Determination of ranolazine hydrochloride in rat urine and study on its gender-related metabolism by RP-HPLC

Aim: To develop RP-HPLC method for simultaneous assay of ranolazine and its metabolites in rat urine and study gender-related metabolism in rats. Methods: Taken methimazole as the internal standard, the samples were alkalized with 0.1 mol/L Na₂CO₃ and extracted with diethyl ether. The upper layer was dried in water-bath and the residue was then reconstituted with 100 μL of the mobile phase and 20 μL were taken for HPLC use. Chromatography was performed on a Lichrospher C₁₈ column (250 mm × 4.6 mm ID, 5 μm), using the mobile phase which consisted of methanol and 1 mmol/L ammonium acetate (pH 4.3) and was operated in the mode of gradient elution with a flow rate of 1.0 mL/min. The eluent was monitored at the wavelength of 271 nm. Results: Calibration curves were linear over the concentration range of 6.25-400 μg/mL. The intra-assay and inter-assay variability values were less than 9.3%. The extraction recovery of ranolazine from urine was in the range of 98.5%-101.0%. Concluson: The established HPLC method is simple, accurate, sensitive and applicable for the study of geneder-related ranolazine metabolism.