Optimization of RP-HPLC Assay for Pharmaceutical Analysis of Clopidogrel

Gujar et al: Formulation and Evaluation of Gastroretentive Nanopaticles of Repaglinide 2371 International Journal of Pharmaceutical Sciences and Nanotechnology Volume 7 Issue 1 January March 2014 Research Paper IJPSN-8-4-13-HOUSHEH Optimization of RP-HPLC Assay for Pharmaceutical Analysis of Clopidogrel Samer Housheh 1 *, Ali Daoud 1, Saleh Trefi 1, Mohammad Haroun 2 and M. Fawaz Chehna 1 a Department of Quality Control and Pharmaceutical Chemistry, University of Aleppo, Syrian Arab Republic and b Department of Quality Control and Pharmaceutical Chemistry, University of Tishreen, Syrian Arab Republic. Received August 4, 2013; accepted September 19, 2013 ABSTRACT An accurate, sensitive, precise and stability-indicating reversed phase high performance liquid chromatographic (RP-HPLC) method for the analysis of clopidogrel bisulfate was developed and validated. The chromatographic conditions comprised of a reversible phase C 18 column (250 4.6 mm, 5 µm) with a mobile phase consisting of a mixture of 50 mm potassium di-hydrogen phosphate and acetonitrile in the ratio of 75:25 at ph 3.0 adjusted with phosphoric acid. The flow rate was 1ml/min, the detection was carried out at 247 nm and the retention time of KEYWORDS: RP-HPLC; Clopidogrel; assay validation; degradation; stability indicating. clopidogrel was 6.5 min. Clopidogrel was subjected to acid and alkali hydrolysis, oxidation and photodegradation. The method was validated for accuracy, precision and robustness. The results indicate that the drugs are susceptible to degradation in different conditions. All the peaks of degraded products were resolved from the active pharmaceutical ingredient with significant different retention times. As the method could effectively separate the drug from its degradation products, it could be employed as a stability-indicating method. Introduction Clopidogrel bisulfate (CLP) is a widely used antiplatelet drug worldwide. It is chemically known as methyl(s)-2-chloro phenyl (4,5,6,7-tetrahydro thieol [3,2- c] pyridine-5yl) acetate bisulphate (Fig.1). Clopidogrel is an anti platelet aggregation agent which selectively inhibits the binding of adenosine diphosphate (ADP) to its platelet receptor and blocks the subsequent ADPmediated activation of the glycol protein GPIIb/IIIa complex, thereby inhibiting platelet aggregation (Jarvis and Simpson, 2000). It is used worldwide for chronic prevention of atherothrombotic events such as myocardial infarction, stroke, peripheral arterial disease, acute coronary syndrome, and cardio-vascular death (Bertand et al., 2000; CAPRIE Steering Committee, 1996; Yusuf et al., 2001). Fig. 1. Chemical structure of clopidogrel. Although the majority of the drug is hydrolyzed by esterase to an inactive carboxylic acid metabolite, the full anti-aggregating activity of the drug is achieved by biotransformation to 2-oxo-Clopidogrel by cytochrome P450-1A. This intermediate metabolite is hydrolyzed, and it generates an active form which reacts as thiol reagent with the ADP receptor on platelets thus preventing the binding of ADP (Pereillo et al., 2002). The International Conference ofharmonization (ICH) guidelines require that analysis of stability test samples should be done by using stability indicating assay methods developed and validated after stress testing on the drug under a variety of conditions including hydrolysis across a wide range of ph values, oxidation, photolysis and thermal degradation. Therefore, there is a necessity to subject the drug to stress studies and establish stability indicating assay methods based on analysis of stressed samples (Shah et al., 2008). The United States Pharmacopoeia recommended a reverse phase HPLC method with UV detection at 220 nm for determination of clopidogrel bisulphate in tablets. Literature survey reveals that there are different types of assay methods for the determination of clopidogrel in pharmaceutical dosage forms. These analytical methods include chemometric (Rajput et al., 2008), spectrophotometric (Chaudhari et al., 2010), TLC (Antic et al., 2007), HPLC (Rashmin et al., 2008), HPTLC (Himani et al., 2003), LC-MS (Mitakos and Panderi, 2002), gas chromatographic (Kample and Venkatachalan, 2005) and voltametric methods (Dermis and Aydogan, 2010). The aim of the presented work is to develop simple, accurate, and stability-indicating method for the determination of clopidogrel in the presence of its 2371

