Simultaneous Estimation of Atorvastatin calcium and Nicotinic acid from Tablet Formulation

 

S. Pillai1, I.Singhvi1 and Mousumi Kar2

1Pacific College of Pharmacy, Air port Road, Pratap Nagar Extension, Udaipur (Raj) 313 001

2Department of Pharmaceutical Sciences, Mohan Lal Sukhadia University, Udaipur (Raj) 313 001

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

 

ABSTRACT

Three simple, accurate, economical and reproducible UV spectrophotometric methods for simultaneous estimation of two component drug mixture of atorvastatin calcium and nicotinic acid from combined tablet dosage form have been developed. First developed method involves formation and solving of simultaneous equations using 254.0 nm and 270.0 nm as two wavelengths. Second method is based on two wavelength calculation, wavelengths selected for estimation of atorvastatin calcium were 260.4 nm and 275.6 nm and for nicotinic acid 240.4 nm and 265.2 nm. Third method was developed making use of first order derivative spectroscopy using 233.2 nm and 304.4 nm as zero crossing points for estimation of nicotinic acid and atorvastatin calcium respectively. The results of analysis have been validated statistically and by recovery studies.

 

KEY WORDS                 Spectrophotometric, Atorvastatin calcium, Nicotinic acid.

 

 


INTRODUCTION:

Atorvastatin calcium chemically, 2-(4 – Fluro phenyl)-β δ- dihydroxy-5-(1- methyl ethyl) -3- phenyl-4-[(phenyl amino)-carbonyl]-1H-pyrrole-1- heptanoic acid is an anti hyperlipoproteinemic agent1. Literature survey reveals that for atorvastatin calcium HPLC2-4 methods have been reported. Nicotinic acid, chemically 3-Pyridine carboxylic acid is an anti hyperlipoproteinemic agent and vitamin cofactor5. Few analytical methods for estimation of nicotinic acid from biological fluids including HPLC7-8, LC-MS9 are reported. However none of the spectrophotometric method is yet reported for simultaneous analysis of two drugs from combined pharmaceutical dosage form.

 

MATERIALS AND METHODS:

A Systronics UV/Visible double beam spectrophotometer (model 2101) with 1 cm matched quartz cells was used for spectrophotometric analysis.  Spectra were recorded using specific program of instrument, having specifications as;  spectral band width 2 nm, wavelength accuracy + 0.5 nm, wavelength readability 0.1 nm increment. Different batches of the tablet samples of combined dosage form of atorvastatin calcium and nicotinic acid were procured from the local pharmacy.

 

 

eight dilutions of standard in concentration range of 2-40 mg/ml of atorvastatin calcium and 5 – 70 mg/ml of nicotinic acid. All solutions were scanned in wavelength range of 220.0 nm and 380.0 nm. Fig.1 represents the overlain spectra of atorvastatin calcium and nicotinic acid in methanol. Two wavelengths selected for formation and solving of simultaneous equations were 254.0 nm and 270.0 nm. Absorptivity coefficients of both the drugs were determined at selected wavelengths. Absorptivity coefficient for atorvastatin calcium at 254.0 nm and 270.0 nm were 495.33 and 397.33 cm-1 g-1 L while respective values for nicotinic acid were 143.75 and 245.69 cm-1 g-1 L

 

Set of two simultaneous equations thus formed are

A1     =   495.33 C1   +    143.75 C2        -----   I

A2     =   397.33 C1    +   245.69 C2        -----    II

 

Where, A1 and A2 are absorbance of sample solution at 254.0nm and 270.0 nm respectively. C1 and C2 are concentration of atorvastatin calcium and nicotinic acid respectively in sample solution in g/l. Validity of above framed simultaneous equations was checked by preparing five mixed standards using pure drug sample of two drugs, results of which are reported in Table 1. 

