- Email: [email protected]
Effect of Cimetidine on the Pharmacokinetics of Fentiazac in Rats
Effect of Cimetidine on the Pharmacokinetics of Fentiazac in Rats DON-SUNKWEON,CHANG-KOO SHIM',
AND
.
MIN-HWALEE
Received April 27,1992,from the Department of Pharmaceutics, College of Pharmacy, Seoul National University, Shinlim-Dong, Kwanak-Gu, Accepted for publication January 13,1993. Seoul 757-742, Korea. hydroxyphenyl-4-p-chlorophenyl-thiazol-5-ylacetic acid (phydroxy FT; 2) probably as conjugates that in part undergo subsequential hydrolysis in the gastrointestinal tract.9 Analyses of the feces and urine samples collected up to 5 days after iv infusion of saline (control)or CM. The infusion of CM was conducted the dosing showed that 37%of the dose is excreted as a n intact to achieve steady-state plasma concentrations (Cs,)of CM of 30 and 60 pg/mL. In the control rats, the plasma disposition of FT and its major form, 50% as p-hydroxy FT, 8%as glucuronidelsulfate conjumetabolite, phydroxy FT, followed a classical drug-metabolite profile gates of the p-hydroxy FT, and 8% as unidentified minor irrespective of FT dose. The plasma level of phydroxy FT was compametabolites.9 The plasma concentrations of p-hydroxy FT rable with that of FT. The disappearance of FT from the rat plasma was after a single oral dose of FT (200 mg) to humans were of a significantly delayed by the CM infusion, and phydroxy FT was undecomparable order of magnitude to those of FT.lO The presence tectable in the plasma in CM-treated rats. The total body clearance (CLJ of the substantial concentrations of p-hydroxy FT in plasma of FT was decreased to 2&50% of the control value in CM-treated rats, appears to be pharmacologically insignificant in terms of implying that FT metabolism to phydroxy FT is almost completely anti-inflammatory and analgesic activities.8 impaired by CM. The CL, values in rats with different C, of CM (30and 60 pg/mL) were not significantlydifferent from each other. The distribuFT is usually administered chronically, and one of the tion volume of FT at steady state (Vd,,) was decreased to 60-70% of the possible side effects of FT is peptic mucosal bleeding.11 control value by the CM infusion at higher doses of FT (10and 20 mg/kg). Frequently, cimetidine (CM, N-cyano-N'-methyl-N"-[2-[[(5The decreases in Vd,, and CL, seem not to be related to the binding of methyl-1H-imidazol-4-yl)methyl]thio]ethyllguanidine) may FT to plasma protein because the binding of FT was not influenced by be prescribed for the control of this peptic mucosal bleeding.12 CM. In clinical settings,the magnitude of the pharmacokinetic difference CM is widely used as an H,-antagonist for the treatment of may warrant dose adjustment to avoid toxic effects of FT when peptic ulcers and other hypersecretory conditions.l"l6 Nevadministered with CM. ertheless, the pharmacokinetic interactions of FT with CM have not been studied. Drug interactions caused by CM have been well characterFentiazac (FT, 2-phenyl-4-p-chlorophenyl-thiazol-5- ized, especially with regard to the hepatic clearance of antipyrine,17 theophylline,17diazepam,ls chlordiazepoxide,l9 ylacetic acid, 11,is a nonsteroidal anti-inflammatory agent172 propranolol,20 warfarin,21 phenytoin,22 quinidine,zs and that is indicated especially in cases where analgesic and lidocaine.23 CM has been reported to inhibit phase I-depenantipyretic actions are required in addition to the antident biotransformation of drugs,24-26 possibly by binding to inflammatory effect. A large number of clinical studies have the heme moiety in cytochrome P-450.27CM may also reduce been carried out with FT, and its efficacy has been established hepatic blood flow affecting the elimination of drugs where in conditions such as rheumatoid arthritis,3 osteoarthritis,4 clearance is largely blood flow dependent.20 tendinitis and bursitis,435 as well as in sport trauma.6 FT has The objective of this study was to compare the pharmacoalso proved to be well tolerated on long-term administration.7 kinetics of FT in the presence of varying doses of CM. CM After a single oral administration of a 200-mg dose to increases oral bioavailability of some acid-unstable drugs humans, FT was absorbed rapidly, with a time to reach through elevating the pH of the gastric juice.2s.29 To eliminate maximal concentration (tmax)ranging from 0.75 to 3 h, and the experimental artifact of intestinal pH change caused by was eliminated rapidly in a curvilinear fashion, so that CM, the intravenous (iv) rather than oral route was chosen for concentrations were only 1%of their maximum value by 12 h the administration of FT and CM in this study. after dosing.8 Most of the oral dose (200 mg) was excreted via the feces (67%)and urine (18%),where the fecal elimination Experimental Section was attributed to the biliary excretion of FT and 2-pAbstract 0 The effect of cimetidine (CM) on the pharmacokinetics of fentiazac (FT) was studied in six rats. FT was administered by intravenous (iv) bolus injection at doses of 5, 10,and 20 mg/kg to rats receiving
OH (1) Fentiazac
952 / Journal of Pharmaceutical Sciences Vol. 82, No. 9, September 1993
(2) pHydroxyfentiazac
Materials-FT (11,p-hydroxy FT (2), and [2,4-di-(p-methoxyphenyl)thiazol-5-yllacetic acid were kindly provided from Wyeth Laboratory (Princeton, NJ).CM was supplied by 11-Dong Pharmaceutical Company (Seoul, Korea). SK&F 92373 was provided from SK&F (Herts, England). HPLC grade methanol and acetonitrile were purchased from Merck (Frankfurt,Germany). 1-Octanesulfonic acid (Waters, Milford, MA), heparin (Choong-Wae Pharmaceutical Company, Seoul, Korea) were used as purchased.All glassware used in the study was silanized to prevent FT adsorption.10 Drug Administration and Sampling-Male Wistar rats, weighing 250-270 g, were used. Rats were fasted overnight (16-18 h) prior to surgery. The femoral vein and artery of lightly anesthetized (ether) rats were cannulated with PE-50 polyethylene tubing. Then, the rats were kept in a supine position during the experiment by fixing their legs to the operation board with cotton threads and allowed to recover completely from the anesthesia (- 1 h) before administration of drugs. 0022-3549/93/0900-0952$02.50/0 0 1993, American Pharmaceutical Association
