Dual Wavelength Spectrophotometric Method for Simultaneous Estimation of Atorvastatin Calcium and Felodipine from Tablet Dosage Form

Atorvastatin calcium (ATR) and felodipine (FEL) are beneficial in combination for elderly people in management of hypertension and atherosclerosis. Aim of present study is to develop simple, accurate, and precise method for simultaneous quantitative estimation of ATR and FEL from combined tablet dosage form. Method involves simultaneous equation, using acetonitrile—double distilled water (70？:？30)—common solvent showing absorption maxima at 245 and 268？nm. Calibration curves determination for both drugs has been carried out in 0.1？N HCl, phosphate buffer pH 6.8, and acetonitrile (ACN)—water (70？:？30？V/V). Linearity range was observed in the concentration range of 2 to 12？μg/mL for FEL and 20 to 100？μg/mL for ATR. Percent concentration estimated for ATR and FEL was 100.12 ± 1.03 and 99.98 ± 0.98, respectively. The method was found to be simple, economical, accurate and precise and can be used for quantitative estimation of ATR and FEL. 1. Introduction Atorvastatin (ATR) is chemically described as [R-( , )]-2-(4-fluorophenyl)-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino) carbonyl]-1H-pyrrole-1-heptanoic acid (Figure 1). It is a member of the drug class known as statins, used for lowering blood cholesterol [1]. It also stabilizes plaque and prevents strokes through anti-inflammation and other mechanisms. It inhibits HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase, an enzyme found in liver tissue that plays a key role in production of cholesterol in the body. Inhibition of this enzyme stops the reduction of HMG-CoA to mevalonate, which is the rate-limiting step in hepatic cholesterol biosynthesis. Inhibition of the enzyme decreases cholesterol synthesis and ultimately increases expression of low-density lipoprotein receptors (LDL receptors) on hepatocytes [2, 3]. Figure 1: Structure of (I) atorvastatin, (II) felodipine. Felodipine (FEL) is a 1, 4 dihydropyridine derivative, that is, chemically described as ethyl methyl-1,4-dihydro-2,6-dimethyl-4-(2,3 dichlorophenyl)-3,5-pyridinedicarboxylate. It is a dihydropyridine calcium channel blocker used mainly for the management of hypertension and angina pectoris like the other calcium channel blockers [4]. Literature survey reveals that spectrophotometric and chromatographic methods, and a stability-indicating LC method, have been reported for determination of ATR in pharmaceutical preparations in combination with other drugs [5–13]. Several chromatographic and spectrophotometric methods have been reported for felodipine assay [14–18]. However, most of the analytical methods developed for the