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Choi JS, Yang JS, Choi DH. Effects of Ticlopidine on the Pharmacokinetics of Diltiazem and Its Main Metabolite, Desacetyldiltiazem, in Rats. Biomol Ther (Seoul) 2011. [DOI: 10.4062/biomolther.2011.19.2.255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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Schwartz JI, Agrawal NGB, Hartford AH, Cote J, Hunt TL, Verbesselt R, Eckols DR, Gottesdiener KM. The effect of etoricoxib on the pharmacodynamics and pharmacokinetics of warfarin. J Clin Pharmacol 2007; 47:620-7. [PMID: 17442687 DOI: 10.1177/0091270007299758] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The effects of etoricoxib on pharmacodynamic and pharmacokinetic parameters of warfarin were determined in healthy men and women. Subjects titrated with warfarin to an international normalized ratio for prothrombin time of 1.4 to 1.7 during a 28-day prestudy period were randomly assigned in crossover fashion to be coadministered etoricoxib (120 mg) or matching placebo over two 21-day continuous periods. On day 21, a 24-hour pharmacokinetic profile of both S(-) and R(+) warfarin, as well as international normalized ratio values, were determined. Etoricoxib increased the international normalized ratio by 13% (90% confidence interval: 8%, 19%; P </= .001). Etoricoxib had no effect on the pharmacokinetics of S(-) warfarin but led to a modest increase in the AUC(24 h) ( approximately 10%) of R(+) warfarin. This increase in the international normalized ratio is not likely to be clinically important in most patients; however, the international normalized ratio of patients coadministered oral anticoagulants and etoricoxib should be closely monitored, particularly during initiation of therapy.
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Affiliation(s)
- Jules I Schwartz
- Clinical Pharmacology, Merck Research Laboratories, Rahway, NJ 07065-0900, USA.
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Jaquenoud Sirot E, van der Velden JW, Rentsch K, Eap CB, Baumann P. Therapeutic Drug Monitoring and Pharmacogenetic Tests as Tools in Pharmacovigilance. Drug Saf 2006; 29:735-68. [PMID: 16944962 DOI: 10.2165/00002018-200629090-00001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Therapeutic drug monitoring (TDM) and pharmacogenetic tests play a major role in minimising adverse drug reactions and enhancing optimal therapeutic response. The response to medication varies greatly between individuals, according to genetic constitution, age, sex, co-morbidities, environmental factors including diet and lifestyle (e.g. smoking and alcohol intake), and drug-related factors such as pharmacokinetic or pharmacodynamic drug-drug interactions. Most adverse drug reactions are type A reactions, i.e. plasma-level dependent, and represent one of the major causes of hospitalisation, in some cases leading to death. However, they may be avoidable to some extent if pharmacokinetic and pharmacogenetic factors are taken into consideration. This article provides a review of the literature and describes how to apply and interpret TDM and certain pharmacogenetic tests and is illustrated by case reports. An algorithm on the use of TDM and pharmacogenetic tests to help characterise adverse drug reactions is also presented. Although, in the scientific community, differences in drug response are increasingly recognised, there is an urgent need to translate this knowledge into clinical recommendations. Databases on drug-drug interactions and the impact of pharmacogenetic polymorphisms and adverse drug reaction information systems will be helpful to guide clinicians in individualised treatment choices.
