Simultaneous Determination of Aliskiren Hemifumarate, Amlodipine Besylate and Hydrochlorothiazide in Spiked Human Plasma Using UPLC-MS/MS

A sensitive UPLC-MS/MS method was developed and validated for simultaneous estimation of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) in spiked human plasma using valsartan as an internal standard (IS). Liquid-liquid extraction was used for purification and pre-concentration of analytes. The mobile phase consisted of 0.1% formic acid in ammonium acetate buffer (0.02 M, pH 3.5) and methanol (25: 75, v/v), flowing through XBridge BEH (50 x 2.1 mm ID, 5 mu m) C18 column, at a flow rate of 0.6 mL min(-1). Multiple reaction monitoring (MRM) transitions were measured using an electrospray source in the positive ion mode for ALS and AML, whereas HCZ and IS were measured in negative ion mode. Validation of the method was performed as per US-FDA guidelines with linearity in the range of 2.0-400.0, 0.3-25.0 and 5.0-400.0 ng mL(-1) for ALS, AML and HCZ, respectively. In human plasma, ALS, AML and HCZ were stable for at least 1 month at -70+/-5 degrees C and for at least 6 h at ambient temperature. After extraction from plasma, the reconstituted samples of ALS, AML and HCZ were stable in the autosampler at ambient temperature for 6 h. The LC-MS/MS method is suitable for bioequivalence and pharmacokinetic studies of this combination.