Barnidipine, a new 1,4-dihydropyridine antihypertensive drug, has shown a photosensitive feature. The complete photodegradation profile was defined in accordance with the ICH international rules (1) on the drug solution, raw material and pharmaceutical formulations. Characterization of the photodegradation products was executed by gas chromatography–mass spectrometry. With a feature common to its congeners, the drug when exposed to light, undergoes oxidation generating a main photodegradation product, represented by the aromatic pyridine derivative, generally termed as dehydro-barnidipine, devoid of any pharmacological activity. Determination of barnidipine in presence of its photoproducts was carried out by using spectrophotometric and chromatographic techniques. The analytes concentrations were linearly correlated with spectral measurements in the first to third order UV derivative spectra through equations obtained by simple and multiple regression analysis. The analytical signals were pointed out by both derivative and zero-crossing procedures. HPLC analysis was able to separate the components and perform detection and quantification of each compound at low levels. The recovery values were estimated ranging from 96 to 101% and the quantitation limit of the photoproducts was found to be equivalent to a total impurity level of 1,2%, with respect to the content of barnidipine. The spectroscopic methods were validated by high performance liquid chromatography analysis. Statistical analysis by t- and F-tests, showed no significant difference at 95% confidence level between the two proposed methods. Both spectrophotometric and chromatographic methods are suitable for a rapid, sensitive and reproducible quality control of commercial samples containing barnidipine. (1) ICH Harmonized Tripartite Guideline, Photostability Testing of New Drug Substance and Products, Fed. Register 62 (1996) 27115-27122.
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