1 Brzilin Journl of Phrmceuticl Sciences vol. 49, n. 2, pr./jun., 2013 Article RP-HPLC method development nd vlidtion for estimtion of rivroxbn in phrmceuticl dosge forms Mustf Çelebier, Tub Reçber, Engin Koçk, Scide Altınöz * Deprtment of Anlyticl Chemistry, Fculty of Phrmcy, Hcettepe University, Turkey Rivroxbn, n nti-clotting mediction, cts t crucil point in the blood-clotting process nd stops the formtion of blood clots. In this study, RP-HPLC method ws developed for the determintion of rivroxbn in tblets (Xrelto (10 mg)). Phenomenex Lun 5 µm C Å LC Column (250 x 4.6 mm) ws used t 40 o C. Isocrtic elution ws performed with ACN:Wter (55:45 v/v) mixture. The flow rte ws 1.2 ml min -1 nd UV detection ws t 249 nm. Internl stndrd (Cffeine) nd rivroxbn were eluted within 2.21 nd 3.37 minutes, respectively. The developed method ws vlidted ccording to the ICH guidelines nd found to be liner within the rnge µg ml -1. The method ws ccurte, precise, robust nd rpid. Thus, it ws pplied successfully for the qulity control ssy of rivroxbn in tblet dosge form. Uniterms: HPLC. Rivroxbn. Vlidtion. System suitbility. Stbility-indicting. Phrmceuticl dosge form. Rivroxbn, fármco nticogulnte, tu em um ponto crucil no processo de cogulção do sngue e impede formção de coágulos snguíneos. Neste estudo, desenvolveu-se método de RP-HPLC pr determinção de rivroxbn em comprimidos (Xrelto (10 mg)). Utilizou-se colun LC (250 x 4,6 mm) Phenomenex Lun C18 5 mm 100 Å 40 o C. Relizou-se eluição isocrátic com ACN: águ (55:45 v/v). O fluxo foi de 1,2 ml min-1 e detecção de UV foi 249 nm. Pdrão interno (cfeín) e rivroxbn eluírm em 2,21 e 3,37 minutos, respectivmente. O método desenvolvido foi vliddo de cordo com s diretrizes do ICH e mostrou-se liner n fix 0,005-40,0 mg ml -1. O método foi exto, preciso, robusto e rápido. Assim, foi plicdo com êxito pr o ensio de controle de qulidde d Rivroxbn n form de comprimidos. Unitermos: HPLC. Rivroxbn. Vlidção. Adequção do sistem. Indicdor de estbilidde. Form frmcêutic. INTRODUCTION Anticogulnts re given to prevent the blood from clotting or prevent to existing clots from getting lrger. Clots cn block the blood flow to the hert muscle or block the blood flow to the brin. These cuse hert ttck or stroke. Rivroxbn (RIV), n orl oxzolidinone-bsed nticogulnt, is potent, selective direct inhibitor of fctor X tht is used in the prevention of venous thromboembolism in dult ptients fter totl hip replcement or totl knee replcement surgery. RIV (Figure 1) is smll molecule (moleculr mss: 436 g mol -1 ) tht is lmost insoluble in wter nd exhibits high plsm protein binding (92 95%) in humns, with serum lbumin being the min binding component. The potency of fctor X inhibition occurs primrily *Correspondence: S. Altınöz. Hcettepe University, Fculty of Phrmcy, Deprtment of Anlyticl Chemistry Ankr- Turkey. E-mil: FIGURE 1 - Chemicl structure of rivroxbn.
