Development and Validation of RP-HPLC Method for Azilsartan Medoxomil Potassium Quantitation in Human Plasma by Solid Phase Extraction Procedure

Simple and rapid reverse phase high-performance liquid chromatography (RP-HPLC) method was developed and validated using solid phase extraction (SPE) technique for the determination of Azilsartan Medoxomil Potassium (AMP) in human plasma; detection was carried out by photo diode array detector. Chromatographic separation of the analyte AMP was achieved within 7.5？min by Waters symmetry C18 (4.6 × 250？mm, 5？μm) column, mobile phase was 25？mM ammonium acetate buffer (pH 5.5): acetonitrile 55？:？45？v/v, flow rate was 1.0？mL/min, and the detection was carried out at 254？nm. Calibration curve was linear (r2 > 0.9985) in the range of 1.0–9.0？μg/mL, limit of detection (LOD) and limit of quantitation (LOQ) were 0.150？μg/mL and 0.400？μg/mL, respectively, and intra- and interday deviations were between 1.53–8.41% and 1.78–4.59%, respectively. The overall mean recovery of AMP was 92.35%. No any endogenous constituents were found to interfere at retention time of the analyte. This new RP-HPLC method was successfully validated and may be applied to conduct bioavailability and bioequivalence studies of AMP. 1. Introduction Azilsartan Medoxomil Potassium is chemically named as (5-Methyl-2-oxo-1,3-dioxol-4yl) methyl 2-ethoxy-1-{[2′-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl) biphenyl-4-yl]methyl}-1H-benzimidazole-7-carboxylate monopotassium salt (Figure 1). It is a white crystalline powder which is practically insoluble in water, freely soluble in methanol, dimethylsulfoxide, and dimethylformamide, soluble in acetic acid, slightly soluble in acetone, and acetonitrile and very slightly soluble in tetrahydrofuran and 1-octanol [1]. Figure 1: Chemical structure of lafutidine hydrochloride salt. The US Food and Drug Administration (FDA) has approved Edarbi tablet (Azilsartan Medoxomil Potassium) on February 25, 2011, to treat hypertension in adults. It is available in 80？mg and 40？mg dosages, with the recommended dosage set at 80？mg once in a day [2]. Angiotensin II hormone plays a vital role in activation of renin-angiotensin-aldosterone system as well as in regulation of blood pressure, fluid-electrolyte balance, and also in pathophysiology of hypertension. Activation of type 1 angiotensin receptor which is a member of G protein coupled receptor efficiently controls the numerous effects of AII which are vasoconstriction, secretion of aldosterone and vasopressin and cellular proliferation. So blocking of AII receptor will also block receptor-1, and it will lead to termination of the whole course of action mentioned above; so AII blocker will be helpful in the management of