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Desta Z, Zhao X, Shin JG, Flockhart DA. Clinical significance of the cytochrome P450 2C19 genetic polymorphism. Clin Pharmacokinet 2002; 41:913-58. [PMID: 12222994 DOI: 10.2165/00003088-200241120-00002] [Citation(s) in RCA: 584] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cytochrome P450 2C19 (CYP2C19) is the main (or partial) cause for large differences in the pharmacokinetics of a number of clinically important drugs. On the basis of their ability to metabolise (S)-mephenytoin or other CYP2C19 substrates, individuals can be classified as extensive metabolisers (EMs) or poor metabolisers (PMs). Eight variant alleles (CYP2C19*2 to CYP2C19*8) that predict PMs have been identified. The distribution of EM and PM genotypes and phenotypes shows wide interethnic differences. Nongenetic factors such as enzyme inhibition and induction, old age and liver cirrhosis can also modulate CYP2C19 activity. In EMs, approximately 80% of doses of the proton pump inhibitors (PPIs) omeprazole, lansoprazole and pantoprazole seem to be cleared by CYP2C19, whereas CYP3A is more important in PMs. Five-fold higher exposure to these drugs is observed in PMs than in EMs of CYP2C19, and further increases occur during inhibition of CYP3A-catalysed alternative metabolic pathways in PMs. As a result, PMs of CYP2C19 experience more effective acid suppression and better healing of duodenal and gastric ulcers during treatment with omeprazole and lansoprazole compared with EMs. The pharmacoeconomic value of CYP2C19 genotyping remains unclear. Our calculations suggest that genotyping for CYP2C19 could save approximately 5000 US dollars for every 100 Asians tested, but none for Caucasian patients. Nevertheless, genotyping for the common alleles of CYP2C19 before initiating PPIs for the treatment of reflux disease and H. pylori infection is a cost effective tool to determine appropriate duration of treatment and dosage regimens. Altered CYP2C19 activity does not seem to increase the risk for adverse drug reactions/interactions of PPIs. Phenytoin plasma concentrations and toxicity have been shown to increase in patients taking inhibitors of CYP2C19 or who have variant alleles and, because of its narrow therapeutic range, genotyping of CYP2C19 in addition to CYP2C9 may be needed to optimise the dosage of phenytoin. Increased risk of toxicity of tricyclic antidepressants is likely in patients whose CYP2C19 and/or CYP2D6 activities are diminished. CYP2C19 is a major enzyme in proguanil activation to cycloguanil, but there are no clinical data that suggest that PMs of CYP2C19 are at a greater risk for failure of malaria prophylaxis or treatment. Diazepam clearance is clearly diminished in PMs or when inhibitors of CYP2C19 are coprescribed, but the clinical consequences are generally minimal. Finally, many studies have attempted to identify relationships between CYP2C19 genotype and phenotype and susceptibility to xenobiotic-induced disease, but none of these are compelling.
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Affiliation(s)
- Zeruesenay Desta
- Division of Clinical Pharmacology, Indiana University School of Medicine, Wishard Hospital, Indianapolis 46202, USA
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Ha-Duong NT, Dijols S, Macherey AC, Dansette PM, Mansuy D. Inhibition by ticlopidine and its derivatives of human liver cytochrome p450. Mechanism-based inactivation of CYP 2C19 by ticlopidine. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 500:145-8. [PMID: 11764927 DOI: 10.1007/978-1-4615-0667-6_18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- N T Ha-Duong
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Université René Descartes, CNRS UMR 8601, Paris, France
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Abstract
Warfarin is one of the most widely prescribed oral anticoagulants. However, optimal use of the drug has been hampered by its >10-fold interpatient variability in the doses required to attain therapeutic responses. Pharmacogenetic polymorphism of cytochrome P450 (CYP) may be associated with impaired elimination of warfarin and exaggerated anticoagulatory responses to the drug in certain patients. Clinically available warfarin is a racemic mixture of (R)- and (S)-warfarin, and the (S)-enantiomer has 3 to 5 times greater anticoagulation potency than its optical congener. Both enantiomers are eliminated extensively via hepatic metabolism with low clearance relative to hepatic blood flow. CYP2C9 is almost exclusively responsible for the metabolism of the pharmacologically more active (S)-enantiomer. Several human allelic variants of CYP2C9 have been cloned, designated as CYP2C9*1 (reference sequence or wild-type allele), CYP2C9*2, CYP2C9*3 and CYP2C9*4, respectively. The allelic frequencies for these variants