A preliminary iv bolus study (CM at 60 mgkg) was performed to calculate the loading dose and infusion rate of CM to achieve steady-state concentrations (C,,) of 30 and 60 pg/mL. Based on the calculation, 30-and 60-mgkg doses of CM were injected by iv bolus, followed by constant iv infusion through the femoral vein cannula at respective rates of 155 and 310 mg/kg/h. The resultant C, values of CM were attained within 30 min, with a concentration deviation of -5 &mL. CM concentration in plasma was assessed by HPLC30 with SK&F 92373 as an internal standard. Thirty minutes after the start of the CM infusion, the infusion was temporarily stopped and FT was injected through the femoral vein cannula. Three doses (5,10, and 20 mg/kg) of FT were given by iv bolus injection to the rats with two different plasma levels of CM (30 and 60 pg/mL). After administration of FT, the cannula was reconnected, and the CM infusion was resumed. The infusion-stop for FT administration usually took <30 s so its effect on the plasma C, of CM was considered negligible. The infusion was continued to the end of each experiment. Blood samples (120 pL) were then taken at 2.5,7.5, 10, 15, 20, 30, 45, 60, 90, and 120 min and placed in heparinized polyethylene centrifuge tubes. Plasma (50 pL) was separated by centrifugation in a table-top Microfuge (Beckman Instruments, Fullerton, CAI. The plasma was stored at -20 "C until FT analysis by HPLC. Each experimental group consisted of six rats. HPLC Assay of Fentiazac and p-Hydroxy FT in Plasma and Buffel--FT and p-hydroxy FT concentrations in plasma or in buffer were determined by the HPLC method of Dowell,lO with 2,4-di-[(pmethoxyphenyl)thiazo1-5-yllacetic acid as internal standard. The standard curves were linear in the concentration ranges of 5 to 200 pg/mL for FT and 2.5 to 60 pg/mL for thep-hydroxy metabolite. The detection limit for this assay was 1 pg/mL for both FT and its metabolite. The absolute recovery for both compoundswas >95% and was reproducible. The within- and between-day variability of the assay was <3% throughout the examined concentration range. Plasma Protein Binding Study-The study was conducted to test whether CM (at the concentrations of either 30 or 60 pg/mL) affects the binding of FT to plasma protein. Blank blood was obtained by carotid artery puncture, and the plasma was prepared by centrifugation (6000 x g for 10 min) at room temperature. Equilibrium dialysis was performed at room temperature for 15 h31 with a semipermeable membrane (type 18/32;Visking Company, Chicagu, IL) against isotonic Tris-HC1buffer (pH 7.4).FT and CM were added to the plasma chamber side to achieve final concentrations of 50 pg/mL for FT and 30 or 60 pg/mL for CM. Twenty microliters of the buffer was taken at 15 h and analyzed for FT by HPLC. Pharmacokinetic and Statistical Analysis-The pharmacokinetics of both FT and CM could be described by a two-compartment open model. The plasma data was fitted to the equation of the model with the aid of nonlinear regression program MULTI.32 Pharmacokinetic parameters [total plasma clearance (CL,), distribution volume at steady state (Vd,,), and mean residence time (MRT)] of FT following iv injection to the rats receiving CM infusion were calculated as follows:
CLt = Dose/AUC
(1)
VD,,= Dose * AUMC/AUC2
(2)
MRT = AUMC/AUC
(3)
Results and Discussion Plasma disappearance curves of FT (5,lo-, and 2O-mg/kg dose) with or without CM infusion are shown in Figures 1-3. In the control rats (without CM infusion), the plasma disposition of FT and its major metabolite, p-hydroxy FT, followed a classical drug-metabolite profile irrespective of FT dose. The plasma pharmacokinetics of FT could be best described by the conventional two-compartment open model. The plasma disappearance of FT was significantly retarded by the CM infusion and, as a result, the plasma concentrations of FT were greatly elevated. Most surprisingly, the p-hydroxy FT level in the plasma of CM-infused rats was so low (below the detection limit of 1 pg/mL) that it was not detectable during the experimental period irrespective of the FT doses of 5,10, and 20 mgkg. However, the two C,, values of plasma CM did not differ significantly in the effect on the disposition of FT. Table I summarizes the effect of the CM infusion at two different rates on the pharmacokinetic parameters of FT. The C,, of CM following CM infusion was successfully kept constant at either -30 or 60 pg/mL during the experimental period. The C,, was not affected by the dose of FT injected; thus, the results were expressed (Table I) as mean f SD of all the studies for three FT doses. In the control rats, FT showed linear pharmacokinetics: there was no dose dependency in the tIl2, CL,,Vd,,,and MRT in the range of FT doses examined. However, the pharmacokinetic parameters (except CLJ were changed by the CM infusion in an FT dose-dependent manner. At a low dose (5 mg/kg) of FT, the tl12and MRT of FT were increased significantly without significant Vd,,change. The MRT was increased fourfold and, as a consequence, the CL, of FT was decreased to one-fourth by the CM infusion. Although the CM infusion affected these pharmacokinetic parameters of FT, the effect of different C,, of CM on these Parameters was not statistically different. This result indicates that the plasma C,, level of -30 pg/mL is sufficient to
In eqs 1 3 , AUC and AUMC denote area under the plasma FT concentration-time curve from time zero to infinity and area under the first moment of the plasma FT concentration-time curve from time zero to infinity, respectively. The AUC and AUMC were calculated by the trapezoidal method from 0 to 120 min and an extrapolation from 120 min to infinity with the elimination rate constant (B). The plasma half-life (tl,.Jof FT was calculated by eq 4:
To compare the means of pharmacokinetic parameters from control and CM-treated groups, a two-way ANOVA was used. A p value of ~0.05was considered to be statistically significant throughout the analysis. All results are expressed as mean f SD:
Flgure 1-Mean ( 2 SD;n = 6) plasma concentration-time profiles of FT and phydroxy FT following bolus iv administration of FT at a dose of 5 mg/kg with or without co-infusion of CM. Key: (0)FT in saline-infused (control) group; (0)phydroxy FT in saline-infused (control) group; (A) FT in CM-infused group (C, = 30 pg/mL); (A) FT in CM-infused group (C,, = 60 pg/rnL). Journal of Pharmaceutical Sciences/ 953 Vol. 82, No. 9, September 1993
Table I-Effect of CM Infusion on the Pharmacoklnetlc Parameters of FT In Rats.
