Clinical use of clopidogrel in acute coronary syndrome

Population pharmacokinetic-pharmacodynamic modeling of clopidogrel for dose regimen optimization based on CYP2C19 phenotypes: A proof of concept study

Clopidogrel is an antiplatelet drug used to reduce the risk of acute coronary syndrome and stroke. It is converted by CYP2C19 to its active metabolite; therefore, poor metabolizers (PMs) of CYP2C19 exhibit diminished antiplatelet effects. Herein, we conducted a proof-of-concept study for using population pharmacokinetic-pharmacodynamic (PK-PD) modeling to recommend a personalized clopidogrel dosing regimen for individuals with varying CYP2C19 phenotypes and baseline P2Y12 reaction unit (PRU) levels. Data from a prospective phase I clinical trial involving 36 healthy male participants were used to develop the population PK-PD model predicting the concentrations of clopidogrel, clopidogrel H4, and clopidogrel carboxylic acid, and linking clopidogrel H4 concentrations to changes in PRU levels. A two-compartment model effectively described the PKs of both clopidogrel and clopidogrel carboxylic acid, and a one-compartment model of those of clopidogrel H4. The CYP2C19 phenotype was identified as a significant covariate influencing the metabolic conversion of the parent drug to its metabolites. A PD submodel of clopidogrel H4 that stimulated the fractional turnover rate of PRU levels showed the best performance. Monte Carlo simulations suggested that PMs require three to four times higher doses than extensive metabolizers to reach the target PRU level. Individuals within the top 20th percentile of baseline PRU levels were shown to require 2.5-3 times higher doses than those in the bottom 20th percentile. We successfully developed a population PK-PD model for clopidogrel considering the impact of CYP2C19 phenotypes and baseline PRU levels. Further studies are necessary to confirm actual dosing recommendations for clopidogrel.

Physician and Hospital Utilization of P2Y12 Inhibitors in ST-Segment–Elevation Myocardial Infarction in the United States

Background:

Ticagrelor and prasugrel are potent P2Y12 inhibitors with superior efficacy compared with clopidogrel among patients with ST-segment–elevation myocardial infarction (STEMI), though use in recent practice is not well described. In this retrospective study, we assessed trends, predictors, and variation in use of P2Y12 inhibitors in patients with STEMI in the United States.

Methods and Results:

We identified 169 505 STEMI patients in the Chest Pain-Myocardial Infarction Registry from October 2013 through March 2017. We determined national utilization rates of P2Y12 inhibitors at discharge, patient predictors for each medication, and variation in use between hospitals. In a subset of 9655 Medicare patients ≥65 years old, we compared 1-year adjusted risks of death, myocardial infarction, stroke, and bleeding based on hospital quartile of potent P2Y12 inhibitor use. Rates of ticagrelor use increased from 18.0% to 44.0%, while rates of prasugrel and clopidogrel use decreased from 24.6% to 13.5% and 57.4% to 42.6%, respectively. Prior percutaneous coronary intervention was the strongest clinical predictor for use of ticagrelor (adjusted odds ratio, 1.13 [95% CI, 1.09–1.18]) and prasugrel (adjusted odds ratio, 1.27 [95% CI, 1.21–1.34]) compared with clopidogrel. Predictors of clopidogrel use included no insurance, insurance with Medicare or Medicaid, and features associated with higher bleeding risk. The median hospital usage rate for newer P2Y12 inhibitors was 51.3% (interquartile range, 35.0%–65.9%), with substantial variation between hospitals (adjusted median odds ratio, 2.92 [95% CI, 2.77–3.10]). Among patients ≥65 years old, there were no differences in adjusted 1-year risks of adverse outcomes across hospital quartiles of potent P2Y12 inhibitor use.

Conclusions:

Almost one-half of STEMI patients by 2017 were discharged on ticagrelor while far fewer received prasugrel. Patient characteristics are associated with P2Y12 inhibitor selection, though substantial hospital variation exists. Identifying barriers to use of more potent P2Y12 inhibitors may improve patient-centered decision-making for STEMI patients.

