New Method for Spectrophotometric Estimation of New Anti Epileptic Drugs in Solid Dosage Form
*MOHAN A and GHOSH SK
Dibrugarh University, Dibrugarh, Assam. India
*Corresponding Author E-mail: mo_arti89@yahoo.co.in
ABSTRACT
The present paper describes a simple, sensitive, accurate and reproducible method for spectrophotometric estimation of some new antiepileptic drugs like Oxcarbazepine and Lamotrigine in bulk and solid dosage forms. Oxcarbazepine and Lamotrigine are antiepileptic and mood stabilizing drugs used primarily in the treatment of epilepsy and bipolar disorder.Oxcarbazepine is a structural derivative of Carbamazepine, adding extra oxygen to the dibenzepine ring whereas Lamotrigine is a diamine with dichlorodiphenyl groups. A visible double beam spectrophotometer with a matched pair of 1 centimeter quartz cell was used for experimental purposes and analytical reagent grade acetonitrile in distilled water was used as a solvent. Oxcarbazepine showed maximum absorbance at a wavelength of 257 nm and obeyed Beer’s law in the concentration range of 2-50 mcg/ml. Previously reported spectrophotometric method as observed in literature survey gives a method based on the formation of a coloured complex. The present communication, a simple spectrophotometric method is developed for the estimation of Oxcarbazepine in its solid dosage form using distilled water as a solvent.
Lamotrigine showed maximum absorbance at a wavelength of 304 nm and obeyed Beer’s law in the concentration range of 10-50 mcg/ml.Previously reported spectrophotometric method as observed in literature survey gives a method which uses methanol as a solvent which might not be suitable for oral dosage form .The present communication using distilled water as a solvent is therefore more convenient, accurate and reproducible.
The results of the analysis were validated statistically and by recovery studies.
INTRODUCTION:
Oxcarbazepine is an antiepileptic and mood stabilising drug, used primarily in the treatment of epilepsy and bipolar disorder(1). Oxcarbazepine is a structural derivative of Carbazepine, adding extra oxygen to Dibenzepine ring. Oxcarbazepine is 10, 11 –Dihydro -10 – oxo - 5H - dibenz (b, f) azepine-5-carboxamide.
.
OXCARBAZEPINE
Previously reported spectrophotometric method as observed in literature survey (2) gives a method based on the formation of a coloured complex. The present communication, a simple spectrophotometric method is developed for the estimation of Oxcarbazepine in bulk drug and its tablet formulation using distilled water as a solvent.
Lamotrigine is one of the newer antiepileptic drugs, with fewer side effects, which is marketed in UK since 1992 and introduced in India recently (3). Chemically it is 6(2,3- dichlorophenyle) – 1,2,4 triazine 3,5 diamine. It is official in Martindale Extra Pharmacopoeia(4).
LAMOTRIGINE
Table: 1 optimum conditions, optical characteristics and statistical data of the regression equation. For oxcarbazepine:
|
PARAMETERS |
VALUE |
|
Absorption maximum (nm) |
256 |
|
Beer’s Law limit (mcg/ml) |
2-50 |
|
Correlation coefficient |
0.9999 |
|
Regression equation |
Y=Ax-b |
|
Slope(A) |
0.02 |
|
Intercept (b) |
0.003 |
For Lamotrigine
|
PARAMETERS |
VALUE |
|
Absorption maximum (nm) |
304 |
|
Beer’s Law limit (mcg/ml) |
10-50 |
|
Correlation coefficient |
0.8288 |
|
Regression equation |
Y=Ax-b |
|
Slope(A) |
0.00415 |
|
Intercept (b) |
0.004 |
Literature survey (5) gives a method which uses methanol as a solvent which might not be suitable for oral solid dosage form. The present method using distilled water as a solvent is more convenient and accurate.
METHOD:
Method for Oxcarbazepine:
Standard stock solution was prepared by dissolving 10 mg of Oxcarbazepine in 20 ml of AR grade acetonitrile and the volume was made up to100 ml with distilled water. The final concentration of this being 0.1ml/mg.Different aliquots were taken from stock solution and diluted with distilled water to prepare a series of concentration of 2-100 mcg/ml. The solution was scanned on spectrophotometer in the spectrum and their absorbances were measured at about 257 nm using acetonitrile in distilled water as blank. The calibration curve was found to be linear in the range of 2-50 mcg/ml. The linear regression of absorbance on concentration gave the equation y=Ax-b with a correlation coefficient of 0.9999 that indicates a good linearity between absorbance and concentration in the range of 2-50 mcg/ml. The slope, intercept, correlation-coefficient and optical characterstics are summarized in table.1.
