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UV SPECTROPHOTOMETRIC METHOD FOR SIMULTANEOUS DETERMINATION OF TAMSULOSIN AND FINASTERIDE IN COMBINED DOSAGE FORM

E. Keeravani *, D. AshaMadhuri, Veenasri DS, Satish. J

M.Pharm, Pharmaceutical Analysis and QA

School of Pharmacy, Anurag Group of Institutions, Venkatapur (V), Ghatkesar (M),

Rangareddy (D).

INTRODUCTION

Finasteride (FIN) chemically is, N- (1,1-dimethylethyl)–3-oxo-4-aza-5-androst-1-ene- 17- carboxamide , is a type II 5 alpha reductase inhibitor, slowly reduces prostatic volume. Prostate growth and function is influenced by dihydrotestosterone, 5-alpha-reductase enzyme converts testosterone to dihydrotestosterone. Inhibition of 5-alpha reductase results in decreased level of dihydrotestosterone leading to reduction of prostate size.

Tamsulosin (TAM) chemically is, 5- [(2R)-2[[2-(2-Ethoxy Phenoxy) ethyl] amino] Propyl}- 2- methoxy benzene sulfonamide is a selective alpha 1 adrenoceptor blocking agent. Smooth muscle tone is mediated by the sympathetic nervous stimulation of alpha1 adrenoceptors, which are abundant in the prostate, prostatic capsule, prostatic urethra, and bladder neck. Blockade of these adrenoceptors can cause smooth muscles in the bladder, neck and prostate to relax, resulting in an improvement in urine flow rate and reduction in symptoms of benign prostatic hyperplasia (BPH).

1. Finasteride

2. Tamsulosin

According to the literature survey it was found that few analytical methods such as Visible, UV, polarographic analysis, HPLC methods were reported for finasteride and tamsulosin. The objective of this study was to develop and validate a simple and specific UV spectrophotometric method for the simultaneous determination of finasteride and tamsulosin in formulation. This method exhibited a precise, accurate and cost effective assay for these drugs in mixture.

MATERIALS AND METHODS

Chemicals: 0.1N Hcl, 0.1N NaOH, Water, Acetonitrile, Methanol.

Drugs: Tamsulosin and Finasteride pure powder were gift samples supplied from Intaas Pharmaceutical Ltd, India. Formulation, Urimax F (0.4mg TAM + 5mg FIN per capsule), manufactured by Cipla Pharmaceutical Ltd, India, was purchased from the local pharmacy in Hyderabad, India.Instrument: Shimadzu UV–Visible spectrophotometer (model uv-1800).

Method Selection of solvent andwavelength (λ max): The absorbance of the both drugs i.e TAM and FIN was found maximum in methanol solvent compared to other solvents and the lamba (λ) max of tamsulosin and finasteride was fixed as 225nm and 235nm respectively.

Spectrum of Tamsulosin showing selected wavelength

Spectrum of Finasteride showing selected wavelength

Preparation of FIN Stock Solution: Standard finasteride stock solution was prepared by dissolving 125 mg of drug in 100ml of methanol to get a concentration of 1250 μg ml-1.

Preparation of TAM stock solution: Standard tamsulosin stock solution was prepared by dissolving 10mg of drug in 100ml of methanol to get a concentration of 100 μg ml-1.

Application of Vierodt’s Method: In quantitative estimation of two components by Vierodt’s (Simultaneous equation) method two wavelengths i.e, 225nm of TAM and 235nm of FIN were selected as their respective λ max from the overlain spectrum, at which both drugs have maximum absorbance. A set of two simultaneous equations were formed using absorptivity coefficients at selected wavelengths. The concentrations of two drugs in the mixture were calculated using the following two simultaneous equations.

Cx = A2 ay1 − A1 ay2/ ax2 ay1 − ax1 ay2 --- (1)

Cy = A1 ax2 – A2 ax1/ ax2 ay1 – ax1 ay2 --- (2)

Where, Cx and Cy are the concentrations of x and y

A1 is the absorbance of mixture at λ1, A2 is the absorbance of mixture at λ2 ,ax1 is the absorptive value of x at λ1, ax2 is the absorptive value of x at λ2 ,ay1 is the absorptive value of y at λ1 ,ay2 is the absorptive value of y at λ2.

Preparation of Test Solutions and Estimation of Finasteride and Tamsulosin in formulation

For analysis of commercial formulations, 20 capsules (Urimax F containing 0.4mg TAM and 5mg FIN) were weighed, powdered and weight equivalent to 12.5 mg of finsateride and 1mg of tamsulosin was taken and transferred into a volumetric flask and made up to 100ml with methanol, sonicated for 5min, filtered and further diluted with methanol to get the concentrations within the linearity range of respective drugs and measured the absorbance’s at 235 nm for finsateride and 225 nm for tamsulosin respectively.

