DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC METHOD FOR SIMULTANEOUS ESTIMATION OF OLMESARTAN MEDOXOMIL AND CILNIDIPINE BY SIMULTANEOUS EQUATION METHOD

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About Authors:
Nehal C. Ghelani*, Krutika Bhalodiya, Ketan Dadhania, Shital Faldu
Department of Quality Assurance
Smt. R. D. Gardi B. Pharmacy College, Rajkot, Gujarat, India
*nehalghelani10@gmail.com

Abstract
UV Spectrophotometric method has been developed for simultaneous estimation of Olmesartan Medoxomil (OLME) and Cilnidipine (CILNI) in bulk drug and in laboratory mixture. This method utilizes methanol as a solvent and λmax of Olmesartan Medoxomil and Cilnidipine selected for analysis was found to be 241 nm and 253 nm respectively. Linearity was observed in the Olmesartan Medoxomil concentration range of 4-20μg/ml and Cilnidipine concentration range 2 -10 ug/ml (r2 = 0.998 and r2 0.999) of both drugs. The accuracy and precision were determined and found to comply with ICH guidelines. This method showed good reproducibility and recovery with % RSD in the desired range. The proposed methods can be successfully applied for the routine analysis of both the drugs. This method was simple, rapid, accurate, and sensitive.

REFERENCE ID: PHARMATUTOR-ART-2177

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 6

Received On: 04/04/2014; Accepted On: 09/04/2014; Published On: 01/06/2014

How to cite this article: NC Ghelani, K Bhalodiya, K Dadhania, S Faldu; Development and Validation of Spectrophotometric Method for Simultaneous Estimation of Olmesartan Medoxomil and Cilnidipine by Simultaneous Equation Method; PharmaTutor; 2014; 2(6); 160-166

INTRODUCTION
Olmesartan Medoxomil (OLME) (fig. 1a) is the chemically known as, 2,3-dihydroxy-2-butenyl4(1-hydroxy-1-methylethyl)-2-propyl-1-[p-(o-1H-tetrazol-ylphenyl)benzyl]imidazole carboxylate, cyclic 2,3-carbonate. Olmesartan is a prodrug that works by blocking the binding of angiotensin II to the AT1 receptors in vascular muscle; it is therefore independent of angiotensin II synthesis pathways, unlike ACE inhibitors. By blocking the binding rather than the synthesis of angiotensin II, olmesartan inhibits the negative regulatory feedback on renin secretion. As a result of this blockage, olmesartan reduces vasoconstriction and the secretion of aldosterone[1-3]. Cilnidipine(CILNE) (fig. 1b)  the chemically known as, o3-(2-methoxyethyl) O5-[(E)-3-phenylprop-2-enyl]2,6-dimethyl-4-(3-nitrophenyl)-1,4dihydropyridine-3,5-dicarboxylate. Cilnidpiine is it reduces the incidense of pedal edema unlike amlodipine. Cilnidipine due to its blocking action at N-type calcium channel dilates both arteriole & venules as a result the pressure in the capillary bed is reduces. The accumulated fluid in the tissues flows back to veins & thus Cilnidipine minimizes the incidence of pedal edema[1-4]. Combination drug products of OLME and CILNI are widely marketed and used in the treatment of hypertension[5-7]. Several analytical methods like UV spectrophotometry, HPLC, HPTLC, UPLC have been reported for estimation of OLME & CILNI by single drug and also by combining with other drugs. However no methodhas been reported till date for the simultaneous estimation of OLME & CILNI using the UV spectrophotometric method. The present paper describes the development and validation of two analytical methods for simultaneous estimation of OLME & CILNI by UV spectrophotometry in tablet dosage form; the methods include simultaneous equation method & absorbance ratio method.[8-12] The proposed methods are optimized and validated as per the ICH guidelines [13-14].


Fig. 1 Chemical structures of the analytes (1a) OLME & (1b) CILNI

MATERIALS AND METHODS

Instrumentation
Double  beam  UV-visible  spectrophotometer (heλios Alpha, Model - V 7.09)    having  two  matched  quartz  cells  with  1  cm  light  path. An Electronic analytical balance (Contech, CA34 Model) was used in the study.

