Analytical method development and validation of a combination formulation
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Hypertension and dyslipidemia may frequently coexist, and together have an increase in coronary heart disease related events. Combination therapy of rosuvastatin calcium and amlodipine besylate, effective for the control of hypertension by substantially reducing blood pressure and cholesterol levels, can improve its control rates to well above 80% rather than a single pill for hypertension which will control no more than 50% of a hypertensive population. The objective of the present study was to develop and validate a simple, selective and reproducible RP-HPLC method according to the ICH guidelines for the simultaneous estimation of rosuvastatin calcium and amlodipine besylate in their combined dosage forms and for drug dissolution studies. The method involves gradient elution of drugs in a stationary phase of Luna 5μ C18 column (250 mm x 4.60 mm) using a mobile phase mixture of acetonitrile and phosphate buffer of pH 2.5 in the ratio 45:55 % v/v, with a flow rate of 1.5 ml/min in ambient temperature for separation and quantification of the drugs. The injection volume was 10μl and ultraviolet detector was set at 240 nm. Total runtime was less than 9 minutes. Under the above mentioned conditions, the system was found to elute rosuvastatin calcium at approximately 6.08 mins (Assay), 6.17 mins (dissolution) and amlodipine besylate at approximately 2.5 min (dissolution), 2.7 min (assay). Linear regression analysis data for the calibration plots showed good linear relationship with r2= 0.993 with respect to peak area in the concentration range 8 -1.2 μg/ml for rosuvastatin and r2= 0.996 with respect to peak area in the concentration range 4-6 μg/ml concentration of amlodipine. The percent of recovery was found to be in the range of 98-102% for both the drugs. The developed and validated assay method was found to be accurate, precise, robust and specific which allows its adoption for the routine quality control in-vitro dissolution studies of both the pure drug and the combination formulation.