INTRODUCTION:

Simvastatin(SIM) is chemically 2,2-Dimethyl butanoic acid, 1,2,3,7,8a-hexahydro-3,7-dimethyl-8-[2-(tetrahydro-4-hydroxy-6-oxo-2-pyran-2-yl)-ethyl]-1-naphthalenyl ester [1], which is a lipid regulating drug, it is a competitive inhibitor of 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG-CoA reductase), the rate determining enzyme for cholesterol synthesis [2]. A detailed survey of literature revealed UV spectrophotometric methods reported for the simultaneous estimation of Simvastatin and Ezetimibe in its tablet dosage forms [3, 4], Simvastatin and Nicotinic acid from tablet dosage form [5]. But no method reported for the estimation of Simvastatin alone in its tablet dosage forms [6]. In the present investigation an attempt was made to develop a simple and precise ultra violet (UV) spectrophotometric method with greater precision, accuracy and sensitivity for the analysis of simvastatin in its pharmaceutical dosage forms.

MATERIALS AND METHODS:

Instruments and Reference standard:

An UV-Visible double beam spectrophotometer –Systronics 2203(smart) with matched quartz cells corresponding to 1cm path length. Sartorious GE 412 single pan electronic balance was used for weighing the materials. Pure samples of Simvastatin were obtained from Seco biotech, Vijayawada, India. Ethanol of analytical grade were purchased from E.Merck(India) Ltd., Mumbai.

Procedure:

Simvastatin 100mg was accurately weighed and dissolved in 100ml of ethanol to get a stock solution of 1000mcg/ml. Aliquots of 1000mcg/ml solution were suitably diluted with ethanol to get a final concentrations of 1-40mcg/ml. The UV spectrophotometric measurement of Simvastatin in ethanol, in the range of 200-400nm showed the λ_maxat 237.8nm (Table I) Absorbance was measured at 237.8nm against ethanol as a blank.

Estimation of Simvastatin in its tablet formulations:

For the estimation of Simvastatin in tablet dosage form, two commercial brands were procured. Twenty tablet contents of each brand were weighed. The tablet powder, equivalent to 100mg of Simvastatin was weighed accurately, transferred to a clean 100mL volumetric flask and dissolved in ethanol and the final volume was made up. The solution was filtered through a Whatmann filter paper No.40. An aliquot corresponding to 10mcg/ml was analyzed. The result of the analysis of the tablet formulations is presented in Table II.

Recovery studies:

Recovery studies were carried out at three different levels by adding 10mg of the standard drug to the following concentrations viz 6, 8,10mcg/ml of preanalysed samples. Each level was repeated five times. Percentage recovery was calculated from the amount of drug found in the solution (Table III).

Repeatability testing:

Repeatability studies were carried out by using three different concentrations of three replicates each. Percentage label claim was calculated from the amount of drug found in the solution. (Table IV).

Table I: Selection of wavelength

S. No.	Wavelength(nm)	Absorbance
1	237.1	0.496
2	237.2	0.499
3	237.3	0.502
4	237.4	0.505
5	237.5	0.507
6	237.6	0.510
7	237.7	0.512
8	237.8	0.514
9	237.9	0.513
10	238.0	0.512

Table II: Analysis of Simvastatin in tablets

Tablet formulation

Lable claim

(mg)

Amount found

(mg/tab)

% Label claim

found ± SD

Brand A

10.07

100.7±0.240

Brand B

20.12

100.58±0.252

*Average of five determinations. SD=Standard Deviation

Table III: Recovery Studies

Concentration of Formulation (mcg/ml)	Concentration of drug added to the Formulation (mg)	Amount recovered (mg/tab)	% Recovery ±SD (% w/w)
6	10	9.90	99.0
8	10	9.91	99.1
10	10	9.85	98.5

Table IV: Repeatability Testing

Concentration of Formulation (mcg/ml)	Amount found (mg/tab)	% Label claim
6	10.12	101.2
8	9.93	99.3
10	10.04	100.4

*Average of three determinations

RESULTS AND DISCUSSION:

The proposed method for the estimation of Simvastatin in tablet formulation was found to be simple, accurate, precise, economical and rapid. Simvastatin exhibited maximum absorption at 237.8nm and obeys Beer’s law in the concentration of 1-40mcg/mL. The brands of formulation shows the percentage purity values ranging from 100.7 to 100.58%. Recovery studies revealed that the values lie between 98.5 to 99.1%. This indicated that there is no interference of the excipients present in the formulations. The repeatability test expresses the precision of the given method.

The developed method was found to be accurate, precise, reproducible and stable, which indicates that this method can be used for the routine analysis of Simvastatin in its solid dosage forms.

ACKNOWLEDGEMENT:

The authors are grateful to Seco Biotech, Vijayavada, India for providing gift sample of Simvastatin. The authors’ are also grateful to P.R.R.M. College of Pharmacy, Kadapa for providing necessary facilities to carry out this work.

REFERENCES:

1. Wilson and Gisvold’s Text book of organic medicinal and pharmaceutical chemistry, 10^th ed, Lippincott Williams and Wilkins: Philadelphia; 1998; 619.

2. Martindale, The complete drug reference, 34^th ed, Pharmaceutical press: Grayslake, USA; 2005; 999.

3. Rajput SJ, Raj HA,; Simultaneous spectroscopic estimation of Ezetimibe and Simvastatin in tablet dosage forms; Indian J. Pharm. Sci., 2007, 69(6), 759-762.

4. http://www.streetdirectory.com/travel_guide/119187/science/spectrophotometric_of_ simvastatin_ _ezetimibe_in_tablet_formulae. html.

5. Bhatia Neela M, Shaha Suhel S, Singhvi I, Jadhav Namdev R, Bhatia Manish S, Spectrophotometric estimation Simvastatin and Nicotinic acid from tablet dosage form; The Indian Pharmacist, 2007; 6; 89-92, 95.

6. http://www.google.co.in/search?hl=enandq=spectrophotometric+estimation+of+simvastatinand meta=andaq=oandoq=