydroxynifedipine as the internal standard. The standard error is found to not exceed 8.4%. The methods are useful for the study of the disposition or photostability of nifedipine in tablets and pulverized tablets.