Extraction of acyclovir from pharmaceutical creams for HPLC assay. Optimization and validation of pretreatment protocols

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1 Cent. Eur. J. Chem. 6(2) DOI: /s y Centrl Europen Journl of Chemistry Extrction of cyclovir from phrmceuticl crems for HPLC ssy. Optimiztion nd vlidtion of pretretment protocols Invited pper Prskevs D. Tznvrs 1,2, Constntinos K. Zchris 1,3* 1 Lbortory of Anlyticl Chemistry, Deprtment of Chemistry, Aristotle University of Thessloniki, GR Thessloniki, Greece 2 Cosmophrm Ltd, P.O. Box 42, GR-20100, Korinthos, Greece 3 HELLAMCO S.A. Scientific Equipment, Brnch Office Vss. Olgs 65, GR-54642, Thessloniki, Greece Received 3 November 2007; Accepted 13 December 2007 Abstrct: Three simple protocols for the extrction of cyclovir from its phrmceuticl crems bsed on ultrsoniction, ultrsoniction with heting nd mgnetic stirring were evluted nd compred. Extrction kinetics were studied t different time intervls (5, 10, 15, 30 nd 60 min) nd the extrction efficiency ws determined by HPLC. The effect of concentrtion of queous NOH s the extrction medium nd the stirring speed were lso studied nd optimized. Best results were obtined with 50 ml of 0.01 mol L -1 queous NOH with mgnetic stirring speed of 500 r.p.m. HPLC nlysis involved rpid seprtion of cyclovir from the crem mtrix using mm i.d. monolithic column nd UV detection t 254 nm. Mgnetic stirring produced the best results in terms of extrction efficiency with n verge extrction yield of 100.8%, n = 16 t n optimum extrction time of 15 min. The selected protocol ws vlidted for within nd dy-to-dy precision nd ruggedness. Keywords: Acyclovir Extrction protocols Phrmceuticl crems HPLC ssy Monolithic sttionry phse Versit Wrsw nd Springer-Verlg Berlin Heidelberg. 1. Introduction Smple preprtion is criticl step in chemicl nlysis since it my introduce errors nd inccurcies in quntittive ssys. An idel smple preprtion protocol should be simple, cost effective, fst nd reproducible. Especilly in phrmceuticl qulity control, smple preprtion must ensure rpid, quntittive nd selective extrction of the ctive phrmceuticl ingredient (API) from the formultion (usully tblet, cpsule or crem) nd excipients used. Another significnt feture is the possibility of prllel multi-smple pretretment, in order to reduce totl nlysis time when lrge number of smples hve to be ssyed e.g. during new product development or vlidtion of the mnufcturing process in the phrmceuticl industry. Acyclovir (Fig. 1) is n ntivirl drug found in both tblets nd crems tht slows the growth nd spred of the herpes virus so tht the body cn fight off the infection [1]. Acyclovir does not cure herpes. It reduces pin nd helps the sores cused by the infection to hel fster. Some doctors even use cyclovir, long with other drugs, in the tretment of HIV [2]. Mild common side effects my be dirrhe, nuse, vomiting, itching nd skin rsh, while more serious side effects include hemturi, encephlopthic chnges nd elevtion of serum cretinine [3]. Messer nd Tylor hve reported the quntittive extrction of cyclovir from phrmceuticl crem mtrix of 5% w/w Zovirx using inverse nlyticl supercriticl fluid extrction [4]. Although quite effective, the proposed smple preprtion procedure is rther complicted requiring specilized instrumenttion nd strictly controlled conditions, therefore, being unttrctive for routine qulity control in n industril environment. The present study reports the results from the 140 * E-mil: czchris@gmil.com

2 P. D. Tznvrs, C. K. Zchris Figure 1. Chemicl structure of cyclovir. experimentl evlution of three protocols for the extrction of cyclovir from phrmceuticl crem mtrix of 5% w/w Hgevir crem (lot 004, Cosmophrm Ltd, Korinthos, Greece). The protocols re bsed on n lkline extrction medium of 0.01 mol L -1 NOH using one of the following: ultrsoniction, ultrsoniction with het or mgnetic stirring-bsed extrction. The protocols were evluted nd compred in terms of extrction time, efficiency nd repetbility. Additionl vlidtion experiments of the selected protocol included dy-to-dy precision nd ruggedness. Recovery of cyclovir from the crem mtrix ws determined by n HPLC method bsed on monolithiccolumn seprtion nd UV detection [5]. Monolithic columns, which hve become commercilly vilble recently [6,7], llow efficient seprtions t higher flow rtes nd lower bck-pressures thn conventionl prticulte-bsed columns. Such systems hve lredy proven to hve useful fetures for number of pplictions in the phrmceuticl industry [5,8-10]. Necessry re-vlidtion experiments were crried-out in order to ensure the efficiency of the HPLC procedure for its intended purpose. 