Simultaneous Estimation of Metoprolol and Amlodipine from Tablet Dosage Form

 

Sohan S. Chitlange*1, Md. Imran1, Sagar B. Wankhede1 and Dinesh M. Sakarkar2

1Pad. Dr. D. Y. Patil Institute of Pharmaceutical Sciences and Research, Pimpri, Pune-411 018.

2S. N. Institute of Pharmacy, Pusad Dist Yawatmol.

*Corresponding Author E-mail:  sohanchitlange@rediffmail.com

 

ABSTRACT

Simple spectrophotometric methods have been developed for simultaneous estimation of Metoprolol (MET) and Amlodipine (AMD) in two component tablet formulation. The methods employed are Absorbance corrected for interference method and Area under curve method. For Absorbance corrected for interference method the working wavelengths selected are 224 nm for MET and 362.5 nm for AMD. Similarly for Area under curve method the working wavelength ranges selected are 234-242 nm (λ1 – λ2) for AMD and  218-228 nm (λ3 – λ4) for MET. For both the methods linearity was observed in the concentration range of 10-50 mg/ml for MET and 4-20 mg/ml for AMD. The recovery studies confirmed the accuracy of proposed method and the methods were validated as per ICH guidelines.

 

KEY WORDS Metoprolol; Amlodipine; Absorbance corrected for interference; Area under curve

 


INTRODUCTION:

Metoprolol (MET) is Beta blocker, which is official in I.P.1, Chemically it is 1-[4-(2-methoxyethyl) phenoxy]-3-[(1-methylethyl) amino]-2-propanol.2,3. Literature reveals RP-LC4, U.V. spectrosctroscopy5, have been reported for the estimation of metoprolol. Amlodipine (AMD) is chemically a 2-[(2-Aminoethoxy) methyl]-4-(2-chlorophenyl)-1,4-dihydro-6-methyl-3,5-pyridine dicarboxylic acid- 3-ethyl 5-methyl ester and it belongs to the class of calcium channel blocker.2,3. Several spectroscopic6,7, RP-HPLC8,9, HPTLC10, LC-MS/MS11 and LC-MS12 have been reported for the estimation of amlodipine individually and in combination with other drugs. But no method is developed so far for the combination of MET and AMD. A successful attempt is made to estimate the two drugs simultaneously by spectrophotometric analysis. This paper describes simple, rapid, accurate, reproducible and economical method for the simultaneous determination of MET and AMD in tablet formulations using absorbance corrected for interference method and area under curve method.

MATERIAL AND METHODS:

Instrument:

A dual beam Shimadzu UV-visible spectrophotometer 1700 was used in the study.

 

Reagents and chemicals:

Methanol of analytical grade was used as solvent. MET and AMD are obtained as gift samples from Cipla Ltd., Kurkumbh and Glenmark Pharmaceuticals Limited, Nashik, respectively. Marketed formulation Supermet*AM (Nicholas Piramal) of combined dosage form of MET-47.5mg and AMD-5mg were procured from the local market.

 

Method I: Absorbance corrected for interference method13 :

If the identity, concentration and absorpitivity of the one of the absorbing component are known, it is possible to calculate their contribution to the total absorbance of a mixture. The concentration of other absorbing component is then calculated from the corrected absorbance (total absorbance minus the absorbance of the one of the component) in the usual way.

 

ig. 1: Overlain spectra of MET and AMD

Solutions of 20 mg ml of MET and AMD were prepared separately in methanol. Both the solutions were scanned in the spectrum mode from 400 nm to 200 nm. The wavelengths 224 nm and 362.5 nm for MET and AMD were selected respectively (Fig. 1) where both drugs shows linearity in the concentration ranges of 10-50 µg/ml and 4-20 µg/ml with regression coefficient (r2) values 0.9992 and 0.9984 for MET  and AMD and respectively.  The absorbances were taken at 224 nm and 362.5 nm for both the drugs. The absorpitivity (A1%, 1cm) values for MET was 337 at 224 nm and 0 at 360 nm and for AMD was 314 at 224 nm and 134 at 362.5 nm. Mixed standard solutions of the two drugs were prepared in the ratio 47.5:5 µg/ml of MET and AMD respectively using methanol and their absorbances were measured at the selected wavelengths. And the concentrations of the two drugs in mixed standars and the sample solution were calculated.

Fig. 2: Overlain spectra of MET and AMD with Area under the curve ranges.

Method II: Area under curve method:

Standard stock solutions (100 µg/ml) of both MET and AMD were prepared by dissolving separately 10 mg of each drug in methanol and making up the volume upto 100 ml with methanol.

For  area under curve method , the sampling wavelength ranges selected for estimation of AMD and MET are 234-242 nm (λ1 – λ2 ) and  218-228 nm (λ3 – λ4) where both drugs shows linearity in the concentration ranges of 4-20 µg/ml and 10-50 µg/ml with regression coefficient (r2) values 0.9996 and 0.9951 for AMD and MET respectively. The ‘X’ values of the drugs were determined at the selected AUC range.

