INTRODUCTION:

Telmisartan is an angiotensin II receptor antagonist (ARB) used in the management of hypertension. It selectively antagonizes angiotensin II binding to the AT1 subtype receptors. Inhibition of AT1 receptors leads to vasodilation and inhibits the angiotensin II mediated aldosterone production which in turn leads to decrease in sodium and water excretion and also increases potassium excretion and thereby causes a reduction in blood pressure. Chemically it is 2-(4-{[4-methyl-6-(1-methyl-1H-1,3-benzodiazol-2-propyl-1H-1,3benzodiazol-1-yl] methyl} phenyl) benzoic acid.^1,2

Rosuvastatin Calcium is chemically, (E)-(3R,5S)-7-(4-(4-flurophenyl)-6-isopropyl-2-[(methyl(methanesulfonylamino)] pyrimidine-5-yl)-3,5-dihydroxyhepten-6-oic acid calcium.

Normally statins are HMGCoA reductase inhibitors that are found to be effective in the reduction of total cholesterol and LDL cholesterol and hence it is indicated for dyslipidemias. In addition to it, rosuvastatin also possess pleiotropic effects which include improvement in endothelial function, anti-inflammatory, antithrombotic and anti-oxidant effects.^1,2

Rosuvastatin Calcium and Telmisartan is used as fixed dose combination in the coronary heart disease. This combination contains rosuvastatin 10mg as a lipid lowering agent and Telmisartan 40mg as an antihypertensive agent. Various analytical methods are available for the estimation of Telmisartan and rosuvastatin in combined dosage form as well as individual drugs^3-13. The aim of the present study was to develop a simple UV spectroscopic method which can be used in regular laboratory practices.²

MATERIAL AND METHODS:

Materials:

The pure samples of Rosuvastatin Calcium and Telmisartan were obtained as gift samples from Microlabs. The solvents used were analytical grade Methanol and Phosphate buffer pH 5.5. Marketed product TELROSE was obtained from local market.

Instruments:

The main instruments used were UV-Visible double beam spectrophotometer Shimadzu 1800, IR spectrophotometer Shimadzu, IR affinity-1, pH meter and Electronic balance

Methodology:

Method Development and Optimization²²:

Selection of solvents:

Solvents were selected based on the solubility of Rosuvastatin and Telmisartan. Solubility in various solvents were checked using literatutre review followed by trial and error method. Finally methanol was selected as a solvent for Telmisartan and phosphate buffer pH 5.5 for Rosuvastatin Calcium.^14-22

Selection of wavelength:

10μg/ml solution of Rosuvastatin Calcium and 40μ/ml of Telmisartan were prepared in the selected solvents and ʎmax was observed at 242.8nm and 295.2 respectively.These wavelengths were used for the study.

Fig: 1 Overlay Spectrum Of Rosuvastatin Calcium

Fig:2 Overlay spectrum of Telmisartan

Preparation of standard stock solution:

10mg of rosuvastatin was weighed and dissolved in 10ml of phosphate buffer to yield 1000μg/ml solution. Similarly 10mg of Telmisartan was weighed and dissolved in 10ml of methanol to get 1000μg/ml of standard stock solutions.

Preparation of resolution mixture:

40mg of Telmisartan and 10mg of rosuvastatin were weighed and dissolved in 50ml of phosphate buffer pH 5.5 This solution was filtered and filtrate was used for the analysis of Rosuvastatin Calcium. The residue was dissolved in methanol and used for the determination of Telmisartan^.

Solvent Extraction and Assay using UV-visible spectrophotometry:

20 tablets were accurately weighed, powdered and average weight was calculated. Powder equivalent to 10mg (0.1655g) was weighed and dissolved in 10ml phosphate buffer pH 5.5. This solution was filtered using Whatmann filter paper and filtrate collected contains Rosuvastatin and the residue obtained contains Telmisartan.

Estimation of Rosuvastatin:

The filtrate obtained was diluted with phosphate buffer in a 10ml volumetric flask and five different concentration of 5μg/ml, 10μg/ml, 15μg/ml and 20μg/ml was prepared and measured the absorbance at 243.8nm.

Estimation of Telmisartan:

The residue obtained was used for the estimation of Telmisartan, transferred the residue to a volumetric flask of capacity 10ml and dissolved and final volume was made up using methanol. Five different concentrations of 5μg/ml, 10μg/ml, 15μg/ml and 20μg/ml were prepared and measured the absorbance at 295.2nm.

RESULTS:

The aim of the present study was to develop a simple spectrophotometric method to estimate Telmisartan and Rosuvastatin Calcium in combined dosage form. Solvent extraction procedure was used to separate each components from the combined tablet dosage form.

Optimization of Experimental conditions:

Method: Solvent extraction followed by Assay using UV-Visible spectrophotometer

Solvents: Phosphate buffer pH 5.5 for Rosuvastatin and Methanol for Telmisartan

Wavelength: 242.8nm for Rosuvastatin and 295.2nm for Telmisartan

Validation of developed method²³:

The method was validated according to ICH guidelines for accuracy, precision, linearity, LOD and LOQ as per ICH Q2B Guidelines.

