Simultaneous Spectrophotometric Estimation of Simvastatin and Ezetimibe in Tablet Formulation.
N. M. BHATIA*, D. D. DESHMUKH, S. U. KOKIL AND M. S. BHATIA
Department of Pharmaceutical Chemistry, Bharati Vidyapeeth College of Pharmacy,
Near Chitranagri, Kolhapur-416013.
*For correspondence: neelabhatia@yahoo.co.uk
Abstract:
A simple, sensitive and rapid spectrophotometric method has been developed for simultaneous estimation of simvastatin and ezetimibe in tablet formulation. Multi-wavelength method was used to eliminate interference due to absorbance of ezetimibe at the sampling wavelength for simvastatin and absorbance of simvastatin at the sampling wavelength for ezetimibe. A calibration curve was obtained for simvastatin by plotting the difference in absorbance between 223 nm and 253 nm, in the concentration range of 0 to 25 ?g/ml against six mixed standard solutions. Similarly a calibration curve was plotted for ezetimibe at 258 nm in the concentration range of 0 to 25 ?g/ml against the six mixed standard solutions. Both the drugs obey Beer's law in the concentration ranges employed for analysis. Results of analysis were validated statistically and by recovery studies. The percentage of label claim ? standard deviation was 102.69 ? 0.36 for simvastatin and 99.43 ? 0.87 for ezetimibe. The percentage recovery ? standard deviation for simvastatin was 102.17 ? 0.83 and for ezetimibe was 99.68 ? 0.66.
Introduction:
Simvastatin, (SM) chemically 2, 2-Dimethyl butanoic acid (1S, 3R, 7S, 8S, 8aR)-1, 2, 3, 7, 8, 8a-hexahydro-3-7-dimethyl-8-[2-(2R, 4R) - tetrahydro-4-hydroxy-6-oxo-2H-pyran-2-yl] ethyl]-1-napthalenenyl ester is a reversible inhibitor of the microso-malenzyme 3-hydroxy-3-methylglutaryl-coenzyme-A (HMG-CoA) reductase. The drug is synthesized from a fermentation product of Aspergillus terreus and widely used in the treatment of various types of hypercholesterolemia. Literature survey revealed that HPLC1-2, LC-MS-MS3, MEKC4, second derivative UV spectrophotometric method5 for estimation of SM from pharmaceutical dosage form, biological systems and its derivatives have been reported. Ezetimibe, chemically 1- (4-flurophenyl)-3(R)-[3-(4-flurophenyl)-3(S)-hydroxypropyl]-4(S)-(4-hydroxyphenyl)-2-azetidione is a selective inhibitor of intestinal cholesterol. The drug is widely used in treatment of hypercholesterolemia and sitosterolemia. Literature survey revealed that several RP-HPLC6-8, LC-MS-MS9 and spectrophotometric methods10 for the estimation of EZ in pharmaceutical dosage form and from biological system have been reported. A PC based Jasco V-530 recording UV/VIS spectrophotometer was employed for all measurements using a matched pair of 10 mm quartz cells. Drug samples of SM and EZ were procured from Lupin pharmaceuticals Ltd, Mumbai.
Experimental:
Standard stock solutions containing 100 ?g/ml of SM and EZ were prepared separately by dissolving 10 mg of drug in 40 ml of methanol and then final volume of both the solutions was made up to mark with methanol in 100 ml volumetric flasks to get a stock solutions containing 100 ?g/ml of SM and EZ respectively. From these stock solutions, working standard solutions of both drugs containing 10?g/ml were prepared by appropriate dilutions. Working standard solutions were scanned in the UV region of 200-400 nm to determine wavelength of maximum absorption. The wavelength of maximum absorption was found to be 237 nm and 232 nm for SM and EZ respectively. Multi-wavelength method was employed for analysis of the two drugs. The selection of method and wavelength was done after observing overlain spectra of two drugs (fig. 1). For estimation of SM the two wavelengths were so selected that one of the wavelength 223 nm was the wavelength other than the wavelength of absorbance maxima of SM and the second wavelength 253 nm was used to eliminate interference due to the absorbance of EZ, where as EZ was directly estimated at 258 nm. For calibration curves, stock solutions of SM and EZ were appropriately diluted to obtain concentration range of 0-25 ?g/ml for each drug. Calibration curves were constructed for each drug by plotting absorbance difference at selected wavelengths of each drug against its concentration. By using the quantitative mode of instrument, intercept and slope values were obtained. Data of regression analysis are given in Table-1. The concentrations of these two drugs were calculated using equations, AbsSM = A+ B ? CSM .....(1), AbsEZ = A + B ? CEZ..... (2), where CSM= concentration of SM, CEZ = concentration of EZ, AbsSM= absorbance difference of SM at 223 and 253 nm, AbsEze= absorbance of EZ at 258 nm.. By applying the slope and intercept values so obtained, the concentration of SM and EZ can be found out using formula AbsSM= -0.0058 + 0.0344 ? CSM and AbsEZ = -0.0020+ 0.0291 ? CEZ.
