Optimization, Development and Validation of a Stability Indicating Rp-HPLC Method for Simultaneous Quantification of Amlodipine, Olmesartan and Chlorthalidone in Pharmaceutical Formulations

The present study aimed to develop and validate a simple, rapid, accurate, precise, and stability-indicating RP-HPLC method for the simultaneous estimation of Amlodipine, Olmesartan, and Chlorthalidone in combined tablet dosage forms. The optimized method used a C18 column (250 × 4.6 mm, 5 µm) with Acetonitrile and Potassium Dihydrogen Phosphate buffer (60:40, v/v) adjusted to pH 3.0 as the mobile phase. The flow rate was 1.0 mL/min, detection wavelength was 238 nm, injection volume was 20 µL, and the total run time was 10 min. The drugs showed well-separated peaks at retention times of 2.34, 4.58, and 6.92 min for Amlodipine, Olmesartan, and Chlorthalidone, respectively. The method was validated according to ICH Q2(R2) guidelines. Good linearity was obtained with R² values of 0.9997, 0.9998, and 0.9996, respectively. Recovery was between 99.42% and 100.36%, and precision values were within the acceptable limit of 2% RSD. The LOD values were 0.27, 0.40, and 0.30 µg/mL, while LOQ values were 0.82, 1.21, and 0.91 µg/mL for the three drugs, respectively. Assay results for the marketed tablet were 99.60%, 100.30%, and 99.68% for Amlodipine, Olmesartan, and Chlorthalidone, respectively. Forced degradation studies showed 2.82–9.64% degradation under different stress conditions, with no interference from degradation products. The results confirmed that the method is suitable for routine analysis and stability studies of these drugs in combined pharmaceutical formulations.