 

Analysis of commercial formulation

Twenty tablets of each marketed formulations were accurately weighed and average weight per tablet was determined, tablets were crushed to fine powder and powder equivalent to 500 mg of nicotinic acid was accurately weighed and extracted four times with 20 ml portions of methanol and filtered through Whatman filter paper no. 41 into a 100 ml volumetric flask and volume was made up to the mark with the same. From the above filtrate 5 ml was further diluted to 50 ml with methanol in a volumetric flask. Finally 1 ml was taken in 10 ml volumetric flask to which 1.9 ml of 100 µg/ml pure drug stock solution of atorvastatin calcium was added, volume made up to the mark and the absorbance of this final diluted sample solution was measured at 254.0 nm and 270.0 nm respectively and concentration of two drugs in the sample were calculated using above framed simultaneous equations I and II. Results of analysis of tablet formulation are reported in Table 2.

 

Fig 1: Overlain spectra of two drugs

A: Spectra of atorvastatin calcium in methanol. B: Spectra of nicotinic acid in methanol.

 

Methods II: Using Two Wavelength Calculation

From absorption spectra of atorvastatin calcium and nicotinic acid (fig.1), set of two wavelengths l1 (260.4 nm) and l2 (275.6 nm) for estimation of atorvastatin calcium and l3 (240.4 nm) and l4 (265.2 nm) for estimation of nicotinic acid were selected on basis of principle that absorbance difference between two points on a mixture spectra is directly proportional to concentration of component of interest and independent of interfering component. Five mixed standard of pure drug containing different concentration of two drugs were prepared in methanol. All standards were scanned at respective set of selected wavelengths. Absorbance difference was measured and respective calibration curve was plotted. Validity of proposed method was checked by preparing five mixed standards using pure drug sample of two drugs and absorbance difference values was measured at respective selected set of wavelength and determined concentration of two drugs using respective calibration curve. Results of validation studies are reported in table 1. Tablet sample solution was prepared in similar manner as for method-I, final sample solution was analyzed by scanning at respective set of wavelength and determined absorbance difference values were noted, the concentration of atorvastatin calcium and nicotinic acid was calculated from the respective calibration curve. Result of analysis is reported in Table 2.

 

Method III: Employing first order derivative spectroscopy

From the first order derivative spectra of atorvastatin calcium and nicotinic acid in methanol (fig.2) zero crossing points 233.2 nm and 304.4 nm were selected for simultaneous estimation of two drugs. Pure drug sample was prepared similar to method I and eight dilutions were made in the concentration range of 2-40 mg/ml of atorvastatin calcium and 5 – 70 mg/ml of nicotinic acid. The absorbance of these dilutions was recorded in first derivative mode at 304.4 nm for estimation of atorvastatin calcium and 233.2 nm for estimation of nicotinic acid and respective calibration curves were prepared. Validity of proposed method was checked by preparing five mixed standards using pure drug sample of two drugs and absorbance was measured at respective selected zero crossing points in first derivative mode and determined concentration of two drugs using respective calibration curve. Results of validation studies are reported in table 1.

 

Tablet sample solution was prepared in similar manner as for method-I, absorbance of final sample solution was determined at respective zero crossing point in first derivative the concentration of atorvastatin calcium and nicotinic acid was calculated from the respective calibration curve. Result of analysis is reported in Table 2.

 

Fig 2: Overlain first order derivative spectra of two drugs

A: First order derivative spectra of atorvastatin calcium in methanol. B: First order derivative spectra of nicotinic acid in methanol.

 

RECOVERY STUDIES:

To study the accuracy, reproducibility and precision of the above developed methods recovery studies were carried out by addition of standard drug stock solution to pre-analyzed tablet sample solutions at three different concentration levels. Results of recovery studies were found to be satisfactory and are reported in Table 2.

 

RESULT AND DISCUSSION:

Three spectrophotometric methods have been developed for simultaneous estimation of atorvastatin calcium and nicotinic acid from combined tablet dosage form. The first developed method involving formation and solving of simultaneous equations is very simple and requires only accurate determination of  absorbance of the sample at two selected wavelengths  and few calculations that can be manually done, thus method can be used with any model of spectrophotometer. Once the equations are framed the


 

TABLE 1: RESULTS OF VALIDATION STUDIES FOR METHOD I, II AND III USING MIXED STANDARDS

 

Sample No.

