Photostability study of doxepine hidrochloride

Written by Székely Pál, Gyéresi Árpád

In this paper, we studied the photostability of the doxepine hydrochloride, a dibenzo-oxepine derivate from the tryciclic antidepressant class. The acquos solution of doxepine hydrochloride, was exposed to UV light (Vilber Louromat VL-4-LC lamp), and with this procedure, at well established time intervals, we have determined the content of doxepine by high-pressure liquid chromatography (HPLC). For the separation of doxepine and its degradation products we have used a reversed-phase chromatographic coloumn (Zorbax Extend C₁₈ 250 × 4,5 mm 5μm) and as mobile phase under isocratic conditions a mixture containing potassium dihydrogenophosphate 20 mM (pH=4,5) and acetone (65:35 v/v), with a flowing-rate of 1ml/min, at a temperature of 25°C. Under these analytical conditions the retention time of doxepine was 5,8 minutes, and for the degradation products varied between 2 and 4,5 minutes. For the calibration graphs we used solutions with concentrations between 5 and 250 μg/ml. The correlation coefficient was above 0,995 in all the determinations (using quadratic regression 1/y). From these results we were able to determine the decomposition grade of the doxepine hydrochloride.


Keywords: doxepine hydrochloride, photostability, degradation products, high pressure liquid chromathography.

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