Development and Validation of a UHPLC Method for the Simultaneous Estimation of Hydrochlorothiazide and Amlodipine in Solid Dosage Forms

Abstract

Background: Hypertension, a leading global cardiovascular risk factor, is commonly managed with combination pharmacotherapy. Hydrochlorothiazide (HCT), a thiazide diuretic, and Amlodipine (AML), a calcium channel blocker, are frequently co-prescribed in fixed-dose tablet formulations to achieve optimal blood pressure control. Despite their widespread co-administration, a validated Ultra-High-Performance Liquid Chromatography (UHPLC) method for the simultaneous quantification of both drugs in solid dosage forms was not available in the published literature at the time of this investigation. Methodology: A UHPLC method was developed 
and validated on an Agilent system using a C8 column (4.6 mm × 50 mm, 3 µm) operated under isocratic conditions. The mobile phase consisted of 0.02 M potassium dihydrogen orthophosphate buffer (pH 3.0) and acetonitrile (60:40, v/v) delivered at 0.5 mL/min. Detection was performed at 230 nm with an injection volume of 2 µL. Validation was executed in accordance with ICH Q2(R1) guidelines, encompassing system suitability, specificity, linearity, precision, accuracy, and robustness. Results: Hydrochlorothiazide and Amlodipine were resolved at retention times of 1.810 min and 2.911 min, respectively, within a 5-minute run. Linearity was established over 50–150% of the nominal concentration; correlation coefficients were R² = 1.0000 (HCT) and R² = 
0.9993 (AML). Assay recovery values were 100.33% (HCT) and 100.07% (AML). Repeatability %RSD values were 0.16% and 0.07%, respectively. Mean accuracy recoveries ranged from 100.60–101.28% (HCT) and 99.57–100.97% (AML). All robustness parameters remained within acceptance criteria under deliberate variations in flow rate and detection wavelength. Conclusion: The proposed UHPLC method is rapid, precise, accurate, and specific for the simultaneous estimation of hydrochlorothiazide and amlodipine. It satisfies ICH validation requirements and is suitable for routine quality control analysis in pharmaceutical manufacturing settings.