NEW VALIDATED STABILITY INDICATING RP-HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF AMLODIPINE BESYLATE AND VALSARTAN IN PHARMACEUTICAL FORMULATION

NEW VALIDATED STABILITY INDICATING RP-HPLC METHOD FOR SIMULTANEOUS ESTIMATION OF AMLODIPINE BESYLATE AND VALSARTAN IN PHARMACEUTICAL FORMULATION

T. Hemant Kumar ^* and C. H. Asha

Department of Pharmaceutical Analysis and Quality Assurance, Vignan Institute of Pharmaceutical Technology, Duvvada, Vishakapatnam - 530049, Andhra Pradesh, India.

ABSTRACT: A simple, specific, accurate and precise and stability indicating RP-HPLC method was developed and validated for the simultaneous estimation of Amlodipine Besylate and Valsartan in pharmaceutical formulation. The method was developed using Enable C 18G column (250 × 4.6 mm, 0.5 µm) with a mobile phase consisting of sodium acetate buffer (pH 5.0) and methanol (35:65% v/v) with a flow rate of 1 mL/min. The UV detection was carried out at 234 nm. The retention time for Amlodipine Besylate and Valsartan were found to be 3.146 and 6.543 min respectively. The proposed method was validated for linearity, range, accuracy, precision, robustness, LOD and LOQ. Linearity was observed over a concentration range 0.5-250 µg/ml for amlodipine besylate (r² = 0.9996) and 1-90 µg/ml for Valsartan (r² = 0.9984). The % RSD for Intraday and Interday precision was found to be 0.37 and 0.57 for Amlodipine Besylate and 0.48 and 0.75 for Valsartan. The LOD and LOQ were found to be 0.01 µg/ml, and 0.04 µg/ml for Amlodipine Besylate and LOD and LOQ were found to be 0.04 and 0.14 µg/ml for Valsartan respectively. Amlodipine Besylate and Valsartan were subjected to stress conditions of degradation including acidic, alkaline, oxidative, thermal and photolysis.

Amlodipine Besylate, Valsartan, RP-HPLC, Stability indicating

INTRODUCTION: Amlodipine besylate Fig. 1, chemically designated as 2-[(2-aminoethoxy)-methyl]-4-(2- chlorophenyl) 1,4-dihydro-6-methyl-3,5-pyridine-dicarboxylic acid-3 ethyl-5 methyl ester, is a calcium channel blocker used to treat hypertension and angina. The drug is found to metabolize in the liver, and the produced metabolites are excreted via urine along with some unchanged drug.

FIG. 1: STRUCTURE OF AMLODIPINE BESYLATE

Literature survey reveals various analytical method are reported either alone or combined with other drugs includes UV spectrophotometric ^1-4, Visible spectrophotometric ^5-7, spectrofluorometric ⁸, Titrimetry ⁵, LC-MS ⁹, HPLC ^10-11 in pure drug, pharmaceutical formulations and biological fluids.

Valsartan Fig. 2 Chemically, is (2S)-3-methyl-2-[N- ({4- [2- (2H- 1, 2, 3, 4-tetrazol-5-yl)phenyl] phenyl} methyl) pentanamido] butanoic acid. By blocking the action of angiotensin, valsartan dilates blood vessels and reduces blood pressure. It is an angiotensin receptor blockers that selectively inhibits the binding of angiotensin- II to AT₁, which is found in many tissues such as vascular smooth muscles and the adrenal glands. This effectively inhibits the AT₁-mediated vaso-constrictive and aldosterone-secreting effects of angiotensin-II and results in a decrease in vascular resistance and blood pressure. Valsartan is selective for AT₁ and has virtually no affinity for AT₂. Inhibition of aldosterone secretion may inhibit sodium and water reabsorption in the kidneys while decreasing potassium excretion.

Valsartan is used in the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. It is used in the treatment of heart failure, and it significantly reduces hospitalization for heart failure. It reduces cardiovascular mortality in clinically stable patients with left ventricular failure or left ventricular dysfunction following myocardial infarction. It has an oral bioavailability of 25% and is available in tablet dosage forms. Several analytical methods have been reported for the determination of Valsartan either alone, or in combination with other drugs in pure drug, pharmaceutical dosage forms and biological samples using spectrophotometry ^12-17, HPLC ^18-38, LC-MS ³⁹ and HPTLC ^40-42 methods have been reported for the determination of Valsartan in pharmaceutical dosage forms. The combination of Amlodipine besylate and Valsartan is effective in the treatment of hypertension.

