INTRODUCTION:

Metoprolol Succinate, (MT) is chemically a bis [(2 RS)-1-[4-(2-methoxyethyl) phenoxy]-3-[(1-methylethyl) amino] propane-2-ol] (2R, 3R)-2,3-dihydroxybutanedioate. It is a prototype β1-antiadrenergic drug which has the potency to increase the heart rate and decrease renin release from kidney¹. It is used in hypotension². Literature survey revealed that Flourimetric, HPLC, LC/MS, GC/MS, methods for estimation of MT individually and in combination with other drugs. A RP-HPLC method of analysis was reported for simultaneous estimation of MT in tablet formulation, since the reported RP-HPLC and LC/MS method is expensive and involves complicated sample preparation, the present work was undertaken for simultaneous estimation of MT in tablet formulations by UV spectrophotometric method³.

MATERIALS AND METHODS:

A double-beam Shimadzu UV- Visible spectrophotometer (Model 1800), with spectral bandwidth of 2 nm, wavelength accuracy ± 0.5 nm and a pair of 1-cm matched quartz cells was used to measure absorbance of the resulting solution. Analytical grade solvents were used in the present study. A drug sample of metoprolol succinate (MT) was procured from M/s Aarti Drugs Pvt. Ltd, Mumbai. Commercial tablets of metoprolol succinate were purchased from the local market.

Determination of linearity range:

MT was accurately weighed (100mg) and dissolved separately in 35 ml of methanol and the volume made up of 100 ml with water in a 100 ml volumetric flask.

One milliliter of the above solutions was diluted separately to 10 ml with methanol in volumetric flask to give 100 μg/ml working standard solutions. These working standard solutions were further diluted for 10μg/ml. These dilutions were scanned in the UV region. MT showed absorption maximum at 222 nm⁴. The overlain spectrum for the above drug is represented in Fig.1.

MT showed linearity range from 2-16 μg/ml at the selected wavelength. From the prepared dilutions a standard curve is plotted by determining the concentration using 222 nm wavelength⁵ (Fig.2).

Analysis of metoprolol succinate:

Commercial formulations, MT-I and MT-II was purchased from a local pharmacy. Twenty tablets of each brand containing 25 mg of MT were weighed and finely powdered in a mortar. A quantity of powder equivalent to 100 mg of MT was weighed accurately and dissolved in 10 ml of methanol and made up to 100 ml in a volumetric flask with water (1000 μg/ml). The solution was then filtered through Whatman filter paper to get a clear solution^6,7. From this 1 ml of solution was drawn and make up to 10 ml with water. The formulation was estimated in one concentration range by diluting stock solutions to 16 μg/ml of MT. The method was validated according to ICH guidelines.

Recovery Studies:

Recovery studies were carried out at three different levels by adding 2.0, 4.0, 6.0 mg/ml of pure drug solution to different samples of tablet powder solution containing the equivalent 100 mg/ml of drug. From the amount of drug found, percentage recovery was calculated^8,9.

Fig.1: Overlain spectrum for the Metoprolol Succinate

Table-1: Optical Characteristics and Precision data of Metoprolol Succinate

Parameters	Value
Equation	y = 0.033x - 0.003
λ_max	222
Beer’s law limit	2-16 μg/ml
Molar absorptivity (lit/mol.cm)	3.67 x 10⁴
Sandell’s sensitivity (μg/cm²/0.001 abs. unit)	1.024 x 10^-2
Correlation coefficient (r²)	0.998
Intercept	0.003
Slope	0.033

Fig.2: Standard Curve of Metoprolol Succinate

Table-2: Determination of Metoprolol Succinate in Pharmaceutical Preparations

Tablet Code	Label Claim (mg/tab)	Amount found (mg)	% Recovery ± SD
MT-I	25	24.83	99.35± 0.25
MT-II	25	24.87	99.48± 0.14

RESULTS AND DISCUSSION:

The proposed method for determination of MT showed molar absorptivity 3.67 x 10⁴l/mol.cm. Linear regression of absorbance on concentration gave the equation y = 0.033x - 0.003 with a correlation (r²) of 0.998 (Table-1).

Relative standard deviation of 0.0829 % and 0.1542 was observed for analysis of five replicate samples of two brands MT-I and MT-II, respectively. Metoprolol Succinate exhibited maximum absorption at 222 nm and obeyed Beer’s law in the range of 2-16 μg/ml. The percentage recovery value between 99.35% and 99.48% (Table-2) indicates that there is no interaction of the excipients present in the formulations. The study was made to test ruggedness of the method through an interday and intraday analysis of samples.

CONCLUSIONS:

Based on the results obtained, it is found that the proposed method of analysis is accurate, precise, reproducible and economical and can be employed for routine quality control of Metoprolol Succinate in tablet formulations.

ACKNOWLEDGEMENT:

The authors are pleased to express their gratitude to Dr. R. M. Dubey, Managing Director, IFTM for providing necessary facilities to carry out this work.

REFERENCES:

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2. Bush ES and Mayer, Goodman and Gilman’s: The Pharmacological Basis of Therapeutics, McGraw Hill Publications, London, 9^th edition, 1996; 133.

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Received on 15.09.2010 Modified on 24.09.2010

Research J. Pharm. and Tech. 4(2): February 2011; Page 271-272