It has been reported that low plasma concentrations are achieved after oral administration of amlodipine. A combination of antihypertensive agents can better selleck chemicals llc control blood pressure and reduce the number and severity of side effects than a monotherapy. Amlodipine and losartan fixed dose combinations have been demonstrated in numerous clinical trails to be highly effective in lowering blood pressure, and suggest that the combined use might be more effective in treating hypertension than a monotherapy.[12,13] One such combination available in the market is Amlopress-Z, (Cipla Limited, Mumbai, India) which is a combination of amlodipine and losartan in a single pill.
As per the literature, several liquid chromatography-tandem mass spectrometric (LC-MS/MS) methods have been reported for the determination of losartan along with its active metabolite, losartan acid, and amlodipine individually in biological samples.[14�C23] To date, no LC-MS/MS method has been reported for the simultaneous determination of losartan, losartan acid, and amlodipine in human plasma. In the present paper, a simple, rapid, and reproducible validated method has been proposed for simultaneous quantification of losartan, losartan acid, and amlodipine concentrations in human plasma without compromising the sensitivity reported earlier for each drug. Indeed, in the present paper, we have achieved a higher sensitivity (2 folds) for losartan and losartan acid. MATERIALS AND METHODS Reagents and chemicals The reference samples of losartan (99.60%), losartan carboxylic acid (99.20%), amlodipine (99.
20%), and irbesartan (99.70%) were purchased form Neucon Pharma Limited, (Goa, India). Chemical structures are presented in Figure 1. HPLC grade of acetonitrile and methanol were purchased form J.T Baker, (Phillipsburg, NJ, USA). Analytical grade formic acid was purchased from Merck Ltd (Mumbai, India). The control human plasma sample was procured from Cauvery Diagnostics and Blood Bank, (Secunderabad, India). Figure 1 Chemical structures of losartan, losartan carboxylic acid, amlodipine and irbesartan (internal standard [IS]) Instrumentation and chromatographic conditions An HPLC system (Shimadzu, Kyoto, Japan), consisting of a binary LC-20AD prominence pump, an auto sampler (SIL-HTc), and a solvent degasser (DGU-20A3), was used for the study.
Aliquots of the processed samples (15 ��L) were injected into the Zorbax XDB-Phenyl column (75 mm �� 4.6 mm; 3.5 micron particle size; Agilent Technologies, Santa Clara, CA, USA), which was kept at room temperature (25��C). The isocratic mobile phase, a 85:15, v/v mixture of methanol and 0.1% v/v formic acid was delivered at 1.0 mL/min. Detection was performed by an Applied Biosystems MDS Sciex API-4000, (Foster City, CA, USA) mass spectrometer in positive GSK-3 ionization mode.