Various analytical methods were reported for simultaneous estimation of Amlodipine besylate and Valsartan in pure drug, pharmaceutical formulations and biological fluids by spectro-photometric ^43-44, HPLC ^45-56 and HPTLC⁵⁷. From the reported RP-HPLC method for the simultaneous estimation of both drugs in pharmaceutical formulation, six methods are stability indicating one but the developed methods have has low linearity range, high flow rate, and mobile phase composition is complex.

Therefore, in the present study, an attempt was made to develop a simple, precise, accurate RP-HPLC method with forced degradation studies for the analysis of Amlodipine besylate and Valsartan in pharmaceutical formulation.

FIG. 2: STRUCTURE OF VALSARTAN

MATERIALS AND METHODS:

Materials and Chemicals: Amlodipine Besylate and Valsartan standard were obtained as a gifted sample from the pharma industry. Amlodipine Besylate and Valsartan tablets (EXFORGE FCT TABLETS) containing Amlodipine besylate 5 mg and Valsartan 80 mg were purchased from the medical store. HPLC grade water was from MERCK India Ltd. HPLC grade methanol was from standard reagent Pvt. Ltd., Hyderabad. Analytical grade acetic acid, sodium acetate, hydrochloric acid, sodium hydroxide, and hydrogen peroxide were from SD Fine chemicals Mumbai, India. Nylon membrane filters 0.2 µm and 0.45 µm were from PALL life sciences Mumbai, India. Ultrasonicator used was from LAB India Ltd Mumbai. pH meter was of Elico LI 120 make. UV Spectrophotometer was of Elico SL 210 model consisted of spectral treats software.

Instrumentation: The chromatographic system used for the method development and validation consisted of Shimadzu HPLC comprising of LC-20AD binary gradient pump, a variable wavelength programmable SPD-20A detector and an SCL 20A system controller. A Rheodyne injector 7725i fitted with a 20 μL loop was used and data were recorded and evaluated by use of LC solutions software version 5.0.

Chromatographic Conditions: Chromatographic analysis was performed on Enable C18 G column (250 × 4.6 mm i.d, 5µ) .The mobile phase consisted of sodium acetate buffer (pH 5.0) and methanol (35:65, % v/v). The flow rate was 1 mL/min, injection volume was 20 µL, and detection was carried out at 234 nm using a UV detector.

Preparations of Amlodipine Besylate and Valsartan Stock Solution: Stock solution of Amlodipine Besylate (1000 µg/ml) and Valsartan (1000 µg/ml) was prepared separately by transferring accurately weighed 50 mg of Amlodipine Besylate and 50 mg of Valsartan into a 50 ml volumetric flask and to it added a 20 ml methanol. The mixture was sonicated for 5 min to dissolve the drug and the solution was diluted up to the mark with methanol. Standard solution Valsartan (100 µg/ml) was prepared by diluting 10 ml of standard stock solution to 100 ml in a volumetric flask with the mobile phase. To prepare a binary mixture of Valsartan and Amlodipine Besylate appropriate volume of standard solution was transferred into a 100 ml volumetric flask and diluted with mobile phase to get a solution containing 100 µg/ml of Valsartan and 10 µg/ml of Amlodipine Besylate.

Analysis of Amlodipine Besylate and Valsartan in Combined Dosage Form: Accurately weighed about twenty tablets and an average weight of tablet was determined. The tablets were transferred into a mortar and triturated to a fine powder form. An a liquate of the powder equivalent to 160 mg of Valsartan and 10 mg of Amlodipine Besylate was transferred into a 100 ml volumetric flask. To it, 20 ml HPLC grade methanol was added and sonicated for 5 min to dissolve the drugs. The content of the flask was kept for 10 min at laboratory temperature and diluted up to mark with HPLC grade methanol this gives a  concentration of Valsartan 1600 µg/ml and Amlodipine Besylate 100 µg/ml. The above solution was filtered through 0.2 µ membrane filter. The 5 ml of the filtrate was transferred into a 100 ml volumetric flask and diluted with mobile phase to get a concentration of 80 µg/ml and 5 µg/ml for Valsartan and Amlodipine Besylate respectively.

Method Validation: The method was validated for accuracy, precision, linearity, specificity, robustness, the limit of detection, the limit of quantitation and system suitability.