differ considerably among different ethnic populations. Caucasians appear to carry the CYP 2C9*2 (8 to 20%) and CYP2C9*3 (6 to 10%) variants more frequently than do Asians (0% and 2 to 5%, respectively). The metabolic activities of the CYP2C9 variants have been investigated in vitro. The catalytic activity of CYP2C9*3 expressed from cDNA was significantly less than that of CYP2C9*1. Human liver microsomes obtained from individuals heterozygous for CYP2C9*3 showed significantly reduced (S)-warfarin 7-hydroxylation as compared with those obtained from individuals genotyped as CYP2C9*1. The influence of the CYP2C9*3 allele on the in vivo pharmacokinetics of (S)-warfarin has been studied in Japanese patients. Patients with the homozygous CYP2C9*3 genotype, as well as those with the heterozygous CYP2C9*1/*3 genotype, had significantly reduced clearance of (S)-warfarin (by 90 and 60%, respectively) compared with those with homozygous CYP2C9*1. The maintenance dosages of warfarin required in Japanese patients with heterozygous and homozygous CYP2C9*3 mutations were significantly lower than those in patients with CYP2C9*1/*1. In addition, 86% of British patients exhibiting adequate therapeutic responses with lower maintenance dosages of warfarin (<1.5 mg/day) had either the CYP2C9*2 or CYP2C9*3 mutation singly or in combination, whereas only 38% of randomly selected patients receiving warfarin carried the corresponding mutations. Furthermore, the former group showed more frequent episodes of major bleeding associated with warfarin therapy. These data indicate that the CYP2C9*3 allele may be associated with retarded elimination of (S)-warfarin and the resulting clinical effects. However, relationships between CYP2C9 genotype, enzyme activity, metabolism of probe substrates, dosage requirements and bleeding complications should be interpreted with caution, and further studies are required.
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Affiliation(s)
- H Takahashi
- Department of Pharmacotherapy, Meiji Pharmaceutical University, Kiyose, Tokyo, Japan.
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Ha-Duong NT, Dijols S, Macherey AC, Goldstein JA, Dansette PM, Mansuy D. Ticlopidine as a selective mechanism-based inhibitor of human cytochrome P450 2C19. Biochemistry 2001; 40:12112-22. [PMID: 11580286 DOI: 10.1021/bi010254c] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Experiments using recombinant yeast-expressed human liver cytochromes P450 confirmed previous literature data indicating that ticlopidine is an inhibitor of CYP 2C19. The present studies demonstrated that ticlopidine is selective for CYP 2C19 within the CYP 2C subfamily. UV-visible studies on the interaction of a series of ticlopidine derivatives with CYP 2C19 showed that ticlopidine binds to the CYP 2C19 active site with a K(s) value of 2.8 +/- 1 microM. Derivatives that do not involve either the o-chlorophenyl substituent, the free tertiary amine function, or the thiophene ring of ticlopidine did not lead to such spectral interactions and failed to inhibit CYP 2C19. Ticlopidine is oxidized by CYP 2C19 with formation of two major metabolites, the keto tautomer of 2-hydroxyticlopidine (1) and the dimers of ticlopidine S-oxide (TSOD) (V(max) = 13 +/- 2 and 0.4 +/- 0.1 min(-1)). During this oxidation, CYP 2C19 was inactivated; the rate of its inactivation was time and ticlopidine concentration dependent. This process meets the chemical and kinetic criteria generally accepted for mechanism-based enzyme inactivation. It occurs in parralel with CYP 2C19-catalyzed oxidation of ticlopidine, is inhibited by an alternative well-known substrate of CYP 2C19, omeprazole, and correlates with the covalent binding of ticlopidine metabolite(s) to proteins. Moreover, CYP 2C19 inactivation is not inhibited by the presence of 5 mM glutathione, suggesting that it is due to an alkylation occurring inside the CYP 2C19 active site. The effects of ticlopidine on CYP 2C19 are very analogous with those previously described for the inactivation of CYP 2C9 by tienilic acid. This suggests that a similar electrophilic intermediate, possibly a thiophene S-oxide, is involved in the inactivation of CYP 2C19 and CYP 2C9 by ticlopidine and tienilic acid, respectively. The kinetic parameters calculated for ticlopidine-dependent inactivation of CYP 2C19, i.e., t(1/2max) = 3.4 min, k(inact) = 3.2 10(-3) s(-1), K(I) = 87 microM, k(inact)/K(I) = 37 L.mol(-1).s(-1), and r (partition ratio) = 26 (in relation with formation of 1 + TSOD), classify ticlopidine as an efficient mechanism-based inhibitor although somewhat less efficient than tienilic acid for CYP 2C9. Importantly, ticlopidine is the first selective mechanism-based inhibitor of human liver CYP 2C19 and should be a new interesting tool for studying the topology of the active site of CYP 2C19.