Fr
Dose, mglkg 5
10
20
Parameter f,,2, min
Without cM
With CM at
, C (pg/mL) of:
(Control)b
32.5 f 4.2
58.5 f 4.8
48.1 f 2.1
CL,, mUmin/kg 7.2 f 0.3 Vd,,, mUkg 281.5 f 11.2 MRT, min 38.6 f 2.7 47.2 f 1.3 f,,2, min 6.9 f 0.2 CL,, mL/min/kg 280.6 2 18.3 Vd,, mUkg MRT, min 40.0 f 1.8 f,,*, min 46.5 f 1.8 7.6 f 0.2 CL,, mL/min/kg Vd,,, mUkg 272.9 f 11.7 MRT, min 37.1 f 1.2
86.7 f 4.5' 90.8 f 5.1' 1.7 f 0.4' 1.7 f 0.4' 260.7 f 18.4 250.9 f 30.1 150.6 f 10.3' 150.3 f 14.3' 85.3 f 4.2' 49.5 f 3.1 3.2 f 0.3' . 2.2 f 0.3' 182.6 f 12.3' 220.4 2 19.2' 102.9 f 7.2" 57.5 f 5.0' 52.0 f 2.3 53.2 2 2.8 2.3 f 0.4' 2.4 f 0.3' 163.0 f 19.1' 168.3 f 36.4' 68.2 f 5.8' 74.2 2 8.1'
a Expressed as mean f SD of six experiments. Saline without CM was infused. Significantly different from the respective control group (p c 0.005). Significantly different from the respective control group (p c 0.01).
'
60
120
=(&.I Flgure 2-Mean (fSD; n = 6) plasma concentration-time profiles of FT and phydroxy FT following bolus iv administration of FT at a dose of 10 mg/kg with or without co-infusion of CM. For symbols, see Figure 1.
I
60
I
120
=(*.I Flgure &Mean (fSD; n = 6) plasma concentration-time profilesof FT and phydroxy FT following bolus iv administration of FT at a dose of 20 mg/kg with or without co-infusion of CM. For symbols, see Figure 1.
induce the drug interaction with FT. At higher doses of FT (10 and 20 m a ) , the t1,2,CL,, and MRT values of FT were also changed in a similar manner by the CM infusion. However, as 954 I Journal of Pharmaceutical Sciences Vol. 82, No. 9, September 1993
the dose of FT becomes higher, the increase in t1,2and MRT and the decrease in the CL, induced by the CM infusion became less significant. But, on the contrary to the case of lower FT dose (5 mg/kg), the Vd,, of FT was decreased significantly by the CM infusion at higher FT doses. Here again, the two levels of plasma CM did not d e c t these parameters of FT differently. The FT dose-dependent,but CM level-independent change in these pharmacokinetic parameters of FT are of great interest. The binding of FT to plasma protein was unaffected by the presence of CM: the percent of bound FT in the plasma of the control rats was 85.0 ? 2.4 (mean ? SD, n = 61, which is consistent with the previous report,31 and was 90.0 2 4.4 and 84.7 ? 2.3 at C,, of values 30 and 60 pg/mL, respectively. Therefore, the decrease in Vd,,of FT in the presence of CM could not be explained in terms of binding to plasma protein. Decreased binding of FT to body tissues might be an explanation. However, there is no evidence available at present to support tissue binding or its change by the CM infusion. More studies should be performed to elucidate the exact source of the Vd,,change. Regardless of the source of the Vd,,change, our data clearly indicate that CM interferes with the elimination of FT: The CL, of FT was decreased to one-half or one-fourth of the control value by the CM infusion. The two C,, levels of CM (30 and 60 pdmW exerted a similar effect on the CL, of FT. Besides, the CL, change was independent of the FT dose, which is contrary to the case of the other pharmacokinetic parameters. The decrease in the CL, of FT by the CM infusion was also supported by the absence of the major metabolite, p-hydroxy FT, in the plasma of the rats (Figures 1-3). No remarkable peaks except FT appeared in the HPLC chromatograms of the plasma samples from the CM-infused rats, implying the absence of any compensatory metabolic pathway of FT other than hydroxylation. The available evidence indicates that CM binds to cytochrome P-450 via its imidazole ring structure, thereby reducing the interaction between P-450 and other substrates.33 Because of the binding of CM to P-450, phase I metabolic reactions, such as hydroxylation, will be impaired, but the P-450-independent reactions, such as glucuronidation, may be spared.26-27,33 Because the hydroxylation occupies almost 90% of the metabolic pathway of FT,9 blockade of the hydroxylation may mean the blockade of metabolism itself. The absence of detectable p-hydroxy FT in the plasma of the CM-infused rats seems to reflect that FT metabolism (hydroxylation) wag completely inhibited
by the CM infusion. The decrease in the CL, of FT by CM could be attributed to the inhibition of the metabolism by CM.24-27 More direct and comprehensive studies including an in vitro metabolism study with hepatic microsomes are needed before any conclusion on the mechanism of the CM-FT interaction is made. Feely et d.20 have reported that the acute CM administration T caused 25% decrease in liver blood flow. However, assuming I is mainly eliminated by hepatic metabolism,94 FT is not a high clearance drug. Therefore, changes in hepatic blood flow would not d e c t the CL, of E"r significantly. Moreover, a 25% decrease of hepatic blood flow may not be sufficient to explain the threeto fourfold difference in the CL,. In conclusion, our data show that co-administration of CM changes the pharmacokinetics of FT dramatically: CM delayed the elimination of FT significantly, probably through inhibition of hydroxylation of FT. This hypothesis is supported by the absence ofp-hydroxy FT, a major metabolite of FT, in the plasma. In clinical settings, if CM is coadministered, the magnitude of difference in the pharmacokinetics of FT caused by CM may warrant dose adjustment of FT to avoid toxic effects of FT.