Linearity: Linearity was performed by preparing standard solutions of Valsartan and Amlodipine besylate at different concentration levels. Valsartan was prepared in the concentration range of 1-90 µg/mL and 0.5-250 µg/mL for Amlodipine besylate. Twenty micro liters of each concentration from both drug solutions were injected in duplicate into the HPLC system. The response was carried out at 234 nm, and the corresponding chromatograms were recorded from these mean peak areas were calculated. The calibration curve was plotted by taking concentration on x-axis and peak areas on the y-axis for both the drugs.

Accuracy: The accuracy of the method evaluated by standard addition method in which a known amount of standard drug was added to the fixed amount of pre-analyzed tablet solution. Percent recovery of Valsartan and Amlodipine besylate was calculated at three concentration levels of 80%, 100%, and 120%. The solutions were analyzed in triplicate at each level. The percent recovery and % RSD at each level was calculated.

Precision: Precision of the method was evaluated as system precision and method precision. To study the system precision, six replicate standard solutions of Valsartan and Amlodipine Besylate were analyzed. The percent relative standard deviation (% RSD) was calculated for both Valsartan and Amlodipine besylate. Method precision of the analytical method was carried out on six preparations from the tablet formulation, and percentage amount of Valsartan and Amlodipine Besylate in the tablet formulation was calculated. The intraday and interday precision studies were conducted for both Valsartan and Amlodipine Besylate. The mean % assay value, standard deviation and percent relative standard deviation was calculated.

Limit of Detection (LOD) and Limit of Quantitation (LOQ): LOD was measured by serially diluting the standard solutions of Valsartan and Amlodipine Besylate and determining the concentration was the response of sample peaks are three times the noise peak. LOQ was measured by serially diluting the standard solutions of Valsartan and Amlodipine Besylate and determining the concentration was the response of sample peaks are ten times the noise peak.

Robustness: Robustness of the method was determined by making slight changes in the composition of organic phase ± 5%, pH by ± 0.2, flow rate by ± 0.1 ml/min and detection wavelength by ± 2 nm.

Specificity: The specificity of the proposed method was determined against blank and placebo applications. Here mobile phase was used as a blank, and excipients like starch, lactose, magnesium stearate were used as placebo.

Forced Degradation Studies: Different stress conditions were used for the forced degradation studies of the formulation. These were also used to evaluate the specificity of the method. All the samples were diluted with mobile phase and filtered through 0.2 µ membrane filter.

Acidic Conditions: Weighed accurately about twenty tablets and triturated it to a fine powder form. An a liquate of the powder equivalent to 160 mg of Valsartan and 10 mg of Amlodipine besylate was transferred into a 100 ml volumetric flask. To this added a 50 ml of diluent and sonicated for 10 min to dissolve the drug completely. Then 10 ml of 5N HCl was added to it, refluxed for 3 h at 60 ºC, cooled to room temperature, neutralized with 5N NaOH and diluted up to the mark with the diluent. The above sample solution was filtered through 0.2 µ nylon membrane filter. Pipetted 5 ml of the above-filtered sample solution into a 100 ml volumetric flask and volume made up to the mark with diluent.

Alkaline Conditions: Weighed accurately about twenty tablets and triturated it to a fine powder form. An a liquate of the powder equivalent to 160 mg of Valsartan and 10 mg of Amlodipine besylate was transferred into a 100 ml volumetric flask. To this added a 50 ml of diluent and sonicated for 10 min to dissolve the drug completely. Then 10 ml of 2N NaOH was added to it, refluxed for 6 hr at 60 ºC, cooled to room temperature, neutralized with 2N HCl and diluted up to the mark with the diluent. The above sample solution was filtered through a 0.2µ nylon membrane filter. Pipetted 5 ml of the above-filtered sample solution into a 100 ml volumetric flask and volume made up to the mark with diluent.

Oxidative Degradation: Weighed accurately about twenty tablets and triturated it to a fine powder form. An a liquate of the powder equivalent to 160 mg of Valsartan and 10 mg of Amlodipine besylate was transferred into a 100 ml volumetric flask. To this added a 50 ml of diluent and sonicated for 10 min to dissolve the drug completely. Then 5 ml of 3 % hydrogen peroxide was added, refluxed for 10 hr at 60 ºC, then cooled to room temperature and diluted up to the mark with diluents. The above sample solution was filtered through a 0.2µ nylon membrane filter. Pipetted 5 ml of the above-filtered sample solution into a 100 ml volumetric flask and volume made up to the mark with diluent.

Thermal Degradation: Weighed accurately about twenty tablets and triturated it to a fine powder form. The powder sample was subjected to thermal stress at 80 ºC for about 2 days. An a liquate of the powder equivalent to 160 mg of Valsartan and 10 mg of Amlodipine besylate was transferred into a 100 ml volumetric flask.