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Affiliation(s)
- N T Ha-Duong
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR 8601 CNRS, Université Paris V, 45 Rue des Saints-Pères, 75270 Paris Cedex 06, France
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Ko JW, Desta Z, Soukhova NV, Tracy T, Flockhart DA. In vitro inhibition of the cytochrome P450 (CYP450) system by the antiplatelet drug ticlopidine: potent effect on CYP2C19 and CYP2D6. Br J Clin Pharmacol 2000; 49:343-51. [PMID: 10759690 PMCID: PMC2014930 DOI: 10.1046/j.1365-2125.2000.00175.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/1999] [Accepted: 01/04/2000] [Indexed: 11/20/2022] Open
Abstract
AIMS To examine the potency of ticlopidine (TCL) as an inhibitor of cytochrome P450s (CYP450s) in vitro using human liver microsomes (HLMs) and recombinant human CYP450s. METHODS Isoform-specific substrate probes of CYP1A2, 2C19, 2C9, 2D6, 2E1 and 3A4 were incubated in HLMs or recombinant CYPs with or without TCL. Preliminary data were generated to simulate an appropriate range of substrate and inhibitor concentrations to construct Dixon plots. In order to estimate accurately inhibition constants (Ki values) of TCL and determine the type of inhibition, data from experiments with three different HLMs for each isoform were fitted to relevant nonlinear regression enzyme inhibition models by WinNonlin. RESULTS TCL was a potent, competitive inhibitor of CYP2C19 (Ki = 1.2 +/- 0.5 microM) and of CYP2D6 (Ki = 3.4 +/- 0.3 microM). These Ki values fell within the therapeutic steady-state plasma concentrations of TCL (1-3 microM). TCL was also a moderate inhibitor of CYP1A2 (Ki = 49 +/- 19 microM) and a weak inhibitor of CYP2C9 (Ki > 75 microM), but its effect on the activities of CYP2E1 (Ki = 584 +/- 48 microM) and CYP3A (> 1000 microM) was marginal. CONCLUSIONS TCL appears to be a broad-spectrum inhibitor of the CYP isoforms, but clinically significant adverse drug interactions are most likely with drugs that are substrates of CYP2C19 or CYP2D6.
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Affiliation(s)
- J W Ko
- Division of Clinical Pharmacology, Departments of Medicine and Pharmacology, Georgetown University Medical Center, Washington DC 20007, USA
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Tateishi T, Kumai T, Watanabe M, Nakura H, Tanaka M, Kobayashi S. Ticlopidine decreases the in vivo activity of CYP2C19 as measured by omeprazole metabolism. Br J Clin Pharmacol 1999; 47:454-7. [PMID: 10233213 PMCID: PMC2014235 DOI: 10.1046/j.1365-2125.1999.00914.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS To examine the effect of ticlopidine administration on the activities CYP2C19 and CYP3 A in vivo using omeprazole as a model substrate. METHODS A single dose of 40 mg omeprazole was administered orally with or without ticlopidine (300 mg daily for 6 days) to six Japanese extensive metabolisers with respect to CYP2C19. Blood samples were taken for the measurement of plasma concentrations of omeprazole, 5-hydroxyomeprazole and omeprazole sulphone. RESULTS Ticlopidine administration increased omeprazole Cmax (1978+/-859/ 3442+/-569 (control phase/ticlopidine phase, nm )) and decreased the oral clearance of omeprazole (CL/F; 25.70+/-16. 17/10.76+/-1.16 (control phase/ticlopidine phase, l h-1 )) significantly. The 5-hydroxyomeprazole to omeprazole AUC ratio (0. 817+/-0.448/0.236+/-0.053 (control phase/ticlopidine phase)) and the 5-hydroxyomeprazole to omeprazole sulphone AUC ratio (1.114+/-0. 782/0.256+/-0.051 (control phase/ticlopidine phase)) were decreased significantly after ticlopidine administration. The decrease in omeprazole CL/F and the 5-hydroxyomeprazole to omeprazole AUC ratio correlated significantly with their respective absolute values when the drug was given alone. The decrease in CL/F following ticlopidine administration correlated with that in the 5-hydroxyomeprazole to omeprazole AUC ratio. CONCLUSIONS These findings suggest that ticlopidine inhibited the in vivo activity of CYP2C19, but not, or to a lesser extent CYP3 A4, and that the magnitude of inhibition by ticlopidine is related to the in vivo activity of CYP2C19 before inhibition.