References and Notes 1. Brown, K.;Cavalla, J. F.; Green, D.; Wilson, H. B. Nature 1968, 219,164-167. 2. Brown, K.;Cater, D. P.; Cavalla, J. F.; Green, R. A. J. Med. Chem. 1974,17,1177-1181. 3. Katona, G.; Bondani, A. Cum. Med. Res. Opin. 1979,6,Suppl. 2, 71-78. 4. Famaey, J. P.; Ginsberg, F. Cum. Med. Res. Opin. 1983, 8, 675-681. 5. Wielandts, L.;Dequeker, J. Curr. Med. Res. Opin. 1979,6,Suppl. 2,85-89. 6. Rugginenti, A.Med. Sport 1980,33,117-124. 7. Antognetti, R.Minerva Ortoped. 1978,29,241-248. 8. Dowell, P. S. Xenobwtica 1984,14,947-953. 9. Franklin, R.A.; Norris, R.; Shepherd, N. W.;Rhenius, S. T. Xenobiotica 1984,12,955-960. 10. Dowell, P. S. Analyst 1983,108, 1535-1537.
11. Welch, R.W.; Bentek, H. L.; Harris,S. C. Gastroenterology1978, 74,459463. 12. MacKercher, P. A.; Ivy, K.J.; Baskin, W. N.; Krause, W. J. Ann. Intern. Med. 1977,87,676. 13. Freston. J. W. GaPtroenteroloev 1978.74.426-430. 14. Binder,'H. J.; Cocoa, A.; Crozley, R:J. ktroenterology 1978, 74. 380388. 15. La B m y , J. S.; Misciwicz, J.; Edward, J. Gut 1979,20,892-895. 16. Wesdrop, E.;Bartelman, J.; Pape, K. Gastroenterology 1978,74, 821-824. 17. Roberts, R. K.;Grice, J.; Wood, L.; Petroff, V.; McGuffie, C. Gastroenterology 1981,81,19-21. 18. Klotz, U.;Reimann, I. N. Engl. J. Med. 1980,302,1012-1014. 19. Patwardhan, R.; Johnson, R.; Shechan, J.;Desmond, P.; Wilkinson, G.; Hoyumpa, A; Branch, R.; Shenker, S. Gastroenterology 1981,80.1344. 20. Feely, J.; Wilkinson, G. R.; Wood, A. J. N. Engl. J. Med. 1981, 304,692-695. 21. Serhn, M. J.; Sibeon, R. G.; Mossman, S.; Breckrenrid A. M.; Williams, J. R. B.; Atwood, J. L.; Willoughby, J. M. !?Lancet 1979,2,317-319. 22. Neuvonen, P. J.; Tokola, R. A.; b t e , M. Eur. J. Clin. Phurmacol. 1981,21,215-220. 23. Fruncillo, R.J.; DiGregorio, G. J.; Soll, A. J. Phurm. Sci. 1983, 72,826-828. 24. Puurenen, J.; Sotaniemi, E.; Pelkonen, 0. Eur. J. Clin. Pharmacol. 1980,18,185-187. K. P.; Patwardhen, R. V.; Avant, G. R.; Mitchell, M. C.; 25. r, S. Gastroenterology 1981,80,1344. 26. Knodell, R. G.;Holtzmann, J. L.; Crankshaw, D. L.; Steele, N. M.; Stanley, L.N. Gastroenterology 1982,82,84-88. 27. Wilkinson, C. F.; Hetnarski, K.;Hicks, L. J. Pest. Biochem. Physwl. 1974,4,299-312. 28. Khoury, W.; Geraci, K.; Askari, A.; Johnson, M. Gastroenterology 1979,76,1169. 29. Fairfax, A. J.; Adam, J.; Pagan, K. S. Br. Med. J. 1978,1, 820. 30. Boutagy, J.;More, D. G.; Munro, I. A.; Schenfield, G. M. J. Lip. Chromatogr. 1984,7, 1651-1664. 31. Fumero, S.;Mondini, A.; Silvestri, S.; Zanolo, G. Pharm. Res. Comm. 1980.12.4148. 32. Yamaoka, K:; TAgawara, Y.; Nakagawa, T.;Uno, T.J. Phurm. l b n . 1981,4,87-85. 33. Somogyi, A.;.Gugler, R. Clin. Pharmacokinet. 1982,7,23-41. 34. Zanolo, G.;Giachetti, S.; Mondino, A.; Silvestri, S. Arzneim.Forsch.lDrug Res. 1980,31,109S1104.