2. Experimentl 2.1. Regents All regents were of nlyticl grde nd were provided by Merck, Germny; unless stted otherwise. HPLC mobile phse consisted of 0.2% v/v CH 3 COOH. HPLC grde wter ws used throughout this work. The mobile phse ws lwys filtered under vcuum with 0.45 μm filters (Schleicher & Schuell, Germny) nd degssed ultrsoniclly for 30 min, prior to use. Acyclovir (lot no. ACP/WS/001/03, Assy = 99.9%) reference stndrd ws provided by Mtrix Lbortories Ltd (Indi). A 1000 mg L -1 cyclovir stndrd stock solution ws prepred by dissolution of n ccurtely weighed mount (50.0 mg) in 50 ml of 0.01 mol L -1 queous NOH. The stock solution ws stble for t lest one week if kept refrigerted nd protected from light. Working solutions of cyclovir were prepred by pproprite dilutions of the stock solution in 0.01 mol L -1 queous NOH. It should be noted tht the reported cyclovir concentrtions re clculted on n nhydrous bsis. Since cyclovir my contin up to 6% of wter, it is necessry to determine its exct wter content by Krl- Fischer titrtion nd mke the pproprite corrections. A 1.0 mol L -1 queous NOH stock solution ws prepred by dissolving 40.0 g of NOH pellets in 1.0 L of de-ionized wter mol L -1 queous NOH working solution ws prepred by 100-fold dilution of the stock solution in HPLC-grde wter. All the phrmceuticl excipients for the synthesis of plcebo crem (ll excipients excluding the API, viz, propylene glycol, sodium luryl sulfte, prffin soft white, prffin liquid, cetosteryl lcohol nd poloxmer 407) used in the ccurcy studies were purchsed from domestic suppliers Apprtus An HP 1100 HPLC instrument (Hellmco S.A., Greece) ws used throughout this study. It comprised of quternry pump, vcuum degsser, column thermostt, n utosmpler nd DAD spectrophotometric detector. Chromtogrms nd chromtogrphic prmeters (pek res, retention times, S/N rtio etc) were recorded nd clculted respectively vi the Chem Sttion softwre. A RP-18e, monolithic mm i.d. Chromolith Performnce column (Merck, Germny) ws used for seprtion of cyclovir. A vcuum filtrtion system (Schleicher nd Schuell, Germny) nd 0.45 μm membrne filters (RC 55, Schleicher & Schuell, Germny) were used for the filtrtion of the mobile phse. A Mettler-Toledo DL-18 Krl Fischer titrtor (Hellmco S.A., Greece) ws used for the determintion of the wter content of cyclovir in both the working stndrd nd the rw mteril. A model 19H ultrsonic bth (Ney-ultrsonics, US) nd model HI190M mgnetic stirrer (Hnn Instruments Hells, Greece) equipped with Teflon coted mgnets (20 3 mm) were used throughout this study. In order to obtin stedy conditions, the ultrsonic bth ws operted for one hour prior to use. 141

3 Extrction of cyclovir from phrmceuticl crems for HPLC ssy. Optimiztion nd vlidtion of pretretment protocols 2.3. HPLC procedure The stndrds nd/or smples from the extrction procedures -20 μl in ll cses- were injected into the monolithic column vi the utosmpler of the HPLC instrument. The flow rte ws set t 2.0 ml min -1 in the rnge min nd t 5.0 ml min -1 in the rnge min. The column temperture ws 25 C, nd pek re ws used for signl evlution. All stndrds nd smples were injected in triplictes [5] Extrction protocols Accurtely weighed mounts of cyclovir-contining crem (100 ± 10 mg ech) were dispersed in 50 ml of 0.01 mol L -1 queous NOH. The theoreticlly expected cyclovir mss concentrtion is c. 100 mg L -1. Smples were processed vi either ultrsoniction ssocited with nd without heting t 50 C or mgnetic stirring t 500 r.p.m. for 5, 10, 15, 30 nd 60 min intervls. Five different smples were used representing ech extrction time. 5 ml portions of the resulting suspensions were filtered through disposble syringe filters with 0.45 μm pore size (Whtmn ) nd injected in triplictes in the HPLC system (5 smples 3 injections t ech time intervl for ll protocols). 