INTRODUCTION:

Darifenacin hydrobromide which is chemically (S)-2-{1-[2-(2,3-dihydrobenzofuran-5yl) ethyl]-3-pyrrolidinyl}-2,2-diphenyl acetamide hydrobromide¹, is a potent muscarinic M3 receptor antagonist² that is used to treat symptoms of overactive bladder, such as frequent or urgent urination, and incontinence (urine leakage). According to literature survey, it reveals that, Darifenacin hydrobromide is not official in any of the pharmacopoeia like IP, BP, USP and European pharmacopoeia. To the best of our knowledge there is no method reported for the Assay of Darifenacin hydrobromide in pharmaceutical dosage form by UV spectrophotometry. Existing literature reveals analytical methods like less sensitive colorimetric method³, chiral separation HPLC method⁴ and quite expensive LC-MS/MS method⁵. So, the object of this work is to develop a new, simple, rapid, efficient and reproducible UV spectrophotometric analytical method for the determination of Darifenacin hydrobromide in tablet dosage form.

MATERIALS AND METHOS:

Instrumentation and materials:

A SHIMADZU UV-1700 double beam UV-Visible spectrophotometer (JAPAN) equipped with 10mm matched quartz cells were used in the present study. A SHIMADZU AX-200 single pan balance was used for weighing purpose. All the apparatus and instruments were calibrated and validated before starting the experimental work. Pure Darifenacin hydrobromide obtained from AS Reference Standard Ltd was used as such without further purification. Methanol and Hydrochloric acid (GR grade, Merck) were used in the present study. Commercial tablet formulation ENABLEX (NOVARTIS) containing Darifenacin hydrobromide 15mg were procured from local market.

Preparation of Standard stock solution:

Weighed accurately 15mg of Darifenacin hydrobromide working standard and transfer into a 100ml volumetric flask. It was dissolved in 25ml of methanol and sonicated for 5 minutes. Volume was made with 0.1M Hydrochloric acid and mixed well. The above solution was further diluted to give a 30µg/mL of Darifenacin with 0.1M Hydrochloric acid. This standard solution was scanned over the range of 400-200nm, and the λ_maxwas found to be 284nm.

Figure 1:- UV spectrum of Darifenacin hydrobromide in 0.1M HCl

Figure-2: Linearity graph of DARIFENACIN.

Preparation of sample solution:

Twenty capsules were weighed and the capsule content is taken. A quantity of powder equivalent to 15mg of Darifenacin hydrobromide was accurately weighed and transferred to 100mL volumetric flask. The powder was mixed with 25mL of methanol and sonicated for 10 minutes and made up to volume with 0.1M Hydrochloric acid and filtered through a whatman filter paper. Further dilute 10ml of the filtrate to 50ml with 0.1M Hydrochloric acid and mix well. The absorbance was measured at 284nm. The concentration of the component was obtained by analysis of the spectral data of sample solution with reference to that of the standard. The amount of drug present in each capsule formulation was calculated by using the following formula.

Spl Abs WS 10 100 50 P 426.6

Mg/tablets = ------- X----- X------ X----- X------X-----X--------X A.Wt

Std Abs 100 50 WT 10 100 507.5

Mg/ tablets

% Assay = ---------------------- X 100

Where,

Spl Abs = Sample Absorbance

Std Abs = Standard Absorbance

WS = Weight of Darifenacin Hydrobromide working standard taken in mg

P = % potency of Darifenacin Hydrobromide working standard on as such basis

A.Wt = Average weight of Darifenacin hydrobromide ER tablet

WT = Weight of sample tablet powder

LC = Label claim of Darifenacin tablets.

507.5 = Molecular weight of Darifenacin hydrobromide.

426.6 = Molecular weight of Darifenacin.

Table-1: Quantitative estimation of Darifenacin in Tablet formulation.

Brand

Used

Average*

Std ABS

Average*

Sample ABS

Amount Present

mg/table

% Recovery

% RSD

ENABLEX

0.313

0.311

14.90

99.36

0.11

0.68

Tabel-2: Recovery studies (study of accuracy parameter)

Target

Conc.