2 360 M. Çelebier, T. Reçber, E. Koçk, S. Altınöz s result of RIV binding with high selectivity to the S1 nd S4 pockets of the serine endopeptidse (Duggn et l., 2009). Inhibition of fctor X interrupts the intrinsic nd extrinsic pthwy of the blood cogultion cscde, inhibiting both thrombin formtion nd development of thrombi. RIV does not inhibit thrombin (ctivted Fctor II), nd hs no effects on pltelets hve been demonstrted (Pezborn et l., 2007; Terry et l., 2009). The RIV ws pproved for mrketing by Helth Cnd nd Europen Commission in In the literture, there is n HPLC- MS method for the determintion of RIV in humn plsm for phrmcokinetic studies (Rohde, 2008). However, there is no method reported for the quntifiction of RIV in phrmceuticl dosge forms. It is well known tht qulity control is n importnt tsk in the phrmceuticl industry. The term qulity control refers to the sum of ll procedures undertken to ensure the identity nd purity of prticulr phrmceuticl (WHO, 2010). Qulity control mesurements include stbility testing of the drug formultion, dissolution testing nd nlysis of rw mterils nd synthesis products. A phrmceuticl compny usully hs to mesure lrge number of qulity control smples nd HPLC is unique technique for the nlysis of wide vriety of smples (Dong, 2005). In this study, it ws imed to develop n ccurte, precise, robust, rpid nd selective HPLC method for determintion of RIV in tblet dosge forms. The stbility of RIV ws evluted nd lso forced degrdtion procedure ws pplied under stress conditions like high temperture, cidic-lkli conditions, nd irrdition with UV light. The developed method ws fully vlidted ccording to the ICH (ICH, 2005) guidelines nd observed tht it ws cpble of determining RIV in the presence of forced degrdtion products. Therefore, it could be concluded tht this method could be proposed for the qulity control process of RIV in phrmceuticl industry. MATERIAL AND METHODS Chemicls nd regents RIV working stndrd ws supplied from Refik Sydm Hıfzısıhh Ntionl Public Helth Agency. The tested phrmceuticl formultions (Xrelto 10 mg, (pproved in Cnd, 2008) were procured from Byer Turkey. Acetonitrile (ACN) ws nlyticl grde nd purchsed from Merck. Apprtus nd Chromtogrphic conditions HPLC nlyses were performed on Shimdzu UFLC system. Seprtions were crried on Phenomenex Lun 5 µm C Å LC Column (250 x 4.6 mm). The column temperture ws set t 40 o C nd the flow rte ws 1.2 ml min -1 while using isocrtic elution with ACN:Wter (55:45 v/v) mixture. Injection volume ws 5 μl nd UV detection ws performed t 249 nm. Pek identity ws confirmed by retention time comprison. Preprtion of stndrd solution The stndrd stock solution of RIV (1000 µg ml 1 ) ws prepred in ACN:Wter (80:20 v/v) mixture. The working stndrd solutions (5.0, 10.0, 20.0, 25.0, 30.0, 35.0 nd 40 µg ml -1 ) were prepred by diluting the stock solution in the mobile phse solution. The stock solution ws kept t +4 o C where it is stble t lest one month. Stndrd solutions were dily prepred by diluting the stock solution with mobile phse solution. Preprtion of smple solution Ten tblets were weighed to get the verge weight nd grounded. An mount of powder equivlent to 10 mg of RIV ws trnsferred to 100 ml volumetric flsk nd dded 70 ml of diluent (ACN:Wter (80:20 v/v)) nd sonicted for 30 min. The volume ws mde up with solvent to obtin solution contining 100 μg ml -1 RIV. An liquot ws then removed nd centrifuged t 5000 rpm for 10 min. The solution ws filtered using 0.45 μm membrne filter pper nd diluted with mobile phse to 20 μg ml -1 before injected to the HPLC system. Preprtion of nlyticl plcebo solution Common inctive ingredients such microcrystlline cellulose (10%, 500 mg), nhydrous dibsic clciumphosphte (83%, 4150 mg), croscrmellose sodium (5%, 250 mg), colloidl silicon dioxide (%1, 50 mg), nd mgnesium sterte (%1, 50 mg) were weighed ccording to the rtios in common tblet formultion to chieve 5 g of bulk. Then, pproximtely 1 g of this bulk ws used to prepre the nlyticl plcebo solutions by pplying the sme procedure on preprtion of tblet solutions. Synthetic tblet solutions were prepred by dding known mounts of RIV stndrd solutions to the nlyticl plcebo solutions. Forced Degrdtion High Temperture 100 µl of RIV stndrd stock solution ws diluted
