Photodegradation monitoring of amlodipine by derivative spectrophotometry.

A derivative spectrophotometric method for the simultaneous determination of amlodipine and its pyridine photodegradation product has been developed. The analytes concentrations were linearly correlated with spectral measurements in the 3rd order UV derivative spectrum through equations obtained by simple and multiple regression analysis. The recovery values were estimated to range from 95 to 99% and the quantitation limit of the photoproduct was found to be equivalent to an impurity level of 1%, with respect to the content of amlodipine. The method could usefully be applied to routine quality control of pharmaceutical formulations containing amlodipine.