ZK&
Journal of Pharmaceutical SciencesI 955 Vol. 62, No. 9, September 1993
AND
.
MIN-HWALEE
Received April 27,1992,from the Department of Pharmaceutics, College of Pharmacy, Seoul National University, Shinlim-Dong, Kwanak-Gu, Accepted for publication January 13,1993. Seoul 757-742, Korea. hydroxyphenyl-4-p-chlorophenyl-thiazol-5-ylacetic acid (phydroxy FT; 2) probably as conjugates that in part undergo subsequential hydrolysis in the gastrointestinal tract.9 Analyses of the feces and urine samples collected up to 5 days after iv infusion of saline (control)or CM. The infusion of CM was conducted the dosing showed that 37%of the dose is excreted as a n intact to achieve steady-state plasma concentrations (Cs,)of CM of 30 and 60 pg/mL. In the control rats, the plasma disposition of FT and its major form, 50% as p-hydroxy FT, 8%as glucuronidelsulfate conjumetabolite, phydroxy FT, followed a classical drug-metabolite profile gates of the p-hydroxy FT, and 8% as unidentified minor irrespective of FT dose. The plasma level of phydroxy FT was compametabolites.9 The plasma concentrations of p-hydroxy FT rable with that of FT. The disappearance of FT from the rat plasma was after a single oral dose of FT (200 mg) to humans were of a significantly delayed by the CM infusion, and phydroxy FT was undecomparable order of magnitude to those of FT.lO The presence tectable in the plasma in CM-treated rats. The total body clearance (CLJ of the substantial concentrations of p-hydroxy FT in plasma of FT was decreased to 2&50% of the control value in CM-treated rats, appears to be pharmacologically insignificant in terms of implying that FT metabolism to phydroxy FT is almost completely anti-inflammatory and analgesic activities.8 impaired by CM. The CL, values in rats with different C, of CM (30and 60 pg/mL) were not significantlydifferent from each other. The distribuFT is usually administered chronically, and one of the tion volume of FT at steady state (Vd,,) was decreased to 60-70% of the possible side effects of FT is peptic mucosal bleeding.11 control value by the CM infusion at higher doses of FT (10and 20 mg/kg). Frequently, cimetidine (CM, N-cyano-N'-methyl-N"-[2-[[(5The decreases in Vd,, and CL, seem not to be related to the binding of methyl-1H-imidazol-4-yl)methyl]thio]ethyllguanidine) may FT to plasma protein because the binding of FT was not influenced by be prescribed for the control of this peptic mucosal bleeding.12 CM. In clinical settings,the magnitude of the pharmacokinetic difference CM is widely used as an H,-antagonist for the treatment of may warrant dose adjustment to avoid toxic effects of FT when peptic ulcers and other hypersecretory conditions.l"l6 Nevadministered with CM. ertheless, the pharmacokinetic interactions of FT with CM have not been studied. Drug interactions caused by CM have been well characterFentiazac (FT, 2-phenyl-4-p-chlorophenyl-thiazol-5- ized, especially with regard to the hepatic clearance of antipyrine,17 theophylline,17diazepam,ls chlordiazepoxide,l9 ylacetic acid, 11,is a nonsteroidal anti-inflammatory agent172 propranolol,20 warfarin,21 phenytoin,22 quinidine,zs and that is indicated especially in cases where analgesic and lidocaine.23 CM has been reported to inhibit phase I-depenantipyretic actions are required in addition to the antident biotransformation of drugs,24-26 possibly by binding to inflammatory effect. A large number of clinical studies have the heme moiety in cytochrome P-450.27CM may also reduce been carried out with FT, and its efficacy has been established hepatic blood flow affecting the elimination of drugs where in conditions such as rheumatoid arthritis,3 osteoarthritis,4 clearance is largely blood flow dependent.20 tendinitis and bursitis,435 as well as in sport trauma.6 FT has The objective of this study was to compare the pharmacoalso proved to be well tolerated on long-term administration.7 kinetics of FT in the presence of varying doses of CM. CM After a single oral administration of a 200-mg dose to increases oral bioavailability of some acid-unstable drugs humans, FT was absorbed rapidly, with a time to reach through elevating the pH of the gastric juice.2s.29 To eliminate maximal concentration (tmax)ranging from 0.75 to 3 h, and the experimental artifact of intestinal pH change caused by was eliminated rapidly in a curvilinear fashion, so that CM, the intravenous (iv) rather than oral route was chosen for concentrations were only 1%of their maximum value by 12 h the administration of FT and CM in this study. after dosing.8 Most of the oral dose (200 mg) was excreted via the feces (67%)and urine (18%),where the fecal elimination Experimental Section was attributed to the biliary excretion of FT and 2-pAbstract 0 The effect of cimetidine (CM) on the pharmacokinetics of fentiazac (FT) was studied in six rats. FT was administered by intravenous (iv) bolus injection at doses of 5, 10,and 20 mg/kg to rats receiving
OH (1) Fentiazac
952 / Journal of Pharmaceutical Sciences Vol. 82, No. 9, September 1993
(2) pHydroxyfentiazac
Materials-FT (11,p-hydroxy FT (2), and [2,4-di-(p-methoxyphenyl)thiazol-5-yllacetic acid were kindly provided from Wyeth Laboratory (Princeton, NJ).CM was supplied by 11-Dong Pharmaceutical Company (Seoul, Korea). SK&F 92373 was provided from SK&F (Herts, England). HPLC grade methanol and acetonitrile were purchased from Merck (Frankfurt,Germany). 1-Octanesulfonic acid (Waters, Milford, MA), heparin (Choong-Wae Pharmaceutical Company, Seoul, Korea) were used as purchased.All glassware used in the study was silanized to prevent FT adsorption.10 Drug Administration and Sampling-Male Wistar rats, weighing 250-270 g, were used. Rats were fasted overnight (16-18 h) prior to surgery. The femoral vein and artery of lightly anesthetized (ether) rats were cannulated with PE-50 polyethylene tubing. Then, the rats were kept in a supine position during the experiment by fixing their legs to the operation board with cotton threads and allowed to recover completely from the anesthesia (- 1 h) before administration of drugs. 0022-3549/93/0900-0952$02.50/0 0 1993, American Pharmaceutical Association
