Development and Validation of Spectrophotometric Methods for Quantitative Estimation of Pramipexole Dihydrochloride in bulk and Pharmaceutical Dosage Form

 

Satish Middi*, Shobha Manjunath

Department of Pharmaceutical Analysis, H.K.E.Ss Taradevi Rampure Institute of Pharmaceutical Sciences, Sedam Road, Gulbarga-585105, Karnataka, India

*Corresponding Author E-mail: satishmiddi@gmail.com

ABSTRACT:

Two simple and sensitive spectrophotometric methods (A and B) in visible region have been developed for the estimation of Pramipexole dihydrochloride in pure and pharmaceutical formulations. Method A and B is based on the condensation of heterocyclic amino group of Pramipexole with Para-dimethyl aminocinnamaldehyde (PDACA) and vanillin in presence of acidic media i.e. conc. Hydrochloride to form a colored chromogen with a characteristic absorption maximum at 525nm and 425nm respectively. Beer's law is obeyed in the concentration range of 50-350g/mL and 10-50g/mL for Method A and B respectively. The results obtained with the proposed methods are in good agreement with labeled amounts when the marketed pharmaceutical formulations are analyzed. The results of analysis have been validated statistically and by recovery studies.

 

KEYWORDS: Para-dimethylamino cinnamaldehyde, vanillin, Chromogen, Pramipexole, recovery.

 


INTRODUCTION:

Pramipexole dihydrochloride is chemically (s)-2-amino-4,5,6,7-tetrahydro-6-(propylamino) benzothiazole dihydrochloride is an antiparkinsonian drug used to treat early and advanced parkinsons disease and recently approved in US and Europe for the treatment of idiopathic restless legs syndrome in adults1. Parkinsons disease is chronic neurodegenerative disease characterized by bradykinesia, predominantly affecting the elderly. It occurs when certain nerve cells (neurons) in a part of brain called substantia nigra die or become impaired. Normally, these neurons produce a vital chemical known as dopamine which allows smooth, coordinated function of the bodys muscles and movement2.

 

Pramipexole dihydrochloride

 

It is not official in any of the Pharmacopeias. It is listed in the Merck Index3 and Martindale: The complete drug reference4. Literature survey reveals that a few methods based on HPLC5, 6, LC-MS7 are reported for the determination of Pramipexole in biological fluids. Analytical procedures were reported for the determination of dissociation constant values of Pramipexole by HPLC8 method, an RP-HPLC9 method and simple spectrophotometric methods10-15 have also been reported for the estimation of Pramipexole in bulk drug and formulations. The present investigation has been undertaken to develop two simple and accurate colorimetric methods using PDACA and vanillin.

 

MATERIALS AND METHODS:

INSTRUMENT:

All spectral measurements were made on shimadzu 1800 UV-Visible spectrophotometer with 1 cm matched quartz cells.

 

MATERIALS:

Pure sample of Pramipexole was obtained from Sun Pharmaceutical Ltd, Jammu and Kashmir, India and commercial formulations were procured from local market. All the chemicals used were of analytical grade.

 

REAGENTS:

  Ethanolic solution of Para-dimethylamino cinnamaldehyde (1%w/v)

  Conc. Hydrochloric acid.

  Ethanolic solution of vanillin (2%w/v)

 

Preparation of standard drug solution:

Accurately weighed 100 mg of Pramipexole was transferred into 100 mL volumetric flask and dissolve in sufficient quantity of distilled Ethanol and volume was made up with distilled Ethanol to obtain concentration of 1000g/mL.

 

Preparation of sample drug solution:

For the sample solution, tablets of Pramipexole dihydrochloride were accurately weighed and average weight per tablet was determined. The tablets were powdered and powder equivalent to 100mg of drug was taken into 100mL volumetric flask and dissolve in sufficient quantity of distilled Ethanol and made up to 100mL with distilled ethanol and filtered. The concentration of solution was 1000g/mL.

 

Assay Procedure:

Method A:

Aliquots of standard drug solution ranging from 0.5 to 3.5mL (1mL=1000g/mL) were transferred into a series of 10mL volumetric flask. To each flask 1.0 mL of ethanolic para-dimethyl amino cinnamaldehyde(1%w/v), four drops of conc.hydrochloride were added and heated for 15min at 40c and the volume was made up to the mark with distilled ethanol. The absorbance of orange red colored chromogen was measured at 525nm against a reagent blank. The amount of drug present in the sample was computed from its calibration curve.