3 RP-HPLC method development nd vlidtion for estimtion of rivroxbn in phrmceuticl dosge forms 361 to 1000 µl by dding wter. The concentrtion of RIV ws 100 µg ml -1 in the finl solution. Then the solution ws trnsferred to centrifuge tube nd kept in wter bth for 2 h t 80 C. The solution ws cooled to room temperture (25 ± 5 C), nd then it ws diluted with mobile phse to 20 µg ml -1 nd injected into the HPLC system. Acid nd lkli hydrolysis 100 µl of RIV stndrd stock solution ws diluted to 1000 µl by dding 0.1 N hydrochloric cid, or 0.1 N sodium hydroxide. The concentrtion of RIV ws 100 µg ml -1 in the finl solution. Then the solution ws trnsferred to centrifuge tube nd kept in wter bth for 2 h t 40 o C. These solutions were cooled t room temperture (25 ± 5 C), fter they were neutrlized with suitble mount of hydrochloric cid or sodium hydroxide. The solutions were diluted with mobile phse to 20 µg ml -1 nd injected into the HPLC system. Irrdition with ultrviolet light 100 µl of RIV stndrd stock solution ws diluted to 1000 µl by dding wter. The concentrtion of RIV ws 100 µg ml -1 in the finl solution. The solution ws exposed to UV light (254 nm) combined with tungsten lmp for 24 hours t room temperture. The solution ws then diluted with mobile phse to 20 µg ml -1 nd injected into the HPLC system. Stbility studies The purpose of stbility testing is to provide evidence on how the qulity of drug product vries with time under the influence of vriety of environmentl fctors such s temperture, humidity, nd light. The stndrd stock solution of RIV (1000 µg ml -1 ) prepred in ACN:Wter (80:20 v/v) ws divided into two volumetric flsks (5 ml). These volumetric flsks were prevented from dylight nd the first one ws kept t room temperture, while the second one ws kept t 4 o C inside the refrigertor. The stbility of RIV t room temperture ws evluted in short term period (24 h), while the stbility t 4 o C ws evluted for 72 h (short-term) nd 1 month (long-term). The solutions were then diluted with mobile phse to 20 µg ml -1 nd injected into the HPLC system. RESULTS AND DISCUSSION For developing nd vlidting n HPLC method, the most common pproch is to optimize the mobile phse composition fter n pproprite column hs been selected (Synder et l., 1997). RIV is non-hygroscopic powder only slightly soluble in orgnic solvents nd it is prcticlly insoluble in wter nd queous medi. According to our observtion, RIV ws slightly dissolved in methnol (MeOH) on the preprtion of stndrd stock solutions process. Therefore, the solubility of RIV ws tested simply in vrious orgnic solvents in the initil experiments nd it ws concluded tht RIV ws clerly soluble in cetonitrile (ACN). Thus, it ws decided to use the mixture of ACN nd wter in different proportion on the seprtion of RIV through C18 column. Since cffeine could be eluted with ACN:wter mixture without using ny buffer nd it is n esy to find chemicl for qulity control lbortories, it ws used s the internl stndrd (IS) for the experiments. A well-defined pek for cffeine ws observed t 2.21 min. under the experimentl conditions. Even though the column temperture is n importnt prmeter on seprtion of orgnic compounds by HPLC, the effect of the solvent strength is usully stronger thn the effect of temperture on solute retention (Cuiru et l., 2005). It ws seen tht chnging the column temperture between o C, chnged the retention time of RIV not more thn 5% nd did not effect the retention time of IS noticebly. According to the results, it ws obvious tht RIV could be esily seprted nd nlyzed less thn 4 minutes in vrious conditions given in Tble I. However, it ws observed tht better peks shpes were obtined by incresing the temperture of the column. Since, the bckpressure of the column ws tolerble, the flow rte ws kept t 1.2 ml min -1 to improve the efficiency besides decresing the retention time. In conclusion, it ws decided to use ACN-Wter rtio s 55:45 (v/v) t 40 o C to perform the nlyses. The UV Spectrum of the RIV in mobile phse shows clerly tht 249 nm is better to use in to observe the mximum bsorbnce while it is being prevented from interference coming from mtrix components. The chromtogrms of stndrd, tblet, nlyticl