Material and reagent:
Double distilled water and Whatmann filter paper (0.45μm) were used for filtration. Active pharmaceutical ingredient (API) working standards of Olmesartan medoxomil (OLME),  was obtained as gift sample from Intas Pharma limited, Ahemdabad, Indaa and Cilnidipine(CILNI) was obtained as gift sample from J. B. Chemicals, Surat, Gujarat, India and test samples (tablets with composition OLME-40 mg and CILNI – 10mg ) were procured from the local market.

Preparation of Standard Stock solution of OLME and CILNI:
Accurately weighed quantity of Olmesartan medoxomil 25 mg was transferred to 25 ml volumetric flask, dissolved in 10 ml of methanol and diluted up to mark with methanol to give a stock solution having strength of 1mg/ml.

Preparation of Working Standard Solution of OLME and CILNI:
100 µg/ml of OLME and CILNI solution were prepared by diluting 10 ml of stock solution to 100 ml with methanol in separate 100 ml volumetric flask. Suitable aliquots of this solution were diluted up to the mark with methanol to get the concentration range of 7,9,11,13,15 μg/ml for OLME and 3,4,5,6,7 μg/ml for CILNI.

(A) Preparation of Working Standard Solution OLME
100 mg/ml of OLME solution was prepared by diluting 1 ml of stock solution with methanol in 10 mlvolumetric flask up to the mark.

(B) Preparation of Standard Solution of Cilnidipine 

Preparation of Standard Stock Solution of CILNI
Accurately weighed quantity of Cilnidipine 25 mg was transferred to 25 ml volumetric  flask and make up to methanol and sonicate for 30 min for dissolving drug, to give a stock solution having strength of 1mg/ml.

Preparation of Working Standard Solution CILNI
100 mg/ml of CILNI solution was prepared by diluting 2.5 ml of stock solution with methanol in 25 ml volumetric flask up to the mark.

Procedure for Determination of Wavelength for Measurement
1.0 ml of working standard stock solution of OLME (100 mg/ml) and 1.0 ml of working standard stock solution of CILNI (100 mg/ml) were pipette out into two separate 10 ml volumetric flask and volume was adjusted to the mark with methanol to get 9mg/ml of OLME and 6 mg/ml of CILNI. Each solution was scanned between 200 - 400 nm against methanol as a reagent blank. Wavelengths were selected from the overlay spectra of OLME and CILNI.

Preparation of Calibration Curve

(A)Calibration Curve for OLME
Calibration curve for OLME consists of different concentrations of standard OLME solution  ranging from 4-20 mg/ml. The solutions were prepared by pipetting out 0.7, 0.9, 1.1, 1.3, and 1.5 ml of the working standard solution of OLME (100 mg/ml) into series of 10 ml volumetric flasks and the volume was adjusted to mark with methanol. The absorbance of the solutions was measured at 253 nm and 241 nm against methanol as a reagent blank. Calibration curve was plotted at both wavelengths and two equations were formed using the specific absorbance (absorptivity).

(B) Calibration Curve for CILNI
Calibration curve for CILI consisted of different concentrations of standard CILNI solution ranging from 1-10 mg/ml. The solutions were prepared by pipetting out 0.3, 0.4, 0.5, 0.6 and 0.7 ml of the working standard solution of CILNI (100 mg/ml) into series of 10 ml volumetric flasks and the volume was adjusted to mark with methanol.

The absorbance of the solutions was measured at 253 nm and 241 nm against methanol as a reagent blank. Calibration curve was plotted at both wavelengths and two equations were formed using the specific absorbance (absorptivity).

Validation of proposed method
Parameters to be considered for the validation of method are:
Linearity and Range

The linearity response was determined by analyzing 5 independent levels of calibrationcurve in the range of 4 - 20 mg/ml and 1-10 mg/ml for OLME and CILNI respectively.

The calibration curve of absorbance vs. respective concentration was plotted and correlation coefficient and regression line equations for OLME and CILNI were calculated.

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