2372 Int J Pharm Sci Nanotech Vol 7; Issue 1 January March 2014 degradation products after performing stress studies under a variety of ICH recommended test conditions. The presented study only deals with method development and validation. Materials and Methods Drugs and chemicals Working standard of Clopidogrel (Purity 99.81%) was provided as a gift from Al-Razi Laboratories, Syria and used without further purification. All the other reagents used were of HPLC grade: Methanol (Sharlau, Spain), Acetonitrile, Tri ethanolamine (TEA), Hydrochloric acid (Surechem, England), Sodium hydroxide, Hydrogen peroxide, Filters 0.45µm. Water for HPLC was distilled from glass apparatus. The HPLC instrument used was SHIMADZU system equipped with a UV detector. Standard Preparation 100 ml of methanol. The resultant solutions were appropriately diluted to obtain final concentration in the range 25-125 µg/ml and chromatograms were run. The analysis was repeated in triplicate. Method development and optimization of chromatographic conditions Selection of Detection Wavelength: Clopidogrel bisulfate solution was prepared in diluent at a concentration of 100 μg/ml and scanned in UV-Visible spectrophotometer. Column selection: The objective of the chromatographic separation was to separate Clopidogrel from its degradation products. Initial trials were conducted using two different stationary phases: Reversed phase C18 column, 250 4.6 mm. Reversed phase C8 column, 250 4.6 mm. Mobile phase selection: A lot of mobile phases with each column have been tried to get the optimum resolution: With column C18 250 4.6 mm acid) Flow rate 1ml/min. acid) Flow rate 1.5ml/min. Methanol: Water (80:20) ph=3 (phosphoric acid) Flow rate-1ml/min. acid) Flow rate-1ml/min. With Column C8 250 4.6mm Methanol (100%) 0.1 % TEA, Flow rate 1ml/min. acid) Flow rate 1ml/min. acid) Flow rate 1.5ml/min. Stress degradation of clopidogrel bisulphate: Different kinds of stress conditions were employed on Clopidogrel bisulfate based on the guidance available from ICH Stability Guideline. The details of the stress conditions applied were as follow: Preparation of acid and base induced degradation product 100 ml of methanol. The drug was subjected to accelerated degradation under acidic and basic conditions by refluxing with 1N HCl and 1N NaOH, respectively, at 70 C for a period of 3 and 1hr, respectively. The accelerated degradation in acidic and basic media was performed in the dark in order to exclude the possible degradation effect of light on the drug. The resultant solutions were appropriately diluted and chromatograms were run (Agrawal et al., 2003). Preparation of hydrogen peroxide induced degradation product 100 ml of methanol. Subsequently, 10 ml of hydrogen peroxide 30.0% v/v was added and the solution was heated in boiling water bath for 1 hr till the removal of excess hydrogen peroxide. The resultant solutions were appropriately diluted and chromatograms were run (Agrawal et al., 2003). Photochemical degradation product 100 ml of methanol. The photochemical stability of the drug was also studied by exposing the drug solution to direct sunlight for 12 h. The resultant solutions were appropriately diluted and chromatograms were run (Agrawal et al., 2003). Results and Discussion Selection of detection wavelength As noticed in Figure 2, Clopidogrel bisulfate had λ maximum at around 247 nm. Hence detection at 247±2 nm was selected for method development purpose. HPLC analysis The chromatographic conditions were optimized with a view to develop a validated method for the determination of CLP and a stability indicating assay method. As showed in Figure 3, the experimental studies revealed that the column, RP-C18 (250 4.6 mm, 5µ) was the most suitable, since it produced the best chromatographic performance and acceptable peak characteristics including high resolution and very good sensitivity with no interferes, impurities, or tailing in the peak. The Chromatographic conditions finally comprised of a mobile phase consisting of a mixture of 50mM Potassium di-hydrogen Phosphate and Acetonitrile (75:25 v/v) at ph 3.0 adjusted with phosphoric acid with a flow rate of 1ml/min and detection was carried out at 247 nm.