To this added a 50 ml of diluent and sonicated for 10 min to dissolve the drug completely the diluted up to mark with diluents. The above sample solution was filtered through 0.2 µ nylon membrane filter. Pipetted 5 ml of the above-filtered sample solution into a 100 ml volumetric flask and volume made up to the mark with diluent.

Photolytic Degradation: Weighed accurately about twenty tablets and triturated it to a fine powder form. The powder sample was subjected to UV light in a photostability chamber for about 10 days. An a liquate of the powder equivalent to 100 mg of Valsartan and 10 mg of Amlodipine besylate was transferred into a 100 ml volumetric flask.  To this added a 50 ml of diluent and sonicated for 10 min to dissolve the drug completely the diluted up to mark with diluents.

The above sample solution was filtered through 0.2 µ nylon membrane filter. Pipetted 6 ml of the above-filtered sample solution into a 100 ml volumetric flask and volume made up to the mark with diluent.

RESULTS AND DISCUSSION:

Optimization of Chromatographic Conditions: In the present work an analytical method based on RP-HPLC using UV detection was developed and validated for simultaneous estimation of Valsartan and Amlodipine besylate in pharmaceutical formulation. The selection of analytical conditions was based on the chemical nature of valsartan and Amlodipine besylate. A systematic study of various factors was undertaken by varying one parameter at a time and keeping all other conditions constant for development of the analytical method. Both Valsartan and Amlodipine besylate were soluble in polar solvents; therefore, RP-HPLC was chosen. The selection of stationary phase has been done based on back pressure, resolution, peak shape, theoretical plates and day to day reproducibility in retention time resolution between Valsartan and Amlodipine besylate peaks. After evaluating all these factors Enable C18 G column (250 × 4.6 mm i.d, 5µ) was chosen for the analysis. The selection of buffer was based on the chemical structure of selected drug molecules.

For optimization of the mobile phase, preliminary trials were conducted under isocratic conditions using mobile phases composed of a mixture of solvents like water, methanol, and acetonitrile with or without different buffers in different combinations. A mixture of sodium acetate buffer pH 5.0 and Methanol in the ratio of 30:70 v/v was found to be most suitable of all the combinations since the chromatographic peaks obtained had good system suitability parameters. The Flow rate of mobile phase was optimized based on the resolution between chromatographic peaks and minimal solvent consumption.

The flow rate of mobile phase was changed from 0.5-2 ml/min. It was found from trials that 1 ml/min flow rate was ideal for successful elution of both drugs. For the selection of analytical wavelength standard solutions of both drugs were scanned in the wavelength range of 200-350 nm. A detection wavelength of 234 nm was selected. The chromatogram of the sample was shown in Fig. 3.

FIG. 3: CHROMATOGRAM OF AMLODIPINE BESYLATE AND VALSARTAN

Method Validation: Linearity was studied by preparing standard solutions at different concentration levels. The linearity ranges for Amlodipine Besylate and Valsartan were found to be 0.5-250 µg/mL and 1-90 µg/mL respectively. The linear regression equation for Amlodipine besylate was found to be 3456.5x + 9554.8 with correlation coefficient 0.9996. The linear regression equation for Valsartan was found to be 24099x + 16587 with correlation coefficient 0.9984. The calibration table for Amlodipine Besylate and Valsartan was shown in Table 1 and Table 2 respectively. The calibration curve of Amlodipine Besylate and Valsartan were shown in Fig. 4 and Fig. 5 respectively.

TABLE 1: LINEARITY DATA FOR AMLODIPINE BESYLATE

TABLE 2: LINEARITY DATA FOR VALSARTAN

Accuracy: The percent recovery of Valsartan and Amlodipine besylate was found to be 99.73-100.32% and 100.19-100.45%. This indicates the accuracy of the method. The results are shown in Table 3 and 4.

Precision:

System Precision: The % RSD for Valsartan was found to be 0.361 and for Amlodipine besylate was found to be 1.40 which are within the acceptance criteria of not more than 2.0 indicates the precision of the method. The result was shown in Table 5.

TABLE 3: ACCURACY RESULTS OF VALSARTAN

TABLE 4: ACCURACY RESULTS OF AMLODIPINE BESYLATE

TABLE 5: SYSTEM PRECISION FOR VALSARTAN AND AMLODIPINE BESYLATE

Method Precision: The % RSD for Intraday and Interday precision assay results of six preparations for Valsartan were found to be  0.48 and 0.75 respectively which are within the acceptance criteria of not more than 2.0 indicates the precision of the method. The % RSD for Intraday and Interday precision assay results of six preparations for Amlodipine Besylate was found to be 0.37, and 0.57 respectively which are within the acceptance criteria of not more than 2.0 indicates the precision of the method. The result was shown in Table 6.