Amount added (in mg)

Average

ABS of sample

Amount

recovered

% Recovery

(in mg)

STD

Placebo

80%

25.04

24.31

24.78

325.56

324.98

325.74

0.252

0.264

0.253

24.92

24.21

24.56

99.52

99.58

99.11

100%

30.43

30.21

30.32

319.47

319.72

319.55

0.318

0.313

0.316

30.21

30.34

30.18

99.27

100.43

99.53

120%

36.08

36.02

36.09

313.84

313.92

313.96

0.378

0.379

0.377

35.98

36.11

35.90

99.72

100.24

MEAN

99.69

0.1401

%RSD

0.1405

Table-3: Results of Method Precision

S. No.

Weight Taken

(in mg)

Average ABS

obtained

Assay of Tablet

(in mg)

%Label claim

1. Std

2. Spl-1

3. Spl-2

4. Spl-3

5. Spl-4

6. Spl-5

7. Spl-6

30.1

346.8

352.1

352.7

346.2

349.8

348.6

0.312

0.314

0.311

0.310

0.311

0.309

0.311

15.09

14.95

14.90

14.95

14.85

14.95

100.64

99.67

99.35

99.67

99.04

99.67

MEAN

%RSD

14.95

0.081

0.530

99.67

0.536

0.538

Table-4: Results of Linearity studies.

S. No.

Target concentration

in (µg/mL)

Exact Concentration

Absorbance

80%

90%

100%

110%

120%

130%

20.30

25.90

31.00

36.10

41.20

46.50

0.260

0.290

0.316

0.353

0.380

0.410

Correlation co-efficient

Slope

0.9990

0.0059

Table-5: Summary of validation parameters.

S. No.

Parameters

Value obtained

10.

Absorption maxima

Standard regression equation

Regression Equation (r²)

Accuracy (% Recovery)

System Precision (%RSD)

Method Precision (%RSD)

Range (µg/mL)

Linearity (µg/mL)

LOD (µg/mL)

LOQ (µg/mL)

284nm

y=0.0059x+0.141

0.999

99.69±0.1401

0.86

0.71

5-60

20.00-46.50

RESULTS AND DISCUSSION:

The present study was undertaken to develop a sensitive, precise and accurate UV spectrophotometric method for the estimation of Darifenacin hydrobromide in tablet dosage form. In this method 0.1M Hydrochloric acid was used as solvent. The maximum absorption was found to be 284nm. The linearity range was found to be 20.00 to 46.50µg /mL. The linearity data was subjected to linear regression analysis in order to confirm the linear relationship between concentration and absorbance. The regression co-efficient (R²) value for Darifenacin hydrobromide was found to be 0.999 which indicates the linearity of the method. The percentage recovery of the drug was found to be 99.69±0.141% w/w. Quantitative estimation was subjected to statistical analysis. The RSD value obtained was below 1, indicates precision of the method. The system precision shows RSD values obtained was 0.86 and for method precision the RSD values obtained was 0.71. For the ruggedness analyst to analyst, system to system variability the RSD values obtained was found to be 0.42 and 0.43 for analyst-1 and analyst-2, respectively; 0.22 and 0.23 for system-1 and system-2 respectively. The robustness of the method was confirmed by applying the proposed method by five replicates with changed detection wavelength of 282 and 286nm (±2nm). The %RSD was found to be 0.20 and 0.52 for 282m and 286nm respectively.

CONCLUSION:

Based on the results obtained, it was found that, the proposed method was accurate, precise, reproducible and economical and can be employed for routine quality control of Darifenacin hydrobromide in tablet dosage forms. As the solvent is 0.1M Hydrochloric acid, the method has genuine advantage to use for evaluation of floating and sustained drug delivery systems of Darifenacin hydrobromide effectively.

REFERENCE:

1. http://www.rxlist.com/script/main/darifenacin

2. www.chemicalbook.com/products/darifenacin

3. P.sai Praveen et al. Visible spectrophotometric methods for the determination of darifenacin. Research Journal of Pharmaceutical biological and chemical sciences. Volume 1, issue 2; 2010: 254-255.

4. P.Radhakrishnanand, D.Subba Rao, and V.Himabindu. A Validated LC Method for Determination of the Enantiomeric Purity of Darifenacin in Bulk Drug and Extended Release Tablet. Chromatographia. vol 68, issue 11, 2008, 1059-1062.

5. Barry kaye, William J.Herron, Paul V.macrae, Sylvia Robinson, Rapid, Solid Phase Extraction Technique for the High-Throughput Assay of Darifenacin in Human Plasma. analytical chemistry, 1996, 68(9), 1658-1660.

6. ICH, Q2B (1993). Validation of Analytical Procedure: Methodology, International Conference on Harmonization, Geneva, March1996.

Received on 21.07.2011 Accepted on 10.08.2011

Asian J. Pharm. Ana. 1(3): July-Sept. 2011; Page 43-45