Development and Validation of UV Spectrophotometric Methods for the Estimation of Pravastatin Sodium in Bulk and Tablet Dosage Form.

 

D. B. Doshi1* and P. A. Bhatt2

1APMC College of Pharmaceutical Education and Research, College Campus, Motipura, Himatnagar-383001, Gujarat2L.M. College of Pharmacy, Ahmedabad-380009, Gujarat

*Corresponding Author E-mail: divyesh_81181@yahoo.com

 

ABSTRACT:

Pravastatin sodium (PRS) is a HMG Co A reductase inhibitor, used as a lipid lowering agent. Two simple, sensitive and economical UV spectrophotometric methods have been developed for the estimation of pravastatin sodium in bulk drug and pharmaceutical tablet dosage forms. Methods were based on the first order derivative spectroscopy and area under curve method. Both method obeyed Beer’s law in the concentration range of 10–20 µg/ml. The results obtained with the proposed methods are in good agreement with labeled amounts when tablet dosage forms were analyzed. The proposed methods were validated for analytical method validation parameter as per ICH and US FDA guidance documents. The proposed methods have adequate specificity, sensitivity and reproducibility for quality control assay of pravastatin sodium in bulk and tablet dosage form without any interference from excipients.

 

KEYWORDS: Pravastatin sodium, Derivative spectroscopy, Area under curve method, Analytical method validation.

 


INTRODUCTION:

Pravastatin sodium ((3R,5R)–3,5–dihydroxy–7–[(1S,2S,6S,8S,8aR)–6–hydroxy–2–methyl–8–[[(2S)–2–methylbutanoyl]oxy]–1,2,6,7,8,8a-hexahydronaphthalen–1-yl] heptanoate) (Fig. 1), a competitive inhibitor of HMG Co A reductase, is mainly used in the treatment of atherosclerosis and hypercholestremia1.

 

Literature survey revealed HPLC2–7, LC/MS8-10, capillary electrophoresis11, electrochemical voltammetric method12 and spectrophotometric13,14 methods for estimation of pravastatin sodium in bulk drug, in biological fluids or pharmaceutical formulation. Chromatographic method and mass selective detection method are time consuming and costly and often not available for routine analysis. However, there is no single UV method for estimation of pravastatin sodium is reported till date using derivative spectroscopy and area under curve method for estimation of pravastatin sodium in bulk as well as tablet dosage form. Hence, an attempt has been made to develop new UV method for its estimation in bulk and pharmaceutical formulations with good accuracy, simplicity, precision and economy using derivative spectroscopy and area under curve method..

 

MATERIAL AND METHODS:

Instruments and reagents:

An analytically pure sample of pravastatin sodium was a gifted by Astron Research Ltd., Ahmedabad, Gujarat, India. Distilled water was made by glass distillation assembly and used throughout experiment. A double beam Shimadzu 1700 UV–Visible spectrophotometer having two matched quartz cells with 1cm light path was employed for spectral measurement. Commercially available pravastatin sodium tablets claimed to contain 20 mg of the pravastatin sodium were purchased from the local market.

 

Preparation of standard stock solution:

The pravastatin sodium standard stock solution was prepared by dissolving 100 mg of pravastatin sodium in a 100 ml volumetric flask containing 70 ml of the distilled water, sonicated for about 20 min and then made up to volume with the distilled water. Aliquot 10.0 ml this solution to 50.0 ml volumetric flask and diluted up to mark with distilled water

 

Analysis of marketed formulations:

Twenty tablets were weighed to obtain the average tablet weight, which were then powdered. Table powder equivalent to 100 mg of pravastatin sodium was weighed and transferred to 100 ml volumetric flask containing 70 ml distilled water. This mixture was sonicated for 20 minute to ensure complete solubility of the drug. The volume was made up to mark with the distilled water and filtered through Whatman filter paper No. 41. Aliquot 10 ml filtrate to 50 volumetric flask and diluted up to mark with distilled water. Aliquot 0.8 ml this solution to 10 ml volumetric flask and volume was adjusted to mark with distilled water.

 

Fig 1: Chemical structure of Pravastatin sodium

 

First order derivative spectroscopy method (Method A):

The zero order absorption spectra of standard and sample solutions were recorded in the range of 300–200 nm. The absorption spectra thus obtained were derivatized to first order. First order derivative spectra of pravastatin sodium in distilled water showed a sharp maxima peak at 226.0 nm and sharp minima peak at 251.0 nm (Fig. 2), which were selected for its estimation. The amplitude between maxima and minima wave length means difference of absorbance (dA/dl) at 226.0 nm and 251.0 nm was calculated. The calibration curve for pravastatin sodium was plotted in the concentration range 10–20 µg/ml by plotting the concentrations of pravastatin sodium versus amplitudes. By using the calibration curve, the concentration of the sample solution can be determined.

.

Fig. 2: First order derivative spectrum of pravastatin sodium in distilled water.

 

Area under curve method (AUC) (Method B):

The zero order absorption spectra of standard and sample solutions were recorded in the range of 300–200 nm. The area under curve of pravastatin sodium in the range of 243.0–233.0 nm was calculated by inbuilt software. The calibration curve for pravastatin sodium was plotted in the concentration range 10–20 µg/ml by plotting the concentrations of pravastatin sodium versus area under curve of pravastatin sodium. By using the calibration curve, the concentration of the sample solution can be determined.

