The Effect of St John's Wort on the Pharmacodynamic Response of Clopidogrel in Hyporesponsive Volunteers and Patients: Increased Platelet Inhibition by Enhancement of CYP3A4 Metabolic Activity
Cardiovascular Center, Department of Anesthesiology, University of Michigan, Ann Arbor, MI 48109-5861, USA. Journal of cardiovascular pharmacology
(Impact Factor: 2.14).
10/2010; 57(1):86-93. DOI: 10.1097/FJC.0b013e3181ffe8d0
Clopidogrel is metabolically activated by cytochrome P450 (CYP) isoenzymes. We evaluated whether St. John's wort (SJW), a CYP2C19 and CYP3A4 inducer, enhances the pharmacodynamic response of clopidogrel. Volunteers (n = 45) were screened for clopidogrel hyporesponsiveness after a 300-mg load. After a 7-day washout, hyporesponders (n = 10) received 14 days of SJW (300 mg 3 times a day) followed by a second 300-mg clopidogrel. Platelet aggregation was measured at 0, 2, 4, and 6 hours postloading; hepatic CYP3A4 activity was simultaneously determined at 0 and 4 hours by the erythromycin breath test. A prospective, randomized, double-blind pilot study was conducted in postcoronary stent patients (n = 85) on clopidogrel 75 mg/d screened for clopidogrel hyporesponsiveness. Hyporesponders (n = 20) were randomized to SJW (n = 10) or placebo (n = 10); platelet aggregation was measured before and after 14 days of therapy. In volunteers, SJW decreased platelet aggregation (59% ± 14% vs. 40% ± 15% at 2 hours, P = 0.02; 56% ± 10% vs. 44% ± 13% at 4 hours, P < 0.03; and 55% ± 14% vs. 37% ± 14% at 6 hours, P = 0.01) and increased CYP3A4 activity (2.1% ± 0.4% CO2 exhaled per hour before vs. 2.9% ± 0.6% CO2 exhaled per hour after SJW, P = 0.002). In patients, SJW decreased platelet reactivity (226 ± 39 vs. 185 ± 49 P2Y12 reactivity units, P = 0.0002) and increased platelet inhibition (23% ± 11% vs. 41% ± 16%, P = 0.002). SJW may be a future therapeutic option to increase CYP metabolic activity and antiplatelet effect of clopidogrel in hyporesponders.
Available from: Jeffrey A Breall
- "However, CYP2C19 metabolic status alone was found to account for only 12% of the variability in clopidogrel response.8 Several lines of evidence suggest that the CYP3A4 and CYP3A5 enzymes may play a role in clopidogrel activation, although data are not uniform.1,5,9,10CYP3A5*3 polymorphism has not been shown to significantly predict clopidogrel pharmacokinetics.8,11,12 "
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ABSTRACT: Recent candidate gene studies using a human liver bank and in vivo validation in healthy volunteers identified polymorphisms in cytochrome P450 (CYP) 3A4 gene (CYP3A4*22), Ah-receptor nuclear translocator (ARNT), and peroxisome proliferator-activated receptor-α (PPAR-α) genes that are associated with the CYP3A4 phenotype. We hypothesized that the variants identified in these genes may be associated with altered clopidogrel response, since generation of clopidogrel active metabolite is, partially mediated by CYP3A activity. Blood samples from 211 subjects, of mixed racial background, with established coronary artery disease, who had received clopidogrel, were analyzed. Platelet aggregation was determined using light transmittance aggregometry (LTA). Genotyping for CYP2C19*2, CYP3A4*22, PPAR-α (rs4253728, rs4823613), and ARNT (rs2134688) variant alleles was performed using Taqman® assays. CYP2C19*2 genotype was associated with increased on-treatment platelet aggregation (adenosine diphosphate 20 μM; P=0.025). No significant difference in on-treatment platelet aggregation, as measured by LTA during therapy with clopidogrel, was demonstrated among the different genotypes of CYP3A4*22, PPAR-α, and ARNT. These findings suggest that clopidogrel platelet inhibition is not influenced by the genetic variants that have previously been associated with reduced CYP3A4 activity.
Available from: PubMed Central
- "In a small prospective study, administration of St John's wort enhanced the platelet inhibitory effect of clopidogrel in volunteers known to be unresponsive to the drug and in patients with stable coronary artery disease . Their further studies suggested that St John's wort on the pharmacodynamic response of clopidogrel in hyporesponsive volunteers and patients could increase platelet inhibition by enhancement of CYP3A4 metabolic activity . Our study showed that BNC showed obvious increase effect on the catalytic activities of drug metabolism CYP2C19 enzyme. "
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ABSTRACT: The effects of Buchang Naoxintong Capsules (BNCs) on S-mephenytoin 4'-hydroxylation activities in human liver microsomes in vitro were assessed. Human liver microsome was prepared by different ultracentrifugation. Human liver microsome incubation experiment was carried out to assay BNC on S-mephenytoin 4'-hydroxylation activities. The 4'-hydroxylation of S-mephenytoin, a representative substrate toward CYP2C19, was increased by phenytoin sodium (positive control). After the incubation, the metabolites of the substrates (4'-OH-mephenytoin) were determined by HPLC. Results showed that both phenytoin sodium and BNC showed obvious increase effect on CYP2C19. The enzymatic reaction of BNC was observed with concentrations ranging from 5 μg/mL to 250 μg/mL. Compared to blank, the increase effect of BNC showed significant difference from the beginning of concentration of 150 μg/mL (P < 0.001). The conclusion was that BNC showed obvious increase effect on the catalytic activities of drug-metabolising CYP2C19 enzyme.
Available from: Pius Fasinu
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