A preliminary iv bolus study (CM at 60 mgkg) was performed to calculate the loading dose and infusion rate of CM to achieve steady-state concentrations (C,,) of 30 and 60 pg/mL. Based on the calculation, 30-and 60-mgkg doses of CM were injected by iv bolus, followed by constant iv infusion through the femoral vein cannula at respective rates of 155 and 310 mg/kg/h. The resultant C, values of CM were attained within 30 min, with a concentration deviation of -5 &mL. CM concentration in plasma was assessed by HPLC30 with SK&F 92373 as an internal standard. Thirty minutes after the start of the CM infusion, the infusion was temporarily stopped and FT was injected through the femoral vein cannula. Three doses (5,10, and 20 mg/kg) of FT were given by iv bolus injection to the rats with two different plasma levels of CM (30 and 60 pg/mL). After administration of FT, the cannula was reconnected, and the CM infusion was resumed. The infusion-stop for FT administration usually took <30 s so its effect on the plasma C, of CM was considered negligible. The infusion was continued to the end of each experiment. Blood samples (120 pL) were then taken at 2.5,7.5, 10, 15, 20, 30, 45, 60, 90, and 120 min and placed in heparinized polyethylene centrifuge tubes. Plasma (50 pL) was separated by centrifugation in a table-top Microfuge (Beckman Instruments, Fullerton, CAI. The plasma was stored at -20 "C until FT analysis by HPLC. Each experimental group consisted of six rats. HPLC Assay of Fentiazac and p-Hydroxy FT in Plasma and Buffel--FT and p-hydroxy FT concentrations in plasma or in buffer were determined by the HPLC method of Dowell,lO with 2,4-di-[(pmethoxyphenyl)thiazo1-5-yllacetic acid as internal standard. The standard curves were linear in the concentration ranges of 5 to 200 pg/mL for FT and 2.5 to 60 pg/mL for thep-hydroxy metabolite. The detection limit for this assay was 1 pg/mL for both FT and its metabolite. The absolute recovery for both compoundswas >95% and was reproducible. The within- and between-day variability of the assay was <3% throughout the examined concentration range. Plasma Protein Binding Study-The study was conducted to test whether CM (at the concentrations of either 30 or 60 pg/mL) affects the binding of FT to plasma protein. Blank blood was obtained by carotid artery puncture, and the plasma was prepared by centrifugation (6000 x g for 10 min) at room temperature. Equilibrium dialysis was performed at room temperature for 15 h31 with a semipermeable membrane (type 18/32;Visking Company, Chicagu, IL) against isotonic Tris-HC1buffer (pH 7.4).FT and CM were added to the plasma chamber side to achieve final concentrations of 50 pg/mL for FT and 30 or 60 pg/mL for CM. Twenty microliters of the buffer was taken at 15 h and analyzed for FT by HPLC. Pharmacokinetic and Statistical Analysis-The pharmacokinetics of both FT and CM could be described by a two-compartment open model. The plasma data was fitted to the equation of the model with the aid of nonlinear regression program MULTI.32 Pharmacokinetic parameters [total plasma clearance (CL,), distribution volume at steady state (Vd,,), and mean residence time (MRT)] of FT following iv injection to the rats receiving CM infusion were calculated as follows:
CLt = Dose/AUC
(1)
VD,,= Dose * AUMC/AUC2
(2)
MRT = AUMC/AUC
(3)
Results and Discussion Plasma disappearance curves of FT (5,lo-, and 2O-mg/kg dose) with or without CM infusion are shown in Figures 1-3. In the control rats (without CM infusion), the plasma disposition of FT and its major metabolite, p-hydroxy FT, followed a classical drug-metabolite profile irrespective of FT dose. The plasma pharmacokinetics of FT could be best described by the conventional two-compartment open model. The plasma disappearance of FT was significantly retarded by the CM infusion and, as a result, the plasma concentrations of FT were greatly elevated. Most surprisingly, the p-hydroxy FT level in the plasma of CM-infused rats was so low (below the detection limit of 1 pg/mL) that it was not detectable during the experimental period irrespective of the FT doses of 5,10, and 20 mgkg. However, the two C,, values of plasma CM did not differ significantly in the effect on the disposition of FT. Table I summarizes the effect of the CM infusion at two different rates on the pharmacokinetic parameters of FT. The C,, of CM following CM infusion was successfully kept constant at either -30 or 60 pg/mL during the experimental period. The C,, was not affected by the dose of FT injected; thus, the results were expressed (Table I) as mean f SD of all the studies for three FT doses. In the control rats, FT showed linear pharmacokinetics: there was no dose dependency in the tIl2, CL,,Vd,,,and MRT in the range of FT doses examined. However, the pharmacokinetic parameters (except CLJ were changed by the CM infusion in an FT dose-dependent manner. At a low dose (5 mg/kg) of FT, the tl12and MRT of FT were increased significantly without significant Vd,,change. The MRT was increased fourfold and, as a consequence, the CL, of FT was decreased to one-fourth by the CM infusion. Although the CM infusion affected these pharmacokinetic parameters of FT, the effect of different C,, of CM on these Parameters was not statistically different. This result indicates that the plasma C,, level of -30 pg/mL is sufficient to
In eqs 1 3 , AUC and AUMC denote area under the plasma FT concentration-time curve from time zero to infinity and area under the first moment of the plasma FT concentration-time curve from time zero to infinity, respectively. The AUC and AUMC were calculated by the trapezoidal method from 0 to 120 min and an extrapolation from 120 min to infinity with the elimination rate constant (B). The plasma half-life (tl,.Jof FT was calculated by eq 4:
To compare the means of pharmacokinetic parameters from control and CM-treated groups, a two-way ANOVA was used. A p value of ~0.05was considered to be statistically significant throughout the analysis. All results are expressed as mean f SD:
Flgure 1-Mean ( 2 SD;n = 6) plasma concentration-time profiles of FT and phydroxy FT following bolus iv administration of FT at a dose of 5 mg/kg with or without co-infusion of CM. Key: (0)FT in saline-infused (control) group; (0)phydroxy FT in saline-infused (control) group; (A) FT in CM-infused group (C, = 30 pg/mL); (A) FT in CM-infused group (C,, = 60 pg/rnL). Journal of Pharmaceutical Sciences/ 953 Vol. 82, No. 9, September 1993
Table I-Effect of CM Infusion on the Pharmacoklnetlc Parameters of FT In Rats.