Limit of Detection and Limit of Quantitation: The LOD and LOQ were found to be 0.01 μg/mL, and 0.04 μg/mL for Amlodipine Besylate and the LOD and LOQ for Valsartan were 0.04 μg/mL and 0.14 μg/mL respectively.

Robustness: To evaluate the robustness of the developed method, small, deliberate variations in optimized method parameters were made. The effect of change in flow rate, change in pH, change in the composition of mobile phase and detection wavelength on retention time, tailing factor and theoretical plates were studied. The method was found to be unaffected by small changes in flow rate, change in pH, change in the composition of mobile phase and detection wavelength. The results were shown in Table 7 and Table 8.

TABLE 6: METHOD PRECISION FOR VALSARTAN AND AMLODIPINE BESYLATE

TABLE 7: ROBUSTNESS RESULTS FOR AMLODIPINE BESYLATE

TABLE 8: ROBUSTNESS RESULTS FOR VALSARTAN

Specificity: Specificity is the ability to unequivocally assess the analyte in the presence of components that may be expected to be present. Typically, these might include impurities, degradants or matrix. The specificity of an analytical method is its ability to accurately and specifically measure the analyte of interest without interference from blank or placebo. The peak purities of Amlodipine besylate and Valsartan were assessed by comparing the retention times of standard Amlodipine besylate and Valsartan and the sample, and good correlation was obtained between the retention time of the standard and sample. Placebo and blank were injected, and there were no peaks. There is no interference of degradation peaks on drug peaks; hence, the method is specific. The specificity results are shown in Table 9.

TABLE 9: SPECIFICITY RESULTS OF THE METHOD

Analysis of Commercial Formulation: The proposed method was applied for the determination of Amlodipine Besylate and Valsartan in marketed formulations available (EXFORGE FCT TABLETS). The % recovery was found to be 99.60 ± 0.68 and 99.60 ± 0.89 for Amlodipine Besylate and Valsartan respectively in Table 10.

TABLE 10: ANALYSIS OF AMLODIPINE BESYLATE AND VALSARTAN IN COMMERCIAL FORMULATION

*Average of three determinations

Results of Forced Degradation Studies: Under alkaline conditions Amlodipine besylate degraded to 28.64% and Valsartan degraded to 15.86%. In these stress conditions, the retention time of degradation peaks appears at 2.124 min, 9.621 min, and 10.903 min. In acidic conditions, Amlodipine Besylate degraded to 10.44 % and Valsartan degraded to 12.47%. Under these conditions, degradant peak appears at 5.921 min and 13.563 min. In oxidative conditions, Amlodipine Besylate degraded to 26.36% and Valsartan to 19.62%. Although both drugs degraded to a significant extent, but only one minor peak detected at retention times of 2.484 min. In thermal conditions, Amlodipine Besylate degraded to 0.56% and Valsartan degraded to 2.86%. The two degradant peaks appear at retention times of 2.314 min and 2.602 min on the chromatogram. In photolytic conditions, Amlodipine Besylate degraded to 24.88% and Valsartan degraded to 5.74% here also both the drugs degraded to a significant extent, but only one minor peak are detected at retention times of 2.401 min. The degradation chromatograms were shown in from Fig. 6 - Fig. 10. The system suitability parameters of chromatograms were summarized in Table 11.

TABLE 11: FORCED DEGRADATION STUDIES OF VALSARTAN AND AMLODIPINE BESYLATE

CONCLUSION: The proposed method for the simultaneous estimation of Amlodipine Besylate and Valsartan validated as per the ICH guidelines, and it is simple, specific and reliable. The data generated from the forced degradation studies enabled the evaluation of Amlodipine Besylate and Valsartan stability under a variety of ICH recommended conditions. These data are valuable for the safety and potency assessment of a drug product. Furthermore, this simple and rapid RP-HPLC method can also be used successfully for the determination of Amlodipine Besylate and Valsartan in pharmaceutical formulations without any interference from the excipient.

ACKNOWLEDGEMENT: The authors are grateful to Dr. L. Rathaiah, Chairman of Lavu educational society for providing necessary facilities to carry out the above research work.

