Influence of statin treatment on platelet inhibition by clopidogrel - a randomized comparison of rosuvastatin, atorvastatin and simvastatin co-treatment

Changes in lipoproteins associated with lipid-lowering and antiplatelet strategies in patients with acute myocardial infarction

Background

Despite lipid-lowering and antiplatelet therapy, the pattern of residual lipoproteins seems relevant to long-term cardiovascular outcomes. This study aims to evaluate the effects of combined therapies, commonly used in subjects with acute myocardial infarction, in the quality of low-density lipoprotein (LDL) particles.

Methods

Prospective, open-label trial, included patients with acute myocardial infarction. Patients were randomized to antiplatelet treatment (ticagrelor or clopidogrel) and subsequently to lipid-lowering therapy (rosuvastatin or simvastatin/ezetimibe) and were followed up for six months. Nonlinear optical properties of LDL samples were examined by Gaussian laser beam (Z-scan) to verify the oxidative state of these lipoproteins, small angle X-ray scattering (SAXS) to analyze structural changes on these particles, dynamic light scattering (DLS) to estimate the particle size distribution, ultra violet (UV)-visible spectroscopy to evaluate the absorbance at wavelength 484 nm (typical from carotenoids), and polyacrylamide gel electrophoresis (Lipoprint) to analyze the LDL subfractions.

Results

Simvastatin/ezetimibe with either clopidogrel or ticagrelor was associated with less oxidized LDL, and simvastatin/ezetimibe with ticagrelor to lower cholesterol content in the atherogenic subfractions of LDL, while rosuvastatin with ticagrelor was the only combination associated with increase in LDL size.

Conclusions

The quality of LDL particles was influenced by the antiplatelet/lipid-lowering strategy, with ticagrelor being associated with the best performance with both lipid-lowering therapies. Trial registration: NCT02428374.

Impact of drug treatment and drug interactions in post-stroke epilepsy

Stroke is a huge burden on our society and this is expected to grow in the future due to the aging population and the associated co-morbidities. The improvement of acute stroke care has increased the survival rate of stroke patients, and many patients are left with permanent disability, which makes stroke the main cause of adult disability. Unfortunately, many patients face other severe complications such as post-stroke seizures and epilepsy. Acute seizures (ASS) occur within 1 week after the stroke while later occurring unprovoked seizures are diagnosed as post-stroke epilepsy (PSE). Both are associated with a poor prognosis of a functional recovery. The underlying neurobiological mechanisms are complex and poorly understood. There are no universal guidelines on the management of PSE. There is increasing evidence for several risk factors for ASS/PSE, however, the impacts of recanalization, drugs used for secondary prevention of stroke, treatment of stroke co-morbidities and antiseizure medication are currently poorly understood. This review focuses on the common medications that stroke patients are prescribed and potential drug interactions possibly complicating the management of ASS/PSE.

Clopidogrel drug interactions: a review of the evidence and clinical implications

INTRODUCTION

Patients with cardiovascular disease are commonly affected by a number of comorbidities leading to a high prevalence of polypharmacy. Polypharmacy increases the probability of drug-drug interactions (DDIs). Amongst these, DDIs involving clopidogrel, the most commonly utilized platelet P2Y₁₂ inhibitor, is a topic of potential clinical concern.

AREAS COVERED

This article reviews DDIs between clopidogrel and drugs which are widely used in clinical practice. In particular, drugs shown to interfere with the pharmacodynamic and pharmacokinetic effects of clopidogrel and the clinical implications of these findings are reviewed. These drugs include inhibitors of gastric acid secretion, statins, calcium channel blockers, antidiabetic agents, and antimicrobial agents. For the references, we searched PubMed, EMBASE, or the Cochrane Library.

EXPERT OPINION

Clopidogrel-drug interactions are common. Most of these DDIs are limited to laboratory findings showing an impact on clopidogrel-induced antiplatelet effects. While variability in clopidogrel-induced antiplatelet effects is known to affect clinical outcomes, with high platelet reactivity being associated with thrombotic complications among patients undergoing coronary stenting, most studies assessing the clinical implications of clopidogrel-drug interactions have not shown to significantly affect outcomes. However, awareness of these DDIs remains important for optimizing the selection of concomitant therapies.

Impact of genetic variants of selected cytochrome P450 isoenzymes on pharmacokinetics and pharmacodynamics of clopidogrel in patients co-treated with atorvastatin or rosuvastatin

PURPOSE

Impaired antiplatelet effect of clopidogrel (CLP) can result from drug-drug interactions and genetic polymorphisms of drug-metabolizing enzymes. The aim of the study was to evaluate the effect of genetic polymorphisms of ABCB1 and the selected cytochrome P450 isoenzymes on the pharmacodynamics and pharmacokinetics of CLP and its metabolites in patients co-treated with atorvastatin or rosuvastatin.

METHODS

The study involved 50 patients after coronary angiography/angioplasty treated with CLP and atorvastatin (n = 25) or rosuvastatin (n = 25) for at least 6 months. Plasma concentrations of CLP, diastereoisomers of thiol metabolite (inactive H3 and active H4), and inactive CLP carboxylic acid metabolite were measured by UPLC-MS/MS method. Identification of the CYP2C19*2, CYP2C19*17, CYP3A4*1G, CYP1A2*1F, and ABCB1 C3435T genetic polymorphisms was performed by PCR-RFLP, while platelet reactivity units (PRU) were tested using the VerifyNow P2Y12 assay.