Marketed tablet formulations containing 10 mg of SM and EZ procured from a local pharmacy were analyzed using this method. From the triturate of the 20 tablets, an amount equivalent to 10 mg of SM and 10 mg of EZ was weighed and dissolved in 40 ml of methanol. The solution was filtered through whatmann filter paper no. 41 and then final volume of the solution was made up to mark with methanol in 100 ml volumetric flask to get a stock solution containing 100 ?g/ml of SM and EZ. After appropriate dilutions the absorbances were measured and the concentration of each analyte was determined with the equations generated in the method.
Results and Discussions:
The statistical data of the results obtained after replicated determination (n=6) are shown in the Table 2. Accuracy and sensitivity of the method was checked by performing recovery studies by spiking different concentrations of pure drug in the preanalyzed tablet sample. Statistical data for the recovery studies are given in Table- 3 (n=5).
The proposed method for simultaneous estimation of SM and EZ was found to be simple, economical, accurate, rapid and reproducible for routine simultaneous estimation of the two drugs in tablet formulation. The recoveries obtained for each drug (Table-3) do not differ significantly from 100% and thus confirms the accuracy and sensitivity of the method. Result of analysis of tablet formulations indicated that there is no interference of
the common excipients used in the tablet formulation and the method can be adopted for the routine analysis of formulations containing these drugs.
ACKNOWLEDGEMENT:
The authors are thankful to Lupin pharmaceuticals Ltd, Mumbai for supplying gift samples of SM and EZ to carry out this work. The team acknowledges Dr. H. N. More, Principal, Bharati Vidyapeeth College of Pharmacy, Kolhapur for providing necessary facilities for this work.
REFERENCES:
1.Gandhimathi, M., Ravi, T. K., Varghese, A. and Ninan, A., Indian Drugs, Dec. 2003, 40(12), 707.
2.Ochiai, H., Uchiyama, N., Imagaki, K., Hata, S. and Kamei, T., J. Chromatogr. B., 1997, 694, 211.
3.Jemal, M., Ouyang, Z. and Powell, M. L., J. Pharm. Biomed. Anal., 2000, 23, 323.
4.Srinivasu, M. K., Raju, A. N. and Om Reddy, G., J. Pharm. Biomed. Anal., 2002, 29, 715.
5.Wang, L. and Asgharnejad, M., J. Pharm. Biomed. Anal., 2000, 21, 1243.
6.Sistla, R., Tata, V. S. S. K., Kashyap, Y. V., Chandrasekar, D. and Diwan, P. V., J. Pharm. Biomed. Anal., 2005, 39, 517.
7.Singh, S., Singh, B., Bahuguna, R., Wadhwa, L. and Saxena, R., J. Pharm. Biomed. Anal., 2006, 41, 1037.
8.Sankar, D. G. and Kumar, D. V. S. P., Asian J. Chem., 2006, 18(2), 823.
9.Oswald, S., Eberhard, S., Cascorbi, I. and Siegmund, W., J. Chromatogr. B., 2006, 830, 143.
10.Sankar, D. G., Sumanth, S. K., Pawar, A. K. M. and Madhvi Latha, P. V., Asian J. Chem., 2006, 18(2), 1526.
TABLE-1: Result of Regression Analysis:
ParametersSMEZ
?max237 nm232 nm.
Beer's law limit0-25 ?g/ml0-25 ?g/ml
Regression data
Slope0.03440.0291
Intercept-0.0058-0.0020
Correlation coefficient0.99780.9993
Mean Recovery (%)102.1799.68
TABLE-2: Result of Analysis of Tablet Formulation:
Formulation
AnalyteLabel
claim
(mg)% Label claim Estimated*
(Mean ? S. D.)Coefficient
of
Variance
Tablet -1SM10102.69? 0.3680.358
EZ10 99.12 ? 0.3810.384
Tablet -2SM10101.97 ? 0.5070.497
EZ1099.43 ? 0.8730.878
*Average of six determinations
TABLE-3: Result of Recovery Studies:
Formulation
AnalyteLabel
claim
(mg)% Recovery Estimated*
(Mean ? S. D.)Coefficient
of
Variance
Tablet -1 SM10102.17 ? 0.8340.816
EZ1099.68 ? 0.6620.664
Tablet - 2 SM10103.13 ? 0.3170.307
EZ1098.26 ? 0.8130.827
*Average of six determinations
Fig. No. 1. Overlain Spectra of SM and EZ