3. Results nd Discussion 3.1. Anlyticl chrcteristics of the HPLC method Opertion of the HPLC system under the conditions described in [5] enbles fst elution of cyclovir t c min nd effective seprtion from its mjor impurity gunine. The peks were shrp nd the bseline stble in ll cses. However, some re-vlidtion experiments were performed in order to ensure consistency nd effectiveness of the HPLC procedure for quntifiction of cyclovir t lower concentrtion levels. The linerity of n HPLC ssy intended for phrmceuticl qulity control is usully vlidted in the rnge of % of the expected concentrtion of the API [5,11]. Since the purpose of the present work ws to study the extrction of cyclovir from the smple mtrix, it ws necessry to re-vlidte the linerity of the ssy in the significntly more extended rnge of 0 120% (n = 8; γ (cyclovir) = 5, 10, 20, 50, 70, 90, 100 nd 120 mg L -1 ). The experiments confirmed the linerity of the method in the rnge studied, with regression coefficient of Vlidtion of the regression line ws performed by the response fctor (R.F.) test [12]. The devition of the R.F. from the clibrtion curve must be within ± 3% of the experimentl slope nd is given by the eqution: The experimentl results conform to the bove mentioned limit (± 3%). The devitions of ll points on the clibrtion curve of cyclovir were in the rnge of to + 2.8% of the slope in the corresponding regression eqution. The detection (LOD) nd quntittion limits (LOQ) were estimted using the S/N criteri nd were dequte for studying the extrction of cyclovir from the crem mtrix, nmely 0.05 mg L -1 (S/N = 3) nd 0.15 mg L -1 (S/N = 10) respectively [5]. The precision of the ssy ws re-vlidted t three lower concentrtion levels compred to [5], nmely t 5, 10 nd 50 mg L -1 of cyclovir. The reltive stndrd devitions (n = 12) were excellent in ll cses, being 1.4, 1.1 nd 0.7% respectively. The ccurcy of the HPLC method ws re-vlidted in the rnge of mg L -1 cyclovir. 100 mg of plcebo crem (40.0% propylene glycol, 0.75% 12.5% sodium luryl sulfte, 12.5% prffin soft white, 5.0% prffin liquid, 6.75% cetosteryl lcohol nd 1.0% poloxmer 407) were dispersed in 50 ml of 0.01 mol L -1 NOH nd spiked with cyclovir stndrd solution to finl concentrtions of 5, 10, 50, 100 nd 120 mg L -1. The results for three smples constructed t ech concentrtion level re shown in Tble 1. Tble 1. Vlidtion of the ccurcy of the HPLC ssy. Synthetic smple Acyclovir dded (mg L -1 ) pek re intercept R.F. = γ[cyclovir] Plcebo dded (mg / 50 ml) 3.2. Evlution of the extrction procedures Hgevir crem (5.0% w/w cyclovir, Lot 004, Cosmophrm Ltd, Korinthos, Greece) ws used for the evlution of the extrction protocols, ccording to the experimentl procedures described previously. The results for the ultrsonic (with nd without heting) nd mgnetic stirring extrction processes re tbulted in Tble 2, while grphicl comprison is shown in Fig. 2. Representtive chromtogrms of n cyclovir stndrd nd phrmceuticl crem smple re depicted in Fig. 3. The experimentl results clerly showed tht cyclovir cn be extrcted quntittively nd reproducibly (1) Recovery (± SD) b (%) (± 1.3) (± 1.1) (± 0.7) (± 1.1) (± 0.8) Men of three smples. b 3 smples 3 injections ech. 142

4 P. D. Tznvrs, C. K. Zchris Tble 2. Efficiency of the extrction protocols. Extrction time(min) Extrction efficiency (± SD) (%) Ultrsonic 5 smples 3 injections ech. Ultrsonic with heting Mgnetic stirring (± 11.7) 60.2 (± 10.3) 92.6 (± 3.5) (± 8.3) 71.9 (± 7.4) (± 0.7) (± 8.6) 80.1 (± 10.2) 99.8 (± 0.6) (± 6.3) 85.6 (± 7.9) 99.6 (± 0.8) (± 2.1) 99.1 (± 1.9) (± 0.2) Figure 3. Representtive chromtogrms of cyclovir stndrd nd phrmceuticl crem t the 100% concentrtion level. Chromtogrphic conditions: V inj = 20 μl, Q = 2.0 ml min -1 in the rnge min nd t 5.0 ml min -1 in the rnge min, Mobile Phse = 0.2% v/v CH 3 COOH, T = 25 o C, λ = 254 nm. Figure 2. Grphicl comprison of the extrction procedures. within 10 min by simple mgnetic stirring. On the other hnd, ultrsoniction required 60 min for quntittive extrction nd the reproducibility ws poor. The combintion of ultrsoniction with simultneous heting t 50 C did not result in significnt improvement in the extrction yield. Fifteen minutes of extrction with mgnetic stirring ws selected s optiml for further experiments Optimiztion of mgnetic stirring bsed extrction Effect of the mount of NOH concentrtion The effect