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Tropical Journal of Pharmaceutical Research, Vol. 9, No. 5, September-October, 2010, pp. 499-503 Research Article Spectrophotometric Determination of Cilostazol in Tablet Dosage Form Pawan Kumar Basniwal1*, Vinesh Kumar1, Prabhat Kumar Shrivastava2 and Deepti Jain3 1LBS College of Pharmacy, Tilak Nagar, Jaipur –302004, Rajasthan, 2Department of Pharmaceutics, Banaras Hindu University, Banaras, UP, 3School of Pharmaceutical Sciences, Rajiv Gandhi Technical University, Bhopal (MP), India *Corresponding author: E-mail: pawanbasniwal@gmail.com; Tel: +91-9414788171 (mob). Received: 8 January 2010 Revised accepted: 21 July 2010 Code Number: pr10060 Abstract Purpose: To develop simple, rapid and selective spectrophotometric
methods for the determination of cilostazol in tablet dosage form. Keywords: Cilostazol tablets, UV spectrophotometry, Linear regression equation, Standard absorptivity. INTRODUCTION Cilostazol, whose chemical name is 6-[4-(1cyclohexyl-1H-tetrazol-5-y1) butoxy]-3, 4dihydro-2 (1H) – quinolinone (see Fig 1), is a quinolinone derivative that inhibits cellular phosphodiesterase III, and is used for the inhibition of platelet aggregation and as a vasodilator [1-4]. The literature reveals that chromatographic methods are employed in the determination of cilostazol in tablet dosage form and human plasma and, to the best of our knowledge, no spectrophotometric method has yet been reported for this compound in tablet form [56]. However, the degradation profile and RP-HPLC analysis of cilostazol in tablet dosage form has been reported [7]. Compared to chromatographic methods, spectrophotometric methods are suitable for routine analysis because it is economic, rapid, simple, maintenance-free, and show comparable accuracy and precision with HPLC methods. Therefore, the object of the present work was to develop spectrophotometric methods for the determination of cilostazol in tablet form. EXPERIMENTAL Instruments, reagents and chemicals Ultraviolet spectrophotometer (1700 series, Shimadzu) and UV-VIS double beam spectrophotometer 2201 (Systronics) with 1 cm matched quartz cells were used for the measurement of absorbance. Shimadzu-Ax200 electronic balance was used for weighing the samples, and class “A” volumetric glassware were used. Working standard (WS) of cilostazol was a gift from IPCA Laboratories Ltd, Ratlam, MP, India, while Pletoz®50 tablets (cilostazol tablets 50 mg) manufactured by Hetero Drugs Ltd, Hyderabad were procured from a local pharmacy. Methanol AR grade (Merck, India) and distilled water were used for analytical work. Linear regression equation methodStock A (500 µg/ml cilostazol) was prepared from accurately weighed 50 mg cilostazol WS in 50 % aqueous methanol. It was diluted with the solvent to produce Stock B (50 µg/ml); aliquots of Stock B were further diluted to give concentrations of 5, 10, 15, 20 and 25 µg/ml of cilostazol, respectively. These dilutions were scanned from 300 to 200 nm against 50 % aqueous methanol as blank, and their absorbances observed at 258.2 nm. Standard absorptivity methodFive dilutions of cilostazol were prepared in triplicate and their absorbances were observed at 258.2 nm. From the above observations, the standard absorptivity, A (1%, 1cm), and molar extinction coefficient were calculated. Validation of methodsAs per ICH guidelines [8-9], six dilutions in triplicate were used to validate both methods for linearity, accuracy (by recovery studiesstandard addition to pre-analysed samples), repeatability (within day), intermediate precision (days, analyst and instrument variation) and robustness (methanol variation: 45, 50 and 55 %), and statistical parameters were calculated for them. Quantitative determinationTwenty cilostazol tablets were weighed and finely powdered; a quantity equivalent to 50 mg of cilostazol was dissolved in 100 ml of 50 % aqueous methanol and filtered through Whatman filter paper no. 41 to give Stock P. Stock P was diluted to obtain Stock Q (50 µg/ml). Aliquots of Stock Q were diluted to obtain sample concentrations in the range of linearity. The absorbance values of these sample solutions were observed in a multipoint calibration curve of quantitative mode at the selected wavelength (258.2 nm) to obtain test sample concentration. RESULTSThe linear regression equation obtained from analyzing standard solutions of cilostazol is shown in Eq 1. ABC = 0.2069C -0.204 .................................... (1) It showed an r2 = 0.9999 where ABC = absorbance, C = concentration (µg/ml), and r2= correlation coefficient. The standard absorptivity, A (1%, 1cm), and molar extinction coefficient (ε) for cilostazol were 420.23 dlg-1cm-1 and 15527.5 1 Mol--1 cm-1 , respectively (see Table 1). These developed methods were validated for various parameters, viz, accuracy, precision (repeatability, intermediate precision for days, instrument and analysts) and robustness. Statistical analysis (SD, CV, SEx and SEσ) for validation parameters are summarized in Table 2. These parameters were less than one. Thus, these parameters show the suitability of the methods. The validated methods were applied to determine cilostazol in tablet dosage form, and the results were 101.23 % (SD = 0.611) by LRE method, and 99.96 % (SD = 0.592) by SA method. Mean of standard deviation (SEx) and standard error of standard deviation (SEσ) were far less than acceptable limits (see Table 3). Value of coefficient of variance for robustness was within acceptable limits. DISCUSSIONThe linear regression equation and standard absorptivity methods have been validated as per ICH guidelines, and results of validation parameters were within acceptable limits. Cilostazol was estimated by LRE and SA methods in tablet dosage form with standard deviation of 0.611 and 0.592, respectively. On comparing the two methods using the Ftest, the calculated value of F (1.065) was substantially less than the theoretical value at 99 % confidence value; therefore, the methods have comparable precision. Impurities or any other interfering substances with λ max close to that of cilostazol (258.2 nm) would adversely affect the accuracy of the developed methods.. Further study on possible interfering substances will need to be carried out. CONCLUSIONThe developed methods for cilostazol are simple, rapid and economical with acceptable accuracy, precision, reproducibility and are robust to slight variations in experimental conditions. Thus, the validated methods may be used for routine analysis of cilostazol as the bulk drug and in tablets and other dosage forms where excipients will not interfere spectrally. REFERENCES
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