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Affiliation(s)
- T Tateishi
- Department of Pharmacology, St Marianna University School of Medicine, Kanagawa, Japan
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Abstract
As many as half of the approximately 400,000 patients who undergo nonsurgical coronary artery procedures every year receive an intracoronary stent. To prevent thrombus formation within the stent, antiplatelet treatment with ticlopidine and aspirin is administered. Ticlopidine is known to cause cutaneous adverse reactions in up to 5.1% of patients, with a 3.4% discontinuation rate. However, published studies of patients receiving the drug to prevent subacute thrombosis after intracoronary stent placement report a frequency of rash ranging from 0.8-1.6%. We hypothesized that the frequency of rash in this patient population is underreported, and conducted a retrospective chart review, collecting data on frequency and severity of rash, treatment required, patient demographics, and concomitant drugs that may predispose patients to rash. The frequency of rash was approximately 7% in this group of patients.
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Affiliation(s)
- T R Whetsel
- Department of Clinical Pharmacy, School of Pharmacy, West Virginia University, Morgantown 26506, USA
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Abstract
OBJECTIVE To report a probable case of ticlopidine-induced phenytoin toxicity. CASE SUMMARY A 72-year-old white man suddenly developed combative behavior, refused to leave his room, stopped eating, and began falling to the floor 6 weeks after being given ticlopidine. The total phenytoin concentration was measured at 43.6 micrograms/mL; the dosage of phenytoin was decreased and the symptoms later resolved. After ticlopidine was discontinued, the patient was rechallenged with the same dose of phenytoin without symptoms of toxicity. DISCUSSION Possible mechanisms of the drug interaction are discussed with emphasis on cytochrome P450 metabolism. CONCLUSIONS Clinicians should be aware of this potentially serious drug interaction and either avoid the phenytoin-ticlopidine combination, or monitor closely for phenytoin toxicity.
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Affiliation(s)
- S L Klaassen
- Cognitive Pharmaceutical Services, Ottumwa, IA 52501, USA.
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Donahue SR, Flockhart DA, Abernethy DR, Ko JW. Ticlopidine inhibition of phenytoin metabolism mediated by potent inhibition of CYP2C19. Clin Pharmacol Ther 1997; 62:572-7. [PMID: 9390115 DOI: 10.1016/s0009-9236(97)90054-0] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A patient who had taken a stable dose of phenytoin for 2 years had a coronary stent placed for unstable angina and ticlopidine was added to his therapeutic regimen. Twenty-five days later, he was hospitalized with acute symptomatic phenytoin toxicity and a serum concentration of 46.5 micrograms/ml. Determination of metabolic genotype revealed that the patient had a wild-type genotype for CYP2C9, CYP2C19, and CYP2D6. Using human liver microsomes, we showed that ticlopidine is a potent inhibitor of cytochrome P450 2C19, with an estimated inhibition constant (Ki) of 3.7 +/- 0.2 mumol/L. The influence of ticlopidine on CYP2C9, the other cytochrome P450 isoform that metabolizes phenytoin, is relatively weak, with a calculated Ki of 38.8 +/- 27 mumol/L. These data suggest that, in this patient, phenytoin toxicity was caused by inhibition of CYP2C19 by ticlopidine, and the data emphasize the importance of CYP2C19 in the metabolism of phenytoin.
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Affiliation(s)
- S R Donahue
- Department of Medicine and Pharmacology, Georgetown University Medical Center, Washington, DC 20007, USA
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