Housheh et al: Optimization of RP-HPLC Assay for Pharmaceutical Analysis of Clopidogrel 2373 Fig. 2. Wave length selection. Fig. 3. HPLC chromatogram of clopidogrel.

2374 Int J Pharm Sci Nanotech Vol 7; Issue 1 January March 2014 Analytical method validation Method validation was performed under a variety of ICH and United States Pharmacopeia 30 recommended test conditions. Linearity: Five standard solutions of CLP were prepared with the concentrations (25, 50, 75, 100 and 125 µg/ml), each solution was injected six times in HPLC. Figure 4 shows the linearity of CLP with a correlation coefficient of 0.9996. Range: Linearity, precision and accuracy were conformed in the interval (25, 50, 75, 100 and 125 µg/ml) for CLP. Accuracy: Concentrations of 25, 50, 75, 100, and 125 µ g/mlhave been used to study the accuracy of CLP (Table 1). Results indicate that the individual recovery of Clopidogrel ranges from 98.57% to 101.298% with mean recovery of 100.085% and % RSD of 0.716%. The recovery of the Clopidogrel by proposed method is satisfactory as %RSD is not more than +2.0% and mean recovery between 98.0 102.0%. Precision: Repeatability. The solution 75 µg/ml has been injected ten times. Standard deviation and relative standard deviation of the response (peak area) have been calculated and the results were illustrated in Table 2.The RSD% for repeatability of sample preparation is 0.72; this shows that the precision of the method is satisfactory as RSD% is not more than +2.0%. Fig. 4. Clopidogrel linearity. TABLE 1 Accuracy of clopidogrel assay. Conc. µg/ml Area Calc. Area Calc. Conc. Recovery % AVR SD RSD % 25 8867657 8867657 24.816 99.266 25 8955834 8955834 25.063 100.253 99.624 0.546 0.548 25 8875463 8875463 24.838 99.353 50 17864776 17864776 49.995 99.99 50 18098392 18098392 50.649 101.298 100.275 0.914 0.912 50 17783645 17783645 49.768 99.536 75 26987832 26987832 75.526 100.702 75 26871873 26871873 75.202 100.269 100.557 0.249 0.248 75 26987644 26987644 75.526 100.701 100 35974665 35974665 100.676 100.676 100 35564738 35564738 99.529 99.529 100.41 0.782 0.779 100 36098876 36098876 101.024 101.024 125 44372642 44372642 124.178 99.342 125 44987837 44987837 125.9 100.72 99.545 1.088 1.093 125 44028337 44028337 123.215 98.572 TABLE 2 Repeatability of clopidogrel. Conc. µg/ml Area AVR STDV RSD % 75 25766475 75 25574683 75 25987644 75 26188743 75 26037621 25891343 187397.7 0.723785 75 25897834 75 25694872 75 25897564 75 25976654