Accuracy:

Accuracy of the developed method was determined by recovery study. Recovery studies were performed at 100% level by standard addition method and percentage recovery were calculated. The absorbance was measured in three replicates and the standard deviation and %relative standard deviation were calculated. The results are presented in Table No1

Table 1: Results of Recovery studies

	Rosuvastatin			Telmisartan
Concentration µg/ml	05	10	15	05	10	15
Amount of Standard Added	05	10	15	05	10	15
Mean % Recovery	102.9	101.9	102.4	98.42	98.48	98.41
SD	0.8219	0.01	0.275	0.3914	0.0424	0.3914
%RSD	0.7984	0.009	0.26	0.3977	0.0430	0.3977

Table 2: Results of Intraday precision Studies

	Rosuvastatin			Telmisartan
Concentration µg/ml	10	15	20	10	15	20
MEAN	0.155	0.385	0.540	0.421	0.646	0.868
SD	0.0005	0.0005	0.0002	0.0008	0.0006	0.0004
%RSD	0.3722	0.14987	0.050371 %	0.194	0.08931	0.0543%

Table 3: Results of inter-day precision Studies

	Rosuvastatin			Telmisartan
Concentration µg/ml	10	15	20	10	15	20
MEAN	0.158	0.386	0.538	0.426	0.647	0.862
SD	0.001	0.0018	0.0008	0.0014	0.0013	0.0005
%RSD	0.63%	0.47%	0.15%	0.33%	0.199%	0.067%

Precision:

The precision was determined using intraday precision studies as well as intermediate precision studies.

Intraday precision or repeatability:

It was carried out by analyzing the sample three times in the same day. Three concentrations were prepared (10μg/ml, 15μg/ml, 20μg/ml) for both the drugs and absorbance were measured. This procedure was repeated thrice in the same day, standard deviation and % relative, standard deviation was calculated.

Inter-day precision or reproducibility:

It was carried out by measuring the absorbance of concentrations 10, 15 and 20µg/ml for three consecutive days. The absorbance was measured at 243.8nm and 295.2nm for rosuvastatin and Telmisartan respectively.

Linearity:

Linearity study was performed to evaluate the linear relationship across the range of analytical method developed and it was established using linear regression equation. It was determined by making a series of five concentrations (5μg/ml, 10μg/ml, 15μg/ml, 20μg/ml, 25μg/ml) of each drug and measured the absorbance of each concentration. Calibration graphs were plotted for each drug by taking concentration on x-axis and absorbance at y-axis. Linearity for each drug is obtained from this graph. The results are presented in Table No 4

Fig 3: Linearity of Rosuvastatin

Fig 4: Linearity of Telmisartan

Limit of detection(LOD) and limit of quantitation (LOQ):

In this study the LOD and LOQ was estimated by using standard deviation of the blank by the equation mentioned below

LOD = 3.3σ/S

LOQ = 10σ/S

The Results are given in the Table No 4

Table 4: Results of Other validation parameters

Method parameters		Rosuvastatin Calcium	Telmisartan
Linearity (µg/ml)	Linearity (µg/ml)	5-25	5-25
	y-intercept	0.2175	0.0585
	slope	0.0316	0.089
	R² value	0.9981	0.9997
LOD and LOQ	MEAN	0.099	0.0178
	SD (σ)	0.0007	0.0006
	LOD	0.0262µg/ml	0.0233µg/ml
	LOQ	0.0794µg/ml	0.0754µg/ml

Assay of Marketed formulation:

For the assay of rosuvastatin and Telmisartan in combined dosage form a resolution mixture was prepared in the same ratio as in tablet (10:40) and using solvent extraction method two components were separated and estimated separately using UV-Visible spectrophotometer. The marketed formulation was also assayed using the same procedure and Percentage label claim was calculated. The results of assay of Marketed formulation are given in Table 5

Table 5: Assay Of Marketed formulation

	Rosuvastatin	Telmisartan
MEAN	98.39%	98.34%
SD	0.0240	0.0452
%RSD	0.0244%	0.0459%

DISCUSSIONS:

A simple Solvent extraction procedure was used to separate each component from the combined tablet dosage form. The solvents selected for the analysis were Methanol and Phosphate buffer pH 5.5 and the lamda max was found to be 242.8nm and 295.2 respectively for rosuvastatin and Telmisartan in these solvents. The selection of the solvent was based on the solubility properties. Both drugs were soluble in methanol but only rosuvastatin was soluble in Phosphate buffer pH 5.5. This solubility pattern of Telmisartan and rosuvastatin aided in selective separation and the drugs were able to analyze individually .In the initial step rosuvastatin was extracted from the combined drug using Phosphate buffer and residue was used for the analysis of Telmisartan. The accuracy of the method was determined by recovery studies using standard addition method and the standard deviation and %relative standard deviation were calculated for 100% level and the %RSD found to be less than 2%.Linearity of the method was found to be 5-25µg/ml for Rosuvastatin and Telmisartan. The R²valueswere found to be 0.9990 for rosuvastatin and 0.9998 for Telmisartan. The method was found precise as the %RSD values were below 2%. The LOD and LOQ values were found to be 0.02622µg/ml and 0.07944µg/ml for rosuvastatin and 0.02327µg/ml and 0.0754µg/ml for Telmisartan respectively which showed the sensitivity of the developed method. The mean %label claims of the marketed formulation was 98.49% and 98.34% for rosuvastatin and Telmisartan respectively.

CONCLUSION:

The results of validation parameters leads to the conclusion that the proposed method was found to be simple, sensitive, accurate, precise and can be successfully employed for the routine analysis of Rosuvastatin Calcium and Telmisartan in laboratories for marketed formulations.

AKNOWLEDGEMENT:

The Authors are thankful to Nirmala college of Pharmacy, Muvattupuzha, Kerala for providing all facilities to carryout the research work. We are also grateful to Microlabs for providing Rosuvastatin Calcium and Telmisartan for as gift samples.

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Received on 29.09.2020 Modified on 22.05.2021

Research J. Pharm. and Tech. 2022; 15(5):2065-2069.

DOI: 10.52711/0974-360X.2022.00341