 

Fig. 3: Zero order spectrum of pravastatin sodium in distilled water.

 

RESULTS AND DISCUSSION:

The goal of the present study was to develop a rapid, precise, accurate and economic UV spectrophotometer methods for the analysis of pravastatin sodium in bulk and its pharmaceutical tablet formulations and validate develop method as per US FDA guideline14 and ICH guideline15. The validation parameters were summarized in Table 1. As the drug pravastatin sodium showed a broad spectrum, the derivative spectroscopy method applied has the advantage that it locates the hidden peak in the normal spectrum when the spectrum is not sharp and it also eliminate the interference caused by the excipients and the degradation products present, if any, in the formulation. The first order derivative spectrum showed sharp maxima peak at 226.0 nm and sharp minima peak at 251.0 nm when N=4. The AUC (Area under curve) method involves the calculation of integrated value of absorbance with respect to the wavelength between two selected wavelengths. Area calculation processing item calculates the area bound by the curve and the horizontal axis. The wavelength range (243.0–233.0 nm) is selected on the basis of repeated observations so as to get the linearity between area under curve and concentration. Both the method showed good linear relationship in the concentration range of 10–20 µg/ml. The correlation coefficient was found to be 0.9999 and 0.9997, respectively for method A and method B. The regression equation was found as y = 0.0051x - 0.0104 and y = 0.4496 + 0.0345, respectively for method A and Method B. The calculated LOD and LOQ values were found to be 1.04 µg/ml and 3.14 µg/ml for Method A and 0.67 µg/ml and 2.04 µg/ml for method B. These methods were validated for intra–day and inter-day precision. The relative standard deviation (RSD) for intra-day and inter-day precision were found to be 0.99–1.23% and 1.13–1.43% for method A while 0.30–0.88% and 0.51–1.14% for Method B, respectively indicating good precision. Repeatability was found to be 0.71% and 0.32% for method A and method B, respectively. To examine the accuracy of the developed method, recovery studies were carried out three different concentration levels in triplicate by spiking standard pravastatin sodium solution in commonly used tablet excipients and the results obtained are given in Table 2

 


Table 1:    Summary of validation parameter

No.

Parameter

First order derivative spectroscopy method

Area under curve method

1

Linearity range

10-20 µg/ml

10-20 µg/ml

2

Correlation Co-efficient

0.9999

0.9997

3

Regression equation (y=mx + c)

y = 0.0051x - 0.0104

y = 0.4496 + 0.0345

4

Precision (% RSD)

Intra day

Inter day

 

0.99% - 1.23%

1.13% - 1.43%

 

0.30% - 0.88 %

0.51% - 1.14 %

5

% Mean recovery

99.2% -100.1%

99.7% -101.1 %

6

Limit Of Detection

1.04 µg/ml

0.67 µg/ml

7

Limit Of Quantification

3.14 µg/ml

2.04 µg/ml

 

Table 2:    Recovery study of pravastatin sodium

Level

Amount of spike PRS (mg/ml)

First order derivative spectroscopy method

AUC method

Amount of PRS found

% Recovery (n=3)

Amount of PRS found  (mg/ml)

% Recovery (n=3)

75%

12

11.91 ± 0.1132

99.2 ± 0.9434

11.97 ± 0.0442

99.7 ± 0.3682

100%

16

15.96 ± 0.1961

99.8 ± 1.2255

16.04 ± 0.0539

100.3 ± 0.3371

125%

20

20.01 ± 0.1132

100.1 ± 0.5660

20.23 ± 0.1515

101.1 ± 0.7574

 

Table 3:    Estimation of pravastatin sodium in tablet dosage form by the proposed method(s).

Brand

No.

Label claimed (mg/tablet)

First order derivative spectroscopy method

Area under curve method

Amount found (mg/tablet) Mean ± S.D. (n = 3)

% Assay Mean ± S.D (n=3)

Amount found (mg/tablet) Mean ± S.D. (n = 3)

% Assay

Mean ± S.D (n=3)

1

20

20.03 ± 0.14

100.2  ± 0.71

19.96 ± 0.07

99.8  ± 0.36

2

20

20.20 ± 0.25

101.0 ± 1.23

20.07 ± 0.08

100.4 ± 0.39

 


The mean percent recoveries obtained as 99.2–100.1% and 99.7–101.1% for method A and method B, respectively indicate good accuracy of the method. The proposed method was successfully applied for the analysis of two marketed tablet formulation of pravastatin sodium (20 mg/tablet) and the results obtained are given in Table 3. The average drug content was found to be 100.2% and 101.0% by method A and 99.8% and 100.4% by method B.

 

CONCLUSION:

The results of the study showed that the proposed UV spectrophotometric methods are simple, rapid, precise, accurate, specific and sensitive for determination of pravastatin sodium, without any interference from the excipients. Hence, this method is suitable for routine analysis of pravastatin sodium in bulk and its tablets dosage form.

 

ACKNOWLEDGEMENT:

The authors are thankful to M/s Astron Research Ltd., Ahmedabad, Gujarat, India for providing gift samples of pravastatin sodium.

 

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Received on 23.02.2010       Modified on 20.03.2010

Accepted on 07.04.2010      © RJPT All right reserved

Research J. Pharm. and Tech.3 (3): July-Sept. 2010; Page 869-871