plcebo solutions nd RIV solution degrded t high temperture tken under optimum conditions re given in Figure 2. System Suitbility The system suitbility test ws pplied to the chromtogrms tken under optimum conditions to check vrious prmeters such s column efficiency (pltes), pek tiling, cpcity fctor, nd resolution. Suitble resolution (>1.5) nd column efficiency (>2000) were chieved for the proposed method while the totl nlysis time ws shorter thn 4 minutes. The system suitbility results re given in Tble II. The RSD of six consecutive injections ws found to be 0.25%, nd 0.28% for IS nd RIV, respectively. All these results ssure the dequcy of
4 362 M. Çelebier, T. Reçber, E. Koçk, S. Altınöz TABLE I - Retention time of IS nd RIV on vrious conditions of mobile phse composition nd chromtogrphic column temperture Condition Mobile Phse Composition Temperture Flow Rte Retention Time ACN H 2 O o C ml min -1 IS RIV Condition 2 is selected to perform the nlysis FIGURE 2 - Representtive chromtogrms obtined under the optimum chromtogrphic conditions for RIV stndrd, RIV tblet, nlyticl plcebo solutions nd RIV solution degrded t high temperture. the proposed HPLC method for routine nlysis of RIV. Method vlidtion The proposed method ws vlidted s to selective, linerity rnge, sensitivity, precision, ccurcy, robustness nd ruggedness ccording to the ICH guideline (ICH, 2005). Forced degrdtion nd stbility studies The stbility of RIV in queous solutions ws investigted for two different purposes. The first one ws to identify the stbility of RIV nd to show the selective nlysis of RIV in vrious extreme stress conditions. The second one ws to clrify the stbility of stndrd solutions for short nd long term t room temperture nd
5 RP-HPLC method development nd vlidtion for estimtion of rivroxbn in phrmceuticl dosge forms 363 TABLE II - System suitbility prmeters for the proposed method RIV Retention Time (min) Cpcity Fctor (k ) Efficiency (N) Pek Symmetry Resolution 8.9 inside refrigertor. The ICH guideline entitled stbility testing of drug substnces nd products requires the stress testing to be crried out to elucidte the inherent stbility chrcteristics of the ctive substnce, nd provide rpid identifiction of differences tht might result from chnges in the mnufcturing processes or source smple (ICH, 2005). The im is to quntify the stndrd drug lone nd resolve its degrdtion products (Bkshi et l., 2002). As described in the experimentl section, different stress conditions were pplied: high temperture, cidbse hydrolysis nd irrdition with UV light. Under ll these conditions the degrdtion products were observed t 1.35 min (Figure 2). The method ws ble to seprte completely the degrdtion products from the intct RIV. As shown in Figure 2, it is confirmed the selectivity of the proposed method with the presence of the degrdtion products. Stbility studies of RIV t room temperture for 24 h, 4 o C refrigertion temperture for 72 h (short-term) nd 1 month (long-term) were lso investigted. Forced degrdtion nd stbility studies show tht RIV ws stble t root temperture for 24 h nd stble t 4 o C refrigertion temperture t lest for 1 month, but not stble in cidic nd lkline medis nd lso not stble in high temperture nd under the UV light. The forced degrdtion nd stbility results re given in Tble III. Selectivity Selectivity of method refers to the extent to which it cn determine prticulr nlyte(s) in complex IS mixture without interference from other components in the mixture. Selectivity of the method ws evluted by prepring the nlyticl plcebo smple, stndrd solution nd smple of commercil phrmceuticl formultion. A solution of nlyticl plcebo (contining ll the tblet excipients except RIV) ws prepred s given in the smple preprtion procedure nd injected into the HPLC system. The plcebo chromtogrms did not show ny other peks, thus, it ws confirmed the selectivity of the method. The pek purities confirmed tht the peks on the stndrd solutions, tblet solutions nd forced degrdtion solution re not interfered coming from mtrix components. The retention times of peks nd pek res were identicl for the stndrd solutions nd the tblet solutions nd the method ws cpble of seprting RIV nd IS from forced degrdtion products. The