Recovery studies were performed as well. Twenty tablets of a single batch were weighed and powered. A quantity of powder equivalent to 10 mg of Oxcarbazepine was weighed accurately and transferred to a 100 ml volumetric flask. 20 ml of acetonitrile was added to solubilise the drug and volume made up to 100 ml with distilled water.
The solution was further diluted to get four different concentrations of 2, 10, 20, 40, mcg / ml of Oxcarbazepine. The absorbances of these solutions were measured at 257 nm using acetonitrile in water as blank. The content of Oxcarbazepine in the preparation was calculated from the standard curve. The results are mentioned in Table 2
Table: 2 Results of estimation of oxcarbazepine in tablets.
|
Sample Number |
Labeled amount (mg) |
Amount found (mg) By proposed method ± SD |
Recovery %age |
|
1. |
10 |
9.9 ± 0.07 |
99% |
|
2. |
10 |
9.8± 0.04 |
98% |
|
3. |
10 |
9.6± 0.04 |
96% |
|
4. |
10 |
9.9± 0.04 |
99% |
Results of estimation of lamotrigine in tablets.
|
Sample Number |
Labeled amount (mg) |
Amount found (mg) By proposed method ± SD |
Recovery %age |
|
1. |
10 |
8.5 ± 0.07 |
85% |
|
2. |
10 |
8.2± 0.04 |
82% |
|
3. |
10 |
8.5± 0.04 |
85% |
|
4. |
10 |
8.5± 0.04 |
85% |
Method for Lamotrigine:
Standard stock solution was prepared by dissolving 10 mg of Lamotrigine in 10 ml of AR grade acetonitrile and the volume was made up to100 ml with distilled water. The final concentration of this being 0.1ml/mg Stock solution samples were diluted with distilled water to prepare a series of concentration of 10-100 mcg/ml. The solution was scanned and their absorbances were measured at about 304 nm using acetonitrile in distilled water as blank. The calibration curve was found to be linear in the range of 10-50 mcg/ml. The linear regression of absorbance on concentration gave the equation y=Ax-b with a correlation coefficient of 0.8288 that indicates a good linearity between the range of 10-50 mcg/ml. The slope, intercept, correlation-coefficient and optical characteristics are summarized in table 1.
Recovery studies :Twenty tablets of a single batch were weighed and powered. A quantity of powder equivalent to 10 mg of Lamotrigine was weighed and transferred to a 100 ml volumetric flask. 10 ml of acetonitrile was added and volume made up to 100 ml with distilled water.
The solution was further diluted to get four different concentrations of 10, 20, 30, 40, 50 mcg / ml of Lamotrigine. The absorbances of these solutions were measured at 304 nm using acetonitrile in water as blank. The content of Lamotrigine was calculated from the standard curve. The results are mentioned in Table 2
RESULTS:
The results of analysis have been shown in table 1 and 2.
CONCLUSION:
The % recovery value, which is close to 100%, indicates reproducibility of the method and absence of interference of the excepients present in the formulation. The authors conclude that the proposed spectrophotometeric method for the estimation of oxcarbazepine and lamotrigine are simple, convenient, accurate, sensitive and reproducible. The method can be used for routine analysis of oxcarbazepine and lamotrigine in bulk as well as in tablet dosage form as an alternative to existing spectrophotometric method.
1. Oxcarbazepine- Wikipedia, the free encyclopedia. en. wikipedia. org/ wiki/oxcarbzepin
2. Malke Sheetal, Shindhaye Supriya, Kadam VJ,Indian Journal of Pharmaceutical Sciences,2007,69(2),pg 211-214
3. Lamotrigine-Wikipedia, the free encyclopedia. en. wikipedia. org/wiki/Lamotrigine
4. Martindale: The extra pharmacopoeia (29th ed)
5. Talekar RS, Dhake AS, Sonaje DB and Mourya VK, Indian Journal of Pharmaceutical Sciences, 2000, 69(2),pg 51-52.
Received on 04.08.2009 Modified on 09.08.2009
Accepted on 17.08.2009 © AJRC All right reserved
Asian J. Research Chem. 2(3): July-Sept., 2009, page 322-324