Fr
Dose, mglkg 5
10
20
Parameter f,,2, min
Without cM
With CM at
, C (pg/mL) of:
(Control)b
32.5 f 4.2
58.5 f 4.8
48.1 f 2.1
CL,, mUmin/kg 7.2 f 0.3 Vd,,, mUkg 281.5 f 11.2 MRT, min 38.6 f 2.7 47.2 f 1.3 f,,2, min 6.9 f 0.2 CL,, mL/min/kg 280.6 2 18.3 Vd,, mUkg MRT, min 40.0 f 1.8 f,,*, min 46.5 f 1.8 7.6 f 0.2 CL,, mL/min/kg Vd,,, mUkg 272.9 f 11.7 MRT, min 37.1 f 1.2
86.7 f 4.5' 90.8 f 5.1' 1.7 f 0.4' 1.7 f 0.4' 260.7 f 18.4 250.9 f 30.1 150.6 f 10.3' 150.3 f 14.3' 85.3 f 4.2' 49.5 f 3.1 3.2 f 0.3' . 2.2 f 0.3' 182.6 f 12.3' 220.4 2 19.2' 102.9 f 7.2" 57.5 f 5.0' 52.0 f 2.3 53.2 2 2.8 2.3 f 0.4' 2.4 f 0.3' 163.0 f 19.1' 168.3 f 36.4' 68.2 f 5.8' 74.2 2 8.1'
a Expressed as mean f SD of six experiments. Saline without CM was infused. Significantly different from the respective control group (p c 0.005). Significantly different from the respective control group (p c 0.01).
'
60
120
=(&.I Flgure 2-Mean (fSD; n = 6) plasma concentration-time profiles of FT and phydroxy FT following bolus iv administration of FT at a dose of 10 mg/kg with or without co-infusion of CM. For symbols, see Figure 1.
I
60
I
120
=(*.I Flgure &Mean (fSD; n = 6) plasma concentration-time profilesof FT and phydroxy FT following bolus iv administration of FT at a dose of 20 mg/kg with or without co-infusion of CM. For symbols, see Figure 1.
induce the drug interaction with FT. At higher doses of FT (10 and 20 m a ) , the t1,2,CL,, and MRT values of FT were also changed in a similar manner by the CM infusion. However, as 954 I Journal of Pharmaceutical Sciences Vol. 82, No. 9, September 1993
the dose of FT becomes higher, the increase in t1,2and MRT and the decrease in the CL, induced by the CM infusion became less significant. But, on the contrary to the case of lower FT dose (5 mg/kg), the Vd,, of FT was decreased significantly by the CM infusion at higher FT doses. Here again, the two levels of plasma CM did not d e c t these parameters of FT differently. The FT dose-dependent,but CM level-independent change in these pharmacokinetic parameters of FT are of great interest. The binding of FT to plasma protein was unaffected by the presence of CM: the percent of bound FT in the plasma of the control rats was 85.0 ? 2.4 (mean ? SD, n = 61, which is consistent with the previous report,31 and was 90.0 2 4.4 and 84.7 ? 2.3 at C,, of values 30 and 60 pg/mL, respectively. Therefore, the decrease in Vd,,of FT in the presence of CM could not be explained in terms of binding to plasma protein. Decreased binding of FT to body tissues might be an explanation. However, there is no evidence available at present to support tissue binding or its change by the CM infusion. More studies should be performed to elucidate the exact source of the Vd,,change. Regardless of the source of the Vd,,change, our data clearly indicate that CM interferes with the elimination of FT: The CL, of FT was decreased to one-half or one-fourth of the control value by the CM infusion. The two C,, levels of CM (30 and 60 pdmW exerted a similar effect on the CL, of FT. Besides, the CL, change was independent of the FT dose, which is contrary to the case of the other pharmacokinetic parameters. The decrease in the CL, of FT by the CM infusion was also supported by the absence of the major metabolite, p-hydroxy FT, in the plasma of the rats (Figures 1-3). No remarkable peaks except FT appeared in the HPLC chromatograms of the plasma samples from the CM-infused rats, implying the absence of any compensatory metabolic pathway of FT other than hydroxylation. The available evidence indicates that CM binds to cytochrome P-450 via its imidazole ring structure, thereby reducing the interaction between P-450 and other substrates.33 Because of the binding of CM to P-450, phase I metabolic reactions, such as hydroxylation, will be impaired, but the P-450-independent reactions, such as glucuronidation, may be spared.26-27,33 Because the hydroxylation occupies almost 90% of the metabolic pathway of FT,9 blockade of the hydroxylation may mean the blockade of metabolism itself. The absence of detectable p-hydroxy FT in the plasma of the CM-infused rats seems to reflect that FT metabolism (hydroxylation) wag completely inhibited
by the CM infusion. The decrease in the CL, of FT by CM could be attributed to the inhibition of the metabolism by CM.24-27 More direct and comprehensive studies including an in vitro metabolism study with hepatic microsomes are needed before any conclusion on the mechanism of the CM-FT interaction is made. Feely et d.20 have reported that the acute CM administration T caused 25% decrease in liver blood flow. However, assuming I is mainly eliminated by hepatic metabolism,94 FT is not a high clearance drug. Therefore, changes in hepatic blood flow would not d e c t the CL, of E"r significantly. Moreover, a 25% decrease of hepatic blood flow may not be sufficient to explain the threeto fourfold difference in the CL,. In conclusion, our data show that co-administration of CM changes the pharmacokinetics of FT dramatically: CM delayed the elimination of FT significantly, probably through inhibition of hydroxylation of FT. This hypothesis is supported by the absence ofp-hydroxy FT, a major metabolite of FT, in the plasma. In clinical settings, if CM is coadministered, the magnitude of difference in the pharmacokinetics of FT caused by CM may warrant dose adjustment of FT to avoid toxic effects of FT.