of the concentrtion of queous NOH used s extrction medium ws studied in the rnge of mol L -1. The experimentl results re depicted in Fig. 4. Quntittive extrction of cyclovir ws chieved for NOH concentrtions higher thn mol L mol L -1 NOH ws selected s the optiml concentrtion for further studies Effect of stirring speed The effect of stirring speed on the extrction efficiency ws studied in the rnge of r.p.m.. The experimentl results re depicted in Fig. 5. Stirring speeds higher thn 200 r.p.m. ensured quntittive extrction of the nlyte. The vlue of 500 r.p.m. ws selected for further experiments. Figure 4. Effect of the mount concentrtion of NOH on the extrction of cyclovir Vlidtion of extrction bsed on mgnetic stirring The optimum extrction procedure selected viz. 15 min of mgnetic stirring t 500 r.p.m. using 0.01 mol L -1 queous NOH s extrction medium ws vlidted for within nd for dy-to-dy precision nd ruggedness Within nd dy-to-dy precision Eight extrction experiments were crried out t one hour intervls during working dy (within-dy precision), while two experiments per dy were crried out for period of four consecutive working dys (dy-to-dy precision). All smples from the dy-to-dy experiments were filtered nd refrigerted in drk on completion of the experiment nd nd nlyzed together s smple set in order to void dditionl dy-to-dy vritions from the HPLC ssy. The experimentl results were stisfctory in ll cses nd hd within- nd dy-to- 143

5 Extrction of cyclovir from phrmceuticl crems for HPLC ssy. Optimiztion nd vlidtion of pretretment protocols dy RSDs of 3.1% nd 4.7% respectively. The men extrction yield of ll experiments ws 100.8% Ruggedness of the extrction procedure The ruggedness of the extrction protocol ws vlidted by smll deliberte vritions of criticl prmeters ffecting the procedure round the optiml vlues. The extrction time ws vried in the rnge of min, the concentrtion of the extrctnt in the rnge of mol L -1 nd the stirring speed in the rnge of r.p.m.. The experimentl results re shown in Tble 3. No significnt effect on the extrction yield ws observed verifying the ruggedness of the selected extrction protocol. 4. Conclusions Mgnetic stirring proved superior to the ultrsonicbsed procedures for the extrction of cyclovir from phrmceuticl crems both, in terms of rpidity nd precision. Optimiztion nd vlidtion experiments confirmed tht cyclovir could be extrcted quntittively from the crem mtrix within 15 min in 0.01 mol L -1 NOH t 500 r.p.m., while the within nd dy-to-dy precision nd ruggedness of the protocol were excellent in ll cses. Compred with the procedure proposed by Messer nd Tylor bsed on supercriticl fluid extrction [4], the proposed methodology is eqully effective, much simpler nd ttrctive to routine qulity control of phrmceuticl formultions. The evluted extrction protocol is currently being successfully pplied to the qulity nd stbility control of cyclovir in 5% w/w Hgevir crem t the fcilities of Cosmophrm Ltd. Figure 5. Effect of stirring speed on the extrction of cyclovir. Tble 3. Ruggedness of the extrction protocol. Extrction prmeters Extrction yield (± SD) / % Optiml conditions ± 0.8 Effect of extrction time 12 min ± min 99.1 ± 0.9 Effect of the mount concentrtion of NOH mol L ± mol L ± 0.4 Effect of stirring speed 400 r.p.m ± r.p.m ± 0.9 For experimentl detils see text. Acknowledgments The uthors would like to thnk Ms Aspsi Verdouks nd Mrs Theodor Bllom (Production Deprtment, Cosmophrm Ltd) for technicl support nd useful discussion. References [1] Yhoo Helth URL: [2] Helthsqure URL: com [3] HIVdent URL: [4] D.C. Messer, L.T. Tylor, Anl. Chem. 66, 1591 (1994) [5] P.D. Tznvrs, D.G. Themelis, J. Phrm. Biomed. Anl. 43, 1526 (2007) [6] K. Cbrer, D. Lubd, H-M. Eggenweiler, H. Minkuchi, K. Nknishi, J. High Resol. Chromtogr. 23, 93 (2000) [7] K. Nknishi, N. Sog, U.S. Ptent No 5, 624, 875, 1997 [8] P.D. Tznvrs, D.G. Themelis, Anl. Chim. Act 581, 89 (2007) [9] P.D. Tznvrs, D.G. Themelis, J. Phrm. Biomed. Anl. 43, 1483 (2007) [10] S. El Deeb, L. Preu, H Wtzig, J. Phrm. Biomed. Anl. 44, 85 (2007) [11] Interntionl Conference on Hrmoniztion of Technicl Requirements for Registrtion of Phrmceuticls for Humn Use, Vlidtion of Anlyticl Procedures: Methodology (Q2B). [12] J. M. Green, Anl. Chem. 68, 305A (1996) 144