CONFLICT OF INTEREST: No

REFERENCES:

1. Safila N, Hina Q, Wardha J and Urooj B: Simple UV spectrophotometric assay of Amlodipine. American Journal of Chemistry and Application 2014; 1: 66-69.
2. Swaroopa RK, Swapna A, Padma A, Chaithanya K, Ramalingam P and Teja DHH: A new spectrophotometric method for the estimation of amlodipine besylate and its stress degradation studies. Research Journal of Pharmaceutical, Biological and Chemical Sciences 2011; 2: 470.
3. Nilesh J, Ruchi J, Arti J, Sharad PP and Deepak KJ: spectrophotometric method development and validation for quantitative estimation of amlodipine besylate in bulk drug and their dosage forms by using a hydrotropic agent. Eurasian J Anal Chem 2010; 5: 212-17.
4. Reddy KLL, Sowjanya T, Bandhavi P, Raveendranath T, Desireddy RB and Sowjanya GN: Development and validation of UV spectrophotometric method for estimation of amlodipine besylate in the tablet dosage form. Research Journal of Pharmacy and Technology 2012; 5: 1320-23.
5. Basavaiah K, Chandrashekar U and Nagegowda P: Titrimetric and modified spectrophotometric methods for the determination of amlodipine besylate using bromate-bromide mixture and two dyes. Science Asia 2006; 32: 271-78.
6. Patil VP, Devdhe SJ, Angadi SS, Shelke SD, Jadhav VR, Kawde RV and Kale SH: New ecofriendly validated spectrophotometric method for the estimation of amlodipine besylate in bulk drug using ninhydrin. Asian Journal of Biomedical and Pharmaceutical Sciences 2012; 3: 14-19.
7. Ayşegül G and Cem Y: Colorimetric determination of amlodipine besylate in tablets. Journal of science and Engineering 2006; 9: 1-6.
8. Abdel-Wadood HM, Niveen AM and Ashraf MM: Validated spectrofluorometric methods for determination of amlodipine besylate in tablets. Spectro Chemica Acta 2008: 70(3): 564-70.
9. Hye HY, Tae KK, Bong YL, and Dong HK: Determination of S- and R-Amlodipine in Rat Plasma using LC-MS/MS After Oral Administration of S-Amlodipine and Racemic Amlodipine. Mass Spectrometry Letters 2011; 2(4): 34-42.
10. Meyyanathan SN, Muralidharan S, Rajan S and Gopal K: Suresh BA: A simple sample preparation with HPLC–uv method for estimation of amlodipine from plasma: application to a bioequivalence study. The Open Chemical and Biomedical Methods Journal 2008; 1: 22-27.
11. Mohamed A, Helal UABM, Huda JM, Noor SA and Abbas SA: Development and validation of reversed phase high performance liquid chromatographic method for determination of amlodipine. Tropical Journal of Pharmaceutical Research 2015; 14(4): 663-69.
12. Nataraj KS, Ramakrishnan SVC, Swathi EG, Saigeethika S and Ramanjineyulu K: Simple quantitative method development and validation of Valsartan in pure form and pharmaceutical dosage form by UV- spectroscopy. Int J Pharm & Bio Sci 2011; 1: 67-73.
13. Ramachandran S: Simultaneous spectrophotometric determination of Valsartan and Ezetimibe in pharmaceuticals. Tropical J Pharm Res 2011; 10: 809-15.
14. Mohamed NG: Simultaneous Determination of Amlodipine and Valsartan, Ana Chem Insights 2011; 6; 53-59.
15. Meyyanathan SN: Simultaneous Estimation of Nebivolol Hydrochloride and Valsartan and Nebivolol Hydrochloride and Hydrochlorothiazide in Pharmaceutical Formulations by UV spectrophotometric methods. Int J Pharm Edu Res 2010; 44: 156-59.
16. Rajesh V: Simultaneous Spectrophotometric estimation of Valsartan and Ramipril by the derivative method. Int J Pharm Health Sci 2010; 1: 132-35.
17. Chaudhary AB: Estimation of valsartan and hydrochlorothiazide in pharmaceutical dosage forms by absorption ratio method. Int J Applied Bio and Pharm Techno 2010; 1: 455-64.
18. Maher K, Numan M, Murad A, Raqi S, Nidal J and Abdel NZ: Tablet formulation and development of validated stability-indicating HPLC method for quantification of valsartan and hydrochlorothiazide combination. International Journal of Pharmacy and Pharmaceutical Sciences 2012; 4: 683-87.
19. Elshanawane AA: Stability indicating HPLC method for simultaneous determination of several Angiotensin-II-receptor antagonists in their dosage forms. Pharm Analytica Acta 2012; 3: 1-11.
