Stress Degradation Studies and Kinetic Determinations of Duloxetine Enteric-Coated Pellets by HPLC
Abstract A stability-indicating HPLC assay method was developed for the quantitative determination of duloxetine (DLX) in a pharmaceutical dosage form in the presence of its degradation products, and kinetic determinations were evaluated in acid conditions and UV-C radiation exposure. Chromatographic separation was achieved by use of an ACE<sup/> C18 column (250 4.0 mm id, 5 m particle size). The mobile phase was prepared by mixing aqueous 50 mM potassium phosphate buffer (pH 6.0 containing 0.3 triethylamine) and acetonitrile (60 40, v/v). DLX was rapidly degraded in an acid medium and in the presence of hydrogen peroxide and UV-C radiation; it was more stable in alkaline medium. The described method was linear over a range of 4.014.0 g/mL for determination of DLX (r = 0.9998). The precision was demonstrated by the RSD of intraday (0.791.07) and interday (0.85) studies. The mean recovery was found to be 100.56. The acid degradation of DLX in 0.1 M HCl solution showed an apparent zero-order kinetics (k = 0.177 g/mL/min), and the photodegradation demonstrated an apparent first-order kinetics (k = 0.082 g/mL/min). The developed method was found to be simple, specific, robust, linear, precise, and accurate for the determination of DLX in enteric-coated pellets.