Conc. Present (mcg/ml)

% Conc. Found

 

 

Method I

Method II

Method III

ATS

NA

ATS

NA

ATS

NA

ATS

NA

1

2

3

4

5

5

10

15

20

25

25

20

15

10

05

99.66

98.01

100.10

100.60

99.83

100.77

98.61

101.40

100.27

100.33

99.22

99.82

98.94

100.02

100.22

99365

99.07

99.41

100.23

99.29

99.40

99.60

100.46

100.45

99.72

99.72

99.60

100.40

100.20

99.60

ATS: Atorvastatin calcium        NA: Nicotinic acid

 

Table 2: RESULTS OF ANALYSIS OF COMMERCIAL FORMULATION

 

Method

Formulation

Label claim(mg/tab)

% of label claim estimated*

Standard Deviation

% Recovery**

ATS

NA

ATS

NA

ATS

NA

ATS

NA

Method I

 

Method II

 

Method III

A

B

A

B

A

B

10

10

10

10

10

10

500

500

500

500

500

500

100.50

100.47

99.11

100.33

98.50

98.67

100.93

99.66

99.36

100.73

99.61

98.77

0.887

0.973

0.254

0.827

1.345

0.795

0.471

0.627

0.158

0.417

0.354

0.829

100.27

99.62

99.50

100.74

99.36

99.97

100.41

99.83

100.43

99.61

99.18

100.69

* Average of five determinations   ** Average of recovery studies at three different concentration level

 


 

method is very fast. Framed equations were validated using laboratory prepared mixed standards of two drugs which gave satisfactory results.  Second developed method for simultaneous analysis of atorvastatin calcium and nicotinic acid make use of two wavelength calculation so as to remove interference between two components. Proper selection of two wavelengths for estimation of a component is critical.

The third developed method for simultaneous estimation of two drugs from combined dosage form make use of first order derivative ultraviolet spectrophotometry based on principle that at zero crossing point of one component the other component has substantial absorbance.

The result of analysis of two drugs from of tablet formulation using these developed methods were found close to 100% for both atorvastatin calcium and nicotinic acid , values of standard deviation was satisfactorily low indicating accuracy and reproducibility of the methods. Recovery studies were satisfactory which shows that there is no interference of excipients. The developed methods were found to be simple, rapid, accurate and can be used for routine analysis of two drugs from combined tablet formulations

 

REFERENCES:

 

1.  Budvari S. The Merck Index, 12th Edn., Merck and Co., Inc., White house Station, NJ, 1996, 146.

2.  Ravikumar BVV, et al. Development of reverse phase HPLC method for the simultaneous estimation of atorvastatin and aspirin in bulk and formulations.  57th Indian Pharmaceutical Congress, Scientific Abstracts. 2005; 289.

3.  Lamba HS, et al. Simultaneous determination of atorvastatin and ezetimibe in a combination tablet by HPLC. 57th Indian Pharmaceutical Congress, Scientific Abstracts. 2005; 297.

4.  Lamba HS, et al. Simultaneous determination of atorvastatin and amlodipine besylate in tablets by RP-HPLC. 57th Indian Pharmaceutical Congress, Scientific Abstracts. 2005; 300.

5.  Budvari S. The Merck Index, 12th Edn., Merck and Co., Inc., White house Station, NJ, 1996, 1120.

6.  Shibata K, Kawada T and Iwai K.Simultaneous microdetermination of nicotinamide and its major metabolites N1-methyl 2- pyridone-5- carboxamide and N1-methyl 4- pyridine-3- caroxamide by HPLC.  J Chromatogr. 1988; 424(1): 23.

7.  McKee RW, et al. Detemination of nicotinamide and metabolic products in urine by HPLC. J Chromatogr. 1982; 230(2): 309.

8.  Shaikh B, et al. Determinationof N-methyl nicotinamide in urine by HPLC. J Chromatogr Sci. 1977; 15(6): 215.

9.  Catz P, et al. Simultaneous determination of myristyl nicotinate, nicotinic acid and nicotinamide in rabbit plasma by LC-tandem mass spectroscopy using methyl ethyl ketone as a deproteinization solvent. J Chromatogr B Analyt Technol Biomed Life Sci. 2005; 829(1-2): 123.

 

 

 

 

 

 

Received on 05.03.2008          Modified on 10.03.2008

Accepted on 24.03.2008         © RJPT All right reserved

Research J. Pharm. and Tech. 1(2): April-June. 2008;Page83-85