20. Abdallah OM and Zeid KA: HPLC- fluorescence determination of Valsartan in human volunteers and its application in a bioequivalence study of two Valsartan tablets. Life Sci J 2013; 10: 583-90.
21. Kharoaf M: Tablet formulation and development of validated stability-indicating HPLC method for quantification of Valsartan and hydrochlorothiazide combination. Int J Pharm Pharm Sci 2012; 4: 284-90.
22. Zarghi A et al.: Rapid Quantification of Valsartan in Human Plasma by Liquid Chromatography using a Monolithic Column and a Fluorescence Detection: Application for Pharmacokinetic Studies. Sci Pharm 2008; 76: 439-50.
23. Patnaik A: A new RP-HPLC method for the determination of valsartan in bulk and its pharmaceutical formulations with its indicative stability studies. Int J Pharm Sci 2011; 2: 43-53.
24. Youssef R: Development and Validation of RP-HPLC Method for the Estimation and Separation of Valsartan, Losartan and Irbesartan in Bulk and Pharmaceutical Formulation Int J Pharm Sci Rev Res 2014; 24: 311-14.
25. Nissankararao S: Method development and validation for the estimation of Valsartan in bulk and tablet dosage forms by RP-HPLC. Scholar’s res lib 2013; 5: 206-11.
26. Reddy KNK: Isocratic RP-HPLC method validation of valsartan in pharmaceutical research formulation with stress test stability evaluation of drug substance. J Chem & Pharm Sci 2012; 5: 8-12.
27. Raju VB and Rao AL: Reversed Phase HPLC Analysis of Valsartan in Pharmaceutical Dosage Forms. Int J Chem Environ and Pharm Res, 2011; 2: 56-60.
28. Patro SK: Stability indicating RP-HPLC method for determination of valsartan in pure and pharmaceutical formulation. Euro J Chem 2010; 7: 246-52.
29. Ibrahim MM: Application of an RP-HPLC method for a comparative study on the degradation behavior of two angiotensin II receptor antagonists, valsartan and losartan potassium. Int J Pharm Chem Bio Sci 2015; 5: 417-26.
30. Sarigomula P: Analytical methods development and validation for simultaneous estimation of fluvastatin sodium and valsartan by RP-HPLC technique. Int J Pharm & Ind Res 2013; 3: 152-57.
31. Havaldar FH and Dharmendra VL: Simultaneous estimation of atenolol, hydrochlorothiazide, losartan and valsartan in the pharmaceutical dosage form. Int J pharm & Life Sci 2010; 1: 282-89.
32. Rao KS: Development and validation of specific stability indicating high performance liquid chromatographic method for valsartan. A young pharmacist group of India, 2010; 2: 183-89.
33. Manoranjani M and Bhagyakumar T: RP-HPLC method for the estimation of valsartan in pharmaceutical dosage forms. Int J Sci Inno and Discov 2011; 1: 101-08.
34. Kalpana NK: Method development and validation of stability indicating RP-HPLC method for simultaneous estimation of nebivolol HCl and valsartan in bulk and its pharmaceutical formulations. Am J Adv Drug Deliv 2014; 2: 624-37.
35. Balap AR: Development and validation of RP-HPLC method for simultaneous determination of ramipril and valsartan in its pure and pharmaceutical dosage forms. Int J Uni Pharm & Life Sci 2012; 2: 206-12.
36. Haque MA: Stability indicating RP-HPLC method for the estimation of Valsartan in the pharmaceutical dosage form. IOSR J Pharm 2012; 2: 12-18.
37. Vinzuda DU: RP-HPLC Method for determination of valsartan in the tablet dosage form. Int J Chem Tech Res. 2010; 2: 1461-67.
38. Siddartha B: Analytical method development and validation for simultaneous estimation of nebivolol and valsartan in bulk and pharmaceutical dosage form by RP-HPLC method. Int J Pharm 2014; 4: 340-46.
39. Li H: A liquid chromatography/tandem mass spectrometry method for the simultaneous quantification of valsartan and hydrochlorothiazide in human plasma, J Chromatogr B Analyt Techno Bio Life Sci 2007; 852: 436-42.
40. Jadhav ML: Development and validation of HPTLC method for simultaneous estimation of Valsartan and Hydrochlorothiazide in the tablet dosage form. Int J Pharm & Biosci 2015; 2: 20-25.
41. Gaikwad AV: Simultaneous Estimation of Ramipril & Valsartan in Tablets by HPTLC. Indo-Global J Pharm Sci 2011; 1: 99-12.