Influence of statin treatment on pharmacokinetics and pharmacodynamics of clopidogrel and its metabolites in patients after coronary angiography/angioplasty

Possible interaction between clopidogrel and CYP3A4-metabolised atorvastatin or non-CYP3A4-metabolised rosuvastatin was investigated based on pharmacokinetic parameters of clopidogrel and its metabolites as well as the platelet reactivity test in patients undergoing coronary angiography/angioplasty. The study involved 50 patients (62.7 ± 7.8 years old) who underwent coronary angiography/angioplasty and were treated with clopidogrel and atorvastatin or rosuvastatin during the six months after the procedure. The P2Y12 reaction units (PRU) and pharmacokinetic parameters of clopidogrel, diastereoisomers of thiol metabolite (inactive H3 and active H4), and inactive carboxylic metabolite were measured 12-18 h and six months after the coronary angiography/angioplasty. There were no significant differences in concentrations of clopidogrel and its metabolites including the H4 active metabolite in plasma of patients co-treated with clopidogrel and atorvastatin or rosuvastatin. The use of statins did not affect the pharmacokinetic parameters of the studied compounds. A significant correlation was found between the C_max and AUC_0-t of the active H4 isomer and platelet aggregation in a group of patients treated with rosuvastatin but not in the atorvastatin group. No significant differences in PRU values were observed between the atorvastatin and rosuvastatin groups at the beginning of the study (171.4 ± 54.3 vs 146.3 ± 48.1 PRU, p = 0.192) as well as at six months (173.7 ± 45.8 vs 157.3 ± 54.9 PRU, p = 0.562). However, in a small group of patients, who were discharged from atorvastatin to rosuvastatin, an increase in the PRU values accompanied by a decreased AUC of the H4 active isomer was observed. The study confirmed that the systemic exposure to clopidogrel and its active H4 isomer of thiol metabolite, as well as the antiplatelet effect of the drug, were not negatively affected by co-administration of atorvastatin as compared with rosuvastatin.

Cilostazol reduces PAC-1 expression on platelets in ischemic stroke

BACKGROUND AND PURPOSE

Cilostazol, a phosphodiesterase III inhibitor, is known to be a useful antiplatelet agent that inhibits the progression of atherosclerosis in ischemic stroke. This study investigated the effects of combining cilostazol with aspirin on the expressions of P-selectin and PAC-1 on activated platelets in acute ischemic stroke.

METHODS

We analyzed 70 patients with acute ischemic stroke (<72 hrs of an ischemic event). The daily intake was 100 mg of aspirin in 37 patients and 100 mg of aspirin plus 200 mg of cilostazol in 33 patients. The expressions of P-selectin and PAC-1 on activated platelets were measured on the day of admission and 5 days later. We also evaluated the clinical progression using the National Institutes of Health Stroke Scale (NIHSS) at the same times.

RESULTS

After 5 days the extent of PAC-1 expression on activated platelets was significantly lower for combined aspirin and cilostazol treatment (61.0+/-19.3%, p=0.008; mean+/-standard deviation) than the baseline level (70.9+/-12.9%), but did not differ between aspirin alone (66.0 +/-19.0%) and baseline (70.1+/-15.7%). The expression of P-selectin did not differ between combined aspirin and cilostazol treatment and baseline. The clinical progression did not differ between the two groups, as indicated by the absence of significant changes on the NIHSS in the acute period.

CONCLUSIONS

This study found that the combined regimen of aspirin and cilostazol exerts the beneficial effect of reducing PAC-1 activity on activated platelets in acute ischemic stroke. However, the clinical outcome of this regimen was no better than that of the aspirin-only regimen. Therefore, further detailed studies of the possible clinical benefits of cilostazol in acute ischemic stroke are needed.