References and Notes 1. Brown, K.;Cavalla, J. F.; Green, D.; Wilson, H. B. Nature 1968, 219,164-167. 2. Brown, K.;Cater, D. P.; Cavalla, J. F.; Green, R. A. J. Med. Chem. 1974,17,1177-1181. 3. Katona, G.; Bondani, A. Cum. Med. Res. Opin. 1979,6,Suppl. 2, 71-78. 4. Famaey, J. P.; Ginsberg, F. Cum. Med. Res. Opin. 1983, 8, 675-681. 5. Wielandts, L.;Dequeker, J. Curr. Med. Res. Opin. 1979,6,Suppl. 2,85-89. 6. Rugginenti, A.Med. Sport 1980,33,117-124. 7. Antognetti, R.Minerva Ortoped. 1978,29,241-248. 8. Dowell, P. S. Xenobwtica 1984,14,947-953. 9. Franklin, R.A.; Norris, R.; Shepherd, N. W.;Rhenius, S. T. Xenobiotica 1984,12,955-960. 10. Dowell, P. S. Analyst 1983,108, 1535-1537.
11. Welch, R.W.; Bentek, H. L.; Harris,S. C. Gastroenterology1978, 74,459463. 12. MacKercher, P. A.; Ivy, K.J.; Baskin, W. N.; Krause, W. J. Ann. Intern. Med. 1977,87,676. 13. Freston. J. W. GaPtroenteroloev 1978.74.426-430. 14. Binder,'H. J.; Cocoa, A.; Crozley, R:J. ktroenterology 1978, 74. 380388. 15. La B m y , J. S.; Misciwicz, J.; Edward, J. Gut 1979,20,892-895. 16. Wesdrop, E.;Bartelman, J.; Pape, K. Gastroenterology 1978,74, 821-824. 17. Roberts, R. K.;Grice, J.; Wood, L.; Petroff, V.; McGuffie, C. Gastroenterology 1981,81,19-21. 18. Klotz, U.;Reimann, I. N. Engl. J. Med. 1980,302,1012-1014. 19. Patwardhan, R.; Johnson, R.; Shechan, J.;Desmond, P.; Wilkinson, G.; Hoyumpa, A; Branch, R.; Shenker, S. Gastroenterology 1981,80.1344. 20. Feely, J.; Wilkinson, G. R.; Wood, A. J. N. Engl. J. Med. 1981, 304,692-695. 21. Serhn, M. J.; Sibeon, R. G.; Mossman, S.; Breckrenrid A. M.; Williams, J. R. B.; Atwood, J. L.; Willoughby, J. M. !?Lancet 1979,2,317-319. 22. Neuvonen, P. J.; Tokola, R. A.; b t e , M. Eur. J. Clin. Phurmacol. 1981,21,215-220. 23. Fruncillo, R.J.; DiGregorio, G. J.; Soll, A. J. Phurm. Sci. 1983, 72,826-828. 24. Puurenen, J.; Sotaniemi, E.; Pelkonen, 0. Eur. J. Clin. Pharmacol. 1980,18,185-187. K. P.; Patwardhen, R. V.; Avant, G. R.; Mitchell, M. C.; 25. r, S. Gastroenterology 1981,80,1344. 26. Knodell, R. G.;Holtzmann, J. L.; Crankshaw, D. L.; Steele, N. M.; Stanley, L.N. Gastroenterology 1982,82,84-88. 27. Wilkinson, C. F.; Hetnarski, K.;Hicks, L. J. Pest. Biochem. Physwl. 1974,4,299-312. 28. Khoury, W.; Geraci, K.; Askari, A.; Johnson, M. Gastroenterology 1979,76,1169. 29. Fairfax, A. J.; Adam, J.; Pagan, K. S. Br. Med. J. 1978,1, 820. 30. Boutagy, J.;More, D. G.; Munro, I. A.; Schenfield, G. M. J. Lip. Chromatogr. 1984,7, 1651-1664. 31. Fumero, S.;Mondini, A.; Silvestri, S.; Zanolo, G. Pharm. Res. Comm. 1980.12.4148. 32. Yamaoka, K:; TAgawara, Y.; Nakagawa, T.;Uno, T.J. Phurm. l b n . 1981,4,87-85. 33. Somogyi, A.;.Gugler, R. Clin. Pharmacokinet. 1982,7,23-41. 34. Zanolo, G.;Giachetti, S.; Mondino, A.; Silvestri, S. Arzneim.Forsch.lDrug Res. 1980,31,109S1104.
ZK&
Journal of Pharmaceutical SciencesI 955 Vol. 62, No. 9, September 1993