Housheh et al: Optimization of RP-HPLC Assay for Pharmaceutical Analysis of Clopidogrel 2375 Intermediate Precision. The RSD% for intermediate precision of the sample preparation is 1.77. This shows that the intermediate Precision of the method is satisfactory as RSD% is not more than +2.0%. (Table 3) TABLE 3 Intermediate precision of clopidogrel. No. of Injection Conc. µg/ml Area Solution A 1 75 25766475 2 75 25574683 3 75 25987644 4 75 26188743 5 75 26037621 6 75 25897834 Solution B 25694872 1 75 26897564 2 75 26976654 3 75 25874345 4 75 25789647 5 75 26543619 6 75 Mean 26102475.08 STDV 463698.67 RSD% 1.77 Robustness: The method robustness and ruggedness were determined by analyzing the same sample at normal operating conditions and also by changing some operating analytical conditions such as flow rate and wave length detection. As illustrated in Table (4) and Table (5), the slight changes in the method parameter do not affect the analysis. TABLE 4 Flow rate modification of clopidogrel. No. of Injection Modification of Flow Rate Retention time (min) Flow Rate = 0.8 ml min Flow Rate = 1.2 ml min Rt of unchanged flow rate Flow Rate= 1 ml min 1 8.23 4.76 6.55 2 8.27 4.67 6.65 3 8.25 4.72 6.52 4 8.22 4.78 6.59 5 8.24 4.73 6.57 6 8.26 4.69 6.62 AVR 8.245 4.725 6.583 SD 0.018 0.041 0.047 RSD% 0.226 0.875 0.716 TABLE 5 Wave length modification of clopidogrel. No. of Injection Modification of Wave Length Peak Area of unchanged Peak Area wave length λ=247 nm λ=243 nm λ=245 nm 1 17375689 16965765 17864776 2 17248556 16874653 17898392 3 17284738 16985742 17783645 4 17493280 16746583 17536452 5 17237532 17098542 17555342 6 17465223 16893874 17636647 AVR 17350836.33 16927526.5 17712542.33 SD 111049.80 118967.37 157639.22 RSD% 0.64 0.702 0.889 LOD and LOQ: The calculated LOD (Limit of Detection) and LOQ (Limit of Quantification) were 11.26 µg/ml and 34.12 µg/ml respectively. Stability indicating property The chromatogram of no stress treatment sample (as control) indicated no additional peak (Fig. 3). A standard solution of CLP was exposed to different kinds of degradation (acid, base, oxidation, sunlight) and injected into HPLC. The chromatogram of acid degraded sample presented one additional peak with retention time of 3.75 min, but it s well resolved from the peak of CLP with a significant difference in the retention time between the two peaks (Fig.5). The chromatogram of alkali degraded sample also showed one additional peak at retention times of 3.65 min and it s well resolved from the peak of CLP (Fig. 6). The chromatogram of H2O2 degraded sample illustrated many peaks at retention time between 1-2.5 min and they are well resolved from the peak of CLP (Fig.7). There are small peaks at 4.4 min and 5.04 min in photo degraded sample of CLP (Figure 8). As presented in all the chromatograms, the peak of CLP is completely separated from the peaks of degradation products. Fig. 5. Acidic degradation of clopidogrel. Fig. 6. Basic degradation of clopidogrel.