 

Table 1: Summary of Validation Parameters

Parameters

Method A

Method B

λmax (nm)

525

425

Beers Law Limit (g mL-1) (C)

50-350

10-50

Molar absorptivity

(L mole-1 cm-1)

0.836103

1.87 x 104

Regression Equation (Y*)

Slope (b)

 

0.0029

 

0.016

Intercept (a)

-0.1256

0.004

Correlation Coefficient (r)

0.9996

0.9992

%RSD

0.1842

0.179

Range of errors**

Confidence limits with 0.05 level

Confidence limits with 0.01 level

 

0.0005

0.0008

 

0.0008

0.0012

Limit of Detection (LOD)

0.8339

0.197

Limit of Quantification (LOQ)

2.527

0.598

 

Method B:

Fresh aliquots of Pramipexole ranging from 1 to 5 mL (1 mL-100g/mL) were transferred into a series of 10 mL volumetric flasks to provide final concentration range of 10 to 50 μg/mL. To each flask 2mL of ethanolic vanillin (2% w/v) solution and 0.5 mL of conc. HCl were added and heated at 40c for 15 min. The solutions were cooled to room temperature and made up to mark with distilled ethanol. The absorbance of orange yellow colored chromogen was measured at 425 nm against the reagent blank. Stability of the color was found to be 70 min. The amount of Pramipexole present in the sample solution was computed from its calibration curve.

 

RESULTS AND DISCUSSION:

The optical characteristics such as Beer's law limits, molar absorptivity were calculated and the results are summarized in Table 1.

 

Y*= bC+a

Where. C is the concentration of Pramipexole in g mL-1 and Y is the absorbance at the respective λmax.

 

For eight measurements:

The regression analysis using the method of least squares was made for the slope (b), intercept (a) and correlation coefficient (r) obtained from different concentrations and the results are summarized in Table.1. The percent relative standard deviation and percent range of error (0.05 and 0.01 level of confidence limits) calculated from the eight measurements, of the upper Beers law limits of Pramipexole are given in Table.1. The results showed that these methods have reasonable precision. The optimum conditions for color development for Method A and B were established by varying the parameters one at a time and keeping the other parameters fixed and observing the effects of product on the absorbance of the colored species and incorporated in the procedures.(Table 3 and 4).

 

In order to justify the reliability and suitability of the proposed methods, known quantities of pure Pramipexole dihydrochloride was added to its various preanalysed formulations and the mixtures were analysed by the proposed methods. The results of recovery experiments are summarized in Table 2. The other active ingredients and excipients usually present in pharmaceutical dosage forms did not interfere.

 

ACKNOWLEDGEMENT:

We are thankful to Sun Pharmaceuticals Ltd, Jammu and Kashmir for providing us the gift sample of the pure drug and to the Principal, H.K.E.Societys Matoshree Taradevi Rampure Institute of Pharmaceutical Sciences, Gulbarga for providing research facilities.

 


 

Table 2: Results of Assay

Sample

Labeled amount (mg)

Amount found by the Proposed method (mg)

% Recovery by the proposed method

Method A

Method B

Method A

Method B

T1

1

0.995

0.996

99.51

99.63

T2

1

0.987

0.989

98.72

98.94

Table 3:-Optimum conditions for establishing the Method A

Parameter

Optimum range

Conditions in. procedure

Remarks

λmax (nm)

520-530

525nm

 

Volume of PDACA

0.8mL to 1.5mL

1mL

Variation of volume below and above range gave change in absorbance

Effect of volume of conc Hydrochloric acid on color development

2 drops to 6 drops

4 drops

2 drops of conc.Hydrochloric acid results in low absorbance values and 6 drops results in instability of the colored product.

Effect of order of addition of reagents on color development

 

Pramipexole, PDACA, conc.HCl

 

If the order of addition changed low absorbance values resulted.

Effect of temperature and time

35-45c

40c, 15min

Above 45c distlled ethanol evaporates.

Solvent for dilution

Distilled ethanol

Distilled ethanol

It gives low absorbance in case of water instead of using distilled Ethanol

Color stability

Immediate after-70min

5min

Absorbance of colored product decreases slowly with time after 70 min.

 

Table 4:-Optimum conditions for establishing the Method B

Parameter

Optimum range

Conditions in procedure

Remarks

λmax (nm)

420-430

425

 

Volume of vanillin

1.5mL to 2.5mL

1mL

Variation of volume below and above range gave change in absorbance

Effect of volume of conc. Hydrochloric acid on color development

0.2mL to 0.8mL

 

 

0.5mL

 

 

0.2mL of conc. Hydrochloric acid results in low absorbance values and 0.8mL results in instability of the colored product.

Effect of order of addition of reagents on color development

 

 

Pramipexole, vanillin, conc.HCl

If the order of addition changed low absorbance values resulted.

Effect of temperature and time

35-45c

40c, 15min

Above 45c distilled ethanol evaporates.

Solvent for dilution

Distilled ethanol

Distilled ethanol

It gives low absorbance in case of water instead of using distilled ethanol

Color stability

Immediate after-70min

10min

Absorbance of colored product decreases slowly with time after 70 min.


Selection of Wavelength for Pramipexole. Method A

Calibration curve of Pramipexole Method A

Selection of Wavelength for Pramipexole. Method B

Calibration curve of Pramipexole Method B

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Received on 09.04.2012 Modified on 28.04.2012

Accepted on 20.05.2012 RJPT All right reserved

Research J. Pharm. and Tech. 5(6): June 2012; Page 764-767