chromtogrms of stndrd, tblet, plcebo nd forcedly degrded RIV solutions were given in Figure 2. Linerity The linerity of n nlyticl procedure is its bility (within given rnge) to obtin test results, which re directly proportionl to the concentrtion (mount) of nlyte in the smple. Clibrtion curve ws constructed for RIV stndrds by plotting the concentrtions versus pek re rtios. The grph proved tht the method ws liner up to 40 µg ml -1. Eight different stndrd solutions within the liner rnge contining 5.0, 10.0, 20.0, 25.0, 30.0, 35.0 nd 40 µg ml -1 of RIV nd 40 µg ml -1 of IS were prepred nd injected into the HPLC system. The linerity ws evluted by liner regression nlysis nd the regression equtions were clculted from the clibrtion grphs, long with the stndrd devitions of the slope (Sb) nd intercept (S) of the clibrtion curve (Tble IV). Sensitivity Limit of detection (LOD) nd quntifiction (LOQ) TABLE III - Recupertion (%) of RIV fter the exposition on vrious conditions of temperture, ph nd UV light Condition Room Temperture Refrigertor Temperture Acidic Solution Bsic Solution High temperture UV light Temperture 25 o C 4 o C 40 o C 40 o C 80 o C 25 o C Time 24 h 72 h 1 month 2 h 2 h 2 h 24 h Stbility (%) b ± ± ± ± ± ± ± 0.2 RIV solutions were prepred s described in experimentl section nd prevented from dylight. b Stbility results re given s Recovery (%) ± RSD while n=6 nd the dded concentrtion of RIV is 20 µg ml -1
6 364 M. Çelebier, T. Reçber, E. Koçk, S. Altınöz TABLE IV - Linerity of RIV nlyses by the developed method Method Rnge (µg ml -1 ) Clibrtion Curve S Sb R 2 LOQ LOD HPLC y = x Bsed on six clibrtion curves where y: pek re rtio nd x: concentrtion of RIV s µg ml -1 ; S: Stndrd error of intercept nd Sb: Stndrd error of slope; R 2 : Regression coefficient; LOQ: Limit of quntittion; LOD: Limit of detection re estimted from the signl-to-noise rtio. The detection limit is defined s the lowest concentrtion level resulting in pek height of three times the bseline noise. The quntittion limit is defined s the lowest concentrtion level tht provided pek height with signl-to-noise rtio higher thn 10, with precision (RSD%) nd ccurcy (Bis%) within ±10%. LOD nd LOQ vlues of HPLC method were determined to be nd µg ml -1, respectively (Tble IV). Precision nd Accurcy Accurcy of the ssy method ws determined for both intr-dy nd inter-dy vritions using the six times nlysis of the qulity control smples. Three different concentrtions of stndrd RIV solutions (within the liner rnge) were nlyzed on six consecutive dys (inter-dy precision) nd six times within the sme dy (intr-dy precision). The obtined vlues for reltive stndrd devition (RSD) nd Bis of intr- nd inter-dy studies indicted tht the precision nd ccurcy of the method were stisfctory. The results re summrized in Tble V. Recovery In order to know whether the excipients in the phrmceuticl formultions interfere with the nlysis, the recovery tests were performed by stndrd ddition technique. Three concentrtion levels were selected nd known mounts of RIV stndrd solutions were dded into the tblet solutions. The finl concentrtions were within the liner rnge. These solutions were prepred three times nd nlyzed through the developed method. Comprison of the intercepts of clibrtion curve ( ± (men ± SE)) with stndrd dditions technique ( ± (men ± SE)) indictes tht they were identicl nd there ws no interference coming from mtrix components. The other perspective on recovery studies ws to nlyze synthetic tblet solutions by the proposed method. Synthetic tblet solutions were prepred six times nd nlyzed by the developed method nd ± 0.68 percent of the stndrd RIV were recovered from synthetic tblet solutions. Robustness The robustness of n nlyticl procedure is mesure of its cpcity to remin unffected by smll but deliberte vritions in method prmeters nd provides n indiction of its relibility during norml usge. The vritions on column temperture (± 5 o C) nd rtio of orgnic content in the mobile phse (± 5% on ACN volume) did not hve ny significnt effect on response. The pek re rtios were chnged reltively between % within these smll chnges on mobile phse component nd column temperture. The results were evluted sttisticlly, nd there were no significnt differences (p>0.05) within the results. Reproducibility Applying sme procedures by two different opertors showed the ruggedness of the developed method. The nlysis results hving no significnt difference indicte tht the proposed method is robust. TABLE V - Precision nd ccurcy of the developed method Added (mg ml -1 ) Found (mg ml -1 ) Intr-dy Precision b RSD % Accurcy c Bis % Found (mg ml -1 ) Inter-dy Precision RSD % Accurcy Bis % RIV ± ± ± ± ± ± Found: men ± stndrd error (n=6); b RSD: Reltive stndrd devition; Bis: [(Found - Added)/Added] x 100