RESULTS AND DISCUSSION

The analytical method was validated with respect to parameters such as linearity, precision, accuracy, limit of detection (LOD), limit of quantitation (LOQ) and ruggedness.

Linearity

To construct Beer’s law plot for finasteride and tamsulosin different aliquots of finasteride (1-

8ml) with different concentrations (12.5, 25, 37.5, 50, 62.5, 75, 87.5 and 100 μg ml-1) and tamsulosin (0.1-1ml) with different concentrations (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10μg ml-1) , were prepared by serial dilutions with methanol from the individual stock solutions. Then absorbance of the solutions was measured at 235 nm for finasteride and 225 nm for tamsulosin respectively.

Table 1. Linearity

Parameters

Tamsulosin

Finasteride

Concentration range (μg

1 – 10

12.5 - 100

ml-1)

 

 

Slope

0.059

0.006

Intercept

0.003

0.007

Correlation coefficient (r2)

0.9992

0.9994

Figure 5.Overlay spectra of standard tamsulosin (1-10 μg/ml)

Figure 6.Overlay spectra of standard finasteride drug (12.5-100 μg/ml)

Recovery studies

The recovery studies were carried out at three different levels i.e. 80%, 100% and 120% level. To ensure the reliability of the above method, recovery studies were carried out by mixing a known quantity of standard drug with the pre analysed sample formulation and the contents were reanalyzed by the proposed method. The percent recovery values were in between 98.0-99.8%, which indicates that the method is accurate and reveals that commonly used excipients and additives present in the pharmaceutical formulations did not interfere in the proposed method.

Table 2. Recovery studies

Drug

Amount added (μg

Amount recovered

% Recovery

 

ml-1)

(μg ml-1)

 

Finasteride

12.5

12.46

99.70

10

9.78

98.68

 

15

14.89

99.73

 

Tamsulosin

1

0.981

98.14

0.8

0.789

99.40

 

1.2

1.19

99.60

 

Precision The precision of the method was established by carrying out the analysis of the analytes (n = 6) using the proposed developed method. The low value of standard deviation showed that the methods were precise.

Table 3. Precision studies

Drug

Concentration

Intra-day conc.

 

Inter-day conc. Measured

 

(μg ml-1)

Measured

 

 

 

Mean(μg ml-1)

% *RSD

Mean(μg ml-1)

%*RSD

Mean(μg ml-1)

%*RSD

Finasteride

25

25.05

0.841

25.08

1.106

 

 

 

 

 

 

Tamsulosin

2

2.03

0.674

2.05

0.965

 

 

 

 

 

 

*mean of six observations, Relative standard deviation (RSD)

LOD and LOQ The LOQ of tamsulosin and finasteride was found to be 1μg ml-1 and 12.5μg ml-1 respectively and the LOD was found to be 0.3μg ml-1 and 4μg ml-1 respectively.

Ruggedness The ruggedness test of analytical assay method is defined as degree of reproducibility of assay results obtained by the successful applications of assay over different time, day and among multiple analysts. The % RSD values for assays performed in the same laboratory by two analysts were found to be less than 2, indicating the ruggedness of the method.

Assay Then the amount of drug present in formulations was calculated using the simultaneous equation.

Table 4. Analysis of formulation

Drug name

Amount

Amount

% Label claim

% deviation

 

labeled (mg

estimated (mg

 

 

 

ml-1)

ml-1)

 

 

Finasteride

5mg

4.94

98.8

(-) 1.2

Tamsulosin

0.4mg

0.396

99.0

(-) 1.0

Figure 7. Spectrum of formulation (tamsulosin 2 μg ml-1 and finasteride 25 μg ml-1)

CONCLUSION

A convenient and rapid UV method has been developed for simultaneous estimation of finasteride and tamsulosin in available dosage form. The assay provides a linear response across a wide range of concentrations. Low intra-day and interday % RSD coupled with excellent recoveries. Hence, this method can be easily and conveniently adopted for routine analysis of Finasteride and Tamsulosin in pure form and its dosage forms.

REFERENCES

1.Budavari S. The Merck index.12th edition. White house station, NJ: Merck & co 1994:9138.

2.Sweetman SC. Martindale. The Complete Drug Reference. London: Pharmaceutical Press 2002:2188-2197.

3.Ichioka K, Ohara H, Terada N, Matsui Y, Koji Y, Terai A et al. Long-term treatment outcome of tamsulosin for benign prostatic hyperplasia. Int J Urology 2004; 11(10):870.