The ‘X’ value is the ratio of area under curve at selected wavelength ranges with the concentration of component in g/lit. Mixed standard solutions of the two drugs were prepared in the ratio 47.5:5 µg/ml of MET and AMD respectively using methanol and their areas under the curve were measured at the selected wavelength ranges.  The concentrations of the two

 

drugs in mixed standards and the sample solution were calculated using equations (1) and (2).

A1 = 9.924 CAMD  + 312.26 CMET  ..............(1)at 234-242 nm

A2 = 302.39 CAMD + 362.62 CMET  .…........(2) at 218-228 nm

 

Where – 9.924 and 302.39 are ‘X’ values of AMD at λ1- λ2 and λ3 – λ4 respectively. 312.26 and 362.62 are ‘X’ values of MET at λ1- λ2 and λ3 – λ4 respectively.A1 and A2 are the area under curve of mixed standard at λ1- λ2 and λ3 – λ4 respectively. CAMD and CMET are concentrations in gm/l.  Fig. 2 represents the overlain spectra of AMD and MET in the area under curve.        

Both the methods were employed for the analysis of formulations containing the two drugs. The developed methods were validated for repeatability, intermediate precision (inter-day and intra-day precision studies). The accuracy of the proposed methods was determined by performing recovery studies at 80%, 100% and 120% of the test concentration as per ICH guidelines.

RESULT AND DISCUSSION:

The mean % content and mean % recoveries by absorbance corrected for interference and area under curve methods are given in Table 1. For absorbance corrected for interference method the regression equation was Y = 0.0335x + 0.0043 (r2 = 0.9992) in the concentration range of 10-50 µg/ml for MET and Y = 0.0298x + 0.011 (r2 = 0.9978) in the concentration range of 4-20 µg/ml for AMD. Similarly for area under curve method the regression equation was Y = 0.1547x - 0.1239 (r2 = 0.9951) in the concentration range of 10-50 µg/ml for MET and Y = 0.024x + 0.0048 (r2 = 0.9996) in the concentration range of 4-20 µg/ml for AMD. The methods were validated interms of linearity, accuracy, repeatability, inter-day and intra-day precision. The validation data are given in Table 2.

 

CONCLUSION:

The standard deviation, %RSD and standard error calculated for both the methods are low, indicating high degree of precision of the methods. The %RSD is also less than 2% as required by ICH guidelines. The results of the recovery studies performed at three levels (80, 100 and 120 % of the test concentration as per ICH guidelines) shows the high degree of accuracy of the proposed methods. Hence the developed methods are simple, rapid, precise, accurate and can be employed for the routine estimation of Metoprolol and Amlodipine in both bulk and tablet dosage form.

ACKNOWLEDGEMENT:

Authors are thankful to Dr. Avinash D. Deshpande, Director of Pharmacy, Pad. Dr. D.Y.Patil Institute of Pharmaceutical Sciences and Research, Pimpri, Pune for providing necessary facilities and to Cipla Ltd., Kurkumbh for providing the gift sample of Metoprolol and Glenmark Pharmaceuticals Ltd. Nashik for the gift sample of Amlodipine.

 


TABLE 1: RESULTS OF MARKETED FORMULATION ANALYSIS AND RECOVERY STUDIES OF MET AND AMD IN TABLETS

Drug

 

Label Claim

(mg/tablet)

Absorbance corrected for interference method

Area under curve method

% of Label Claim ± S.D*

%RSD*

%Mean Recovery*

% of Label Claim ± S.D*

%RSD*

%Mean Recovery*

MET

47.5

100.25±0.4212

0.4201

101.12

100.23±0.6954

0.6938

99.65

AMD

5

100.46±0.7967

0.7930

100.38

101.1±0.7563

0.7480

100.24

* Denotes average of six determinations.

TABLE 2: VALIDATION DATA OF METOPROLOL AND AMLODIPINE

Parameters

Absorbance corrected for interference method

Area under curve method

MET

AMD

MET

AMD

Repeatability*

%Mean± S.D.

%RSD

Intraday*

%Mean± S.D

%RSD

Interday*

%Mean± S.D

%RSD

 

101.6±0.109

0.1078

 

101.67±0.132

0.1298

 

100.97±0.996

0.9864

 

100.1±0.109

0.1088

 

100.06±0.055

0.5496

 

99.74±0.589

0.5905

 

100.01±0.733

0.7329

 

99.9±0.99

0.9909

 

100.26±0.416

0.4149

 

100.36±0.322

0.3208

 

99.97±0.1380

0.1380

 

101.1±0.098

0.9693

* Denotes average of six determinations.


 

 

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Received on 08.0.2008                                 Modified on 04.04.2008

Accepted on 10.04.2008                            © RJPT All right reserved

Research J. Pharm. and Tech. 1(2): April-June. 2008Page 80-82