7 RP-HPLC method development nd vlidtion for estimtion of rivroxbn in phrmceuticl dosge forms 365 Appliction of the developed method The vlidted method ws pplied for the determintion of RIV in commercilly vilble Xrelto (10 mg) tblets. Figure 2 illustrtes typicl type of HPLC chromtogrm of tblet solution of RIV t retention time 3.37 min with no interference of excipients present in tblets. The tblet nlysis results were given in Tble VI. The results of the ssy (n=6) yielded % (RSD = 1.17 nd SE = 0.53) of the lbeled clim. These results indicte tht the method is selective for the nlysis RIV without interference of the excipients. The low RSD vlue with proper ccurcy indictes the suitbility of this method for the routine nlysis of RIV. TABLE VI - Tblet nlysis results Tblet Solutions CONCLUSION Xrelto Tblets (10 mg RIV) RIV (mg) Recovery (%) Men ± SE ± ± 0.48 RSD 1.17 Bis b 0.94 RSD : Reltive stndrd devition; b Bis : [(Found - Added)/Added] x 100 In the present study, n ttempt ws mde to develop simple, ccurte, selective nd sensitive RP-HPLC method of RIV in phrmceuticl nlysis. This method is the only reported method up to dte for the determintion of RIV in phrmceuticl dosge forms. The method ws vlidted for selectivity, ccurcy, linerity, precision (inter-dy nd intr-dy), sensitivity, robustness nd ruggedness in ccordnce with ICH guidelines. The results from stress testing, including seprtion of the degrdtion product nd quntifiction of RIV fter exposure to stress conditions show the method is stbility-indicting nd cpble of determining RIV in presence of its degrdtion products, which indictes the selectivity of the method. A simple mobile phse without preprtion of ny buffer solution or dding ion-piring gents nd short run time re dvntgeous nd mke this method suitble for routine nlysis of lrge number of smples per dy. ACKNOWLEDGEMENTS The uthors re highly grteful to Byer Türk Kimy Sn. Ltd. Şti., Istnbul, Turkey, for providing the drug smples. REFERENCES BAKSHI, M.; SINGH, S. Development of vlidted stbilityindicting ssy methods-criticl review. J. Phrm. Biomed. Anl., v.28, p , CUIRU, Z.; GOODALL, D.M.; WREN, S.A.C. Elevted temperture HPLC: Principles nd pplictions to smll molecules nd biomolecules. LCGC Asi Pcific, v.8, p.48-59, DONG, M. W. Hndbook of phrmceuticl nlysis by HPLC. Elsevier: United Kingdom, v.6, p.2-3 DUGGAN, S.T.; SCOTT, L.J.; PLOSKER, G.L. Rivroxbn review of its use for the prevention of venous thromboembolism fter totl hip or knee replcement surgery. Drugs, v.69, p , INTERNATIONAL CONFERENCE ON HARMONIZATION (ICH). Text on vlidtion of nlyticl procedure: methodology: Q2(R1), Avilble t: <http://www. ich.org> Accessed on: 19 My PERZBORN, E.; KUBITZA, D.; MISSELWITZ, F. Rivroxbn: A novel, orl, direct fctor X inhibitor in clinicl development for the prevention nd tretment of thromboembolic disorders. Hämostseologie, v.27, p , ROHDE, G. Determintion of rivroxbn - novel, orl, direct Fctor X inhibitor - in humn plsm by high-performnce liquid chromtogrphy-tndem mss spectrometry. J. Chromtogr. B., v.872, p.43-50, SNYDER, L.R.; GLAJCH, J.L.; KIRKLAND, J.J. Prcticl HPLC method development. 2ed. New York: John Wiley & Sons, Chpter 1.2 TERRY, C.; SUM, L. Rivroxbn: n orl direct fctor X inhibitor for the prevention of thromboembolism. Crdiol. Rev., v.17. p , 2009.
8 366 M. Çelebier, T. Reçber, E. Koçk, S. Altınöz WORLD HEALTH ORGANIZATION. WHO technicl report series no. 957, WHO expert committee on specifictions for phrmceuticl preprtions, Forty-fourth report, Avilble t: <http://www.who.int/en/>. Accessed on: 19 My Received for publiction on 19 th June 2012 Accepted for publiction on 08 th Februry 2013