2376 Int J Pharm Sci Nanotech Vol 7; Issue 1 January March 2014 Fig. 7. Degradation of clopidogrel under H2O2. Fig. 8. Photodegradation of clopidogrel. System Suitability: System suitability parameters were calculated and illustrated in Table 6. TABLE 6 Clopidogrel system suitability. Acceptance Criteria Value Result RSD% of Area 1 0.894 Pass RSD% of RT 1 0.705 Pass Assymetry 0.8-1.5 1.15 Pass Plate Effe. 50 % > 2000 10900.8 Pass Conclusions The HPLC described in this report appears rapid, precise, accurate and stability-indicating for the analysis of clopidogrel bisulfate in raw material and in pharmaceutical dosage forms. As the method separates the drug from its degradation products, under all stress conditions using HCl, NaOH, H2O2 and sunlight, it can be employed as a stability indicating one. Acknowledgements The authors acknowledge the financial support received from the University of Aleppo and would like to thank Mr. Ayham Aljghami for his lingual help. References Agrawal H, Kaul N, Paradkar AR and Mahadik KR (2003). Stability indicating HPTLC determination of Clopidogrel bisulphate as bulk drug and in pharmaceutical dosage form. Talanta 61: 581 589. Antic D, Filipic S and Agbaba D (2007). A simple and sensitive TLC method for determination of Clopidogrel and its impurity SR 26334 in pharmaceutical product. ActaChromatogr 18: 199 206. Bertand ME, Rupprecht HJ, Urban P and Gershlick AH (2000). Double-blind study of the safety of Clopidogrel with and without a loading dose in combination with aspirin compared with ticlopidine in combination with aspirin after coronary stenting: the Clopidogrel Aspirin Stent International Cooperative Study (CLASSICS). Circulation 102: 624 629. CAPRIE Steering Committee (1996). A randomised, blinded, trial of Clopidogrel versus aspirin in patients at risk of ischaemic events. Lancet348: 1329 1339. Chaudhari PB, Pawar PD and Narkhede KP (2010). Stability indicating spectrophotometric method for determination and validation of Clopidogrel bisulfate in tablet dosage form. Int J Res Ayur & Pharm 1(2): 418 423. Dermis S and Aydogan E (2010). Electrochemical study of Clopidogrel and its determination using differential pulse voltammetry in bulk drug and pharmaceutical preparations. Pharmazie 65(3): 175 181. Himani A, Neeraj K, Paradkar AR and Mahadik KR (2003). Stability indicating HPTLC determination of method for Clopidogrel bisulfate as bulk drug and in pharmaceutical dosage form. J Pharm & Biomed Anal 61: 581 589. International Conference on Harmonization (ICH) of Technical Requirements for the Registration of Pharmaceuticals for Human Use. Note for guidance on stability testing: stability testing of new drug substances and products (CPMP/ICH/2736/99), ICH Topic Q1 A (R2) Stability Testing of new Drug Substances and Products. International Conference on Harmonization (ICH) of Technical Requirements for the Registration of Pharmaceuticals for Human Use (1996). Validation of Analytical Procedures: Methodology. ICH-Q2B, Geneva, CPMP/ICH/281/95. Jarvis B and Simpson K (2000). Clopidogrel: a review of its use in the prevention of atherothrombosis. Drugs 60:347 377. Kample NS and Venkatachalan A (2005). Estimation of Clopidogrel from tablet dosage form by gas chromatography method. Indian J Pharm Sci 67: 128 129. Mitakos A and Panderi I (2002). A validated LC method for the determination of clopidogrel in pharmaceutical preparations. J Pharm Biomed Anal 28(3-4): 431 438. Pereillo JM, Maftouh M, Andrieu A, Uzabiaga MF, Fedeli O, Savi P, Pascal M, Herbert JM, Maffarand JP and Picard C (2002). Structure and stereochemistry of the active metabolite of clopidogrel. Drug Metab. Dispos 30:1288 1295. Rajput SJ, George RK and Ruikar Deepthi B (2008). Chemometric simultaneous estimation of clopidogrel bisulfate and aspirin from combined dosage form. Indian J Pharm Sci 70: 450 454. Rashmin BP, Madhira BS, Mrunali R and Kashyap PB (2008). Simultaneous estimation of acetylsalicylic acid and clopidogrel bisulfate in pure powder and tablet formulations by HPLC and HPTLC. J AOAC Int 91(4): 750 755. Shah CR, Suhagia BN, Shah NJ, Patel DR and Patel NM (2008). Stability indicating simultaneous HPTLC method for olanzapine and fluoxetine in combined tablet dosage form. Indian J Pharm Sci 70(2): 251 255. Yusuf S, Zhao F, Mehta SR, Chrolavicius S, Tognoni G and FoxKK (2001). Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation. N Engl J Med 345:494 502. Address correspondence to:samer Housheh, Department of Quality Control and Pharmaceutical Chemistry, Faculty of Pharmacy, University of Aleppo, Syrian Arab Republic. Tel.: +963-944-916205 E-mail: samerhousheh@hotmail.com