42. Ramadan AA: TLC simultaneous determination of valsartan and hydrochlorothiazide in pure form and tablets using butyl-modified aleppo bentonite. Int J Pharm Pharm Sci 2013; 5(3): 762-69.
43. Kul D, Dogan-Topal B, Kutucu T, Uslu B and Ozkan SA: High-performance liquid chromatographic and the first derivative of the ratio spectrophotometric determination of amlodipine and valsartan in their binary mixtures. Journal of AOAC International 2010; 93: 882-90.
44. Mohamed NG: Simultaneous determination of amlodipine and valsartan. Analytical chemistry insights 2011; 6: 53.
45. Devi R: Simultaneous determination and stability evaluation of amlodipine besylate and valsartan in rat plasma by RP-HPLC method. Int J Biopharm 2010; 1: 31-38.
46. Maheshwari N: Validated reverse phase high-performance liquid Chromatography method for simultaneous estimation of Valsartan Potassium and Amlodipine Besylate in the tablet dosage form. Int J drug Div & Res 2013; 5(3): 237-44.
47. El-Gizawy SM: Development and validation of HPLC method for simultaneous determination of amlodipine, valsartan, hydrochlorothiazide in dosage form and spiked human plasma. Am J Ana Chem 2012; 3: 422-30.
48. Mhaske RA: RP-HPLC method for simultaneous determination of amlodipine besylate, valsartan, telmisartan, hydrochlorothiazide and chlorthalidone: application to commercially available drug products. Int J Pharm Sci Res 2012; 3: 141-49.
49. Prasad CVN, Santhosh KCh and Ramulu SJ: A stability indicating RP-HPLC method with shorter runtime for Simultaneous estimation of valsartan and amlodipine from their Combination drug product. International Journal of Research In Pharmacy And Chemistry 2011; 1: 102-10.
50. Chitlange SS, Kiran B and DM Sakarkar: Stability indicating RP- HPLC method for simultaneous estimation of valsartan and amlodipine in the capsule formulation. Asian J. Research Chem 2008; 1: 15-18.
51. Rama JVE, Gopichand I, Venkatasubramanian J, Sudhakar RV and Sree RJ: New stability indicating a method for quantification of impurities in amlodipine and valsartan tablets by validated HPLC. ISRN Medicinal Chemistry 2013.
52. Tadeusz I, Anna G, Paulina M and Ewelina R: New HPLC method with experimental design and fluorescence detection for the analytical study of antihypertensive mixture, amlodipine and valsartan. American Journal of Analytical Chemistry 2013; 4: 17-23.
53. Samya M. ElG, Osama HA, Mahmoud AO, Sayed MD and Ahmed MAM: Development and validation of HPLC method for simultaneous determination of amlodipine, valsartan, hydrochlorothiazide in dosage form and spiked human plasma. American Journal of Analytical Chemistry 2012; 3: 422-30.
54. Snehal BP, Bharat GC, Munish KB and Ashok BP: Stability indicating RP-HPLC method for Simultaneous determination of valsartan and Amlodipine from their combination drug product. International Journal of ChemTech Research 2009; 1: 1257-67.
55. Jothieswari D, Anada KK, Vijaya SD, Vijaya KB, Priya D and Stephen RB: Validated RP-HPLC method for the simultaneous determination of  Amlodipine Besylate, Valsartan and Hydrochlorothiazide in bulk and pharmaceutical formulation. Journal of Pharmaceutical and Biomedical Sciences 2010; 5: 1-7.
56. Rahul RN, Sagar SJ, Varsha M, Nalini S, Surendra N KVC and Sathish J: Stability indicating RP-HPLC method for simultaneous determination of amlodipine besylate and valsartan combination in bulk and commercial dosage forms. Asian Journal of Pharmacy and Life Sciences 2012; 2: 280-90.
57. Dhaneshwar SR, Patre NG and Mahadik MV: Validated TLC method for simultaneous quantitation of amlodipine besylate and valsartan in bulk drug and formulation. Chromatographia 2009; 69: 157-61.
    

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    How to cite this article:

    Kumar TH and Asha CH: New validated stability indicating RP-HPLC method for simultaneous estimation of amlodipine besylate and valsartan in pharmaceutical formulation. Int J Pharm Sci & Res 2019; 10(5): 2633-43. doi: 10.13040/IJPSR.0975-8232.10(5).2633-43.

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