RESULTS

There were significant differences in the pharmacokinetic parameters of the H4 active metabolite of CLP in the atorvastatin and rosuvastatin group divided according to their CYP2C19 genotype. There were no significant associations between CYP3A4, CYP1A2, and ABCB1 genotypes and pharmacokinetic parameters in either statin groups. In the multivariate analysis, CYP2C19*2 genotype and non-genetic factors including BMI, age, and diabetes significantly affected platelet reactivity in the studied groups of patients (P < 0.01). In the atorvastatin group, CYP2C19*2, CYP3A4*1G, and ABCB1 C3435T TT genotypes were independent determinants of PRU values (P < 0.01).

CONCLUSION

The CYP2C19*2 allele is the primary determinant of the exposition to the H4 active metabolite of clopidogrel and platelet reactivity in patients co-treated with atorvastatin or rosuvastatin.

Investigating the Effect of Demographics, Clinical Characteristics, and Polymorphism of MDR-1, CYP1A2, CYP3A4, and CYP3A5 on Clopidogrel Resistance

Clopidogrel is an antiplatelet agent that is indicated for cardiovascular emergencies and procedures. The drug, however, is subject to response variability leading to therapy resistance. In this research, we explored the demographic, clinical, and genetic factors associated with clopidogrel resistance. Data analysis among our 280 subjects receiving clopidogrel showed some risk factors that are significantly associated with clopidogrel resistance compared with responders. Those were: female sex (P = 0.021), advanced age (P = 0.011), obesity (P = 0.002), and higher body mass index (P = 0.008) and higher platelets count (P = 0.002). However, known polymorphisms of MDR-1, CYP1A2, CYP3A4, and CYP3A5 were not associated with treatment resistance when compared to responders to clopidogrel therapy. Knowledge about such risk factors might provide recommendation in the future about starting doses or monitoring recommendations.

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.

Statins significantly reduce mortality in patients receiving clopidogrel without affecting platelet activation and aggregation: a systematic review and meta-analysis

BACKGROUND

Combination of statins and clopidogrel is frequently administered in patients with coronary artery disease (CAD). They are mainly activated and eliminated in the liver by cytochrome P450 isoenzyme 3A4 (CYP3A4). The aim was to clarify whether the coadministration of clopidogrel and statins attenuate respective efficacy.

METHODS

PubMed, Embase, the Cochrane Library, Web of Science and Clinical Trials. gov were searched for until August 2018. Randomized controlled trials (RCTs) and cohort studies were taken into quality evaluation. Data were pooled using random effect models to estimate standard mean difference (SMD) or risk ratio (RR) with 95% confidence interval (CI).

RESULTS

In total, 28 studies representing 25,267 participants were included. Statins reduce the mortality of patients administered clopidogrel (RR 0.54; 95% CI 0.40,0.74; p = 0.000), no differences were found in platelet aggregation (PA) (SMD 0.02; 95% CI -0.38,0.42; p = 0.920) and the expressions of P-selectin (SMD -0.04; 95% CI -0.14,0.05; p = 0.346), CD40L (SMD 0.09; 95% CI -0.29,0.48; p = 0.633), CD63 (SMD 0.09; 95% CI -0.01,0.19; p = 0.079) and PAC-1 (SMD 0.03; 95% CI -0.08,0.13; p = 0.633). Furthermore, CYP3A4 metabolized or non-CYP3A4 metabolized statins have no discrepancies in PA (SMD 0.13; 95% CI -0.31,0.58; p = 0.556), P-selectin (SMD 0.17; 95% CI -0.16,0.51; p = 0310), death (RR 0.89; 95% CI 0.38,2.07; p = 0.791), except for triglyceride (TG) (SMD -0.19; 95% CI -0.33,-0.06; p = 0.005).

CONCLUSIONS

This meta-analysis confirmed that statins reduce mortality in patients undergoing clopidogrel treatment without affecting platelet activation and aggregation.

Effectiveness and Safety of Clopidogrel Co-administered With Statins and Proton Pump Inhibitors: A Korean National Health Insurance Database Study

Simultaneous competition for cytochrome P450 (CYP) 2C19 and CYP3A4 might diminish clopidogrel's antiplatelet effect by impacting its metabolic activation. This pharmacoepidemiologic study investigated whether proton pump inhibitors (PPIs) and CYP3A4-metabolized statins individually and jointly increase thrombotic events by attenuating clopidogrel's effectiveness. From Korean nationwide claims data (2007-2015), we selected 59,233 patients who initiated clopidogrel and statins after coronary stenting and compared thrombotic risks by PPI or CYP3A4-metabolized statin use or both. PPIs were associated with increased thrombotic risks (hazard ratio (HR) 1.27, 95% confidence interval (CI) 1.12-1.45), unlike CYP3A4-metabolized statins (HR 1.03, 95% CI 0.98-1.07). PPIs with high CYP2C19-inhibitory potential were more relevant than those with low potential (HR 1.28, 95% CI 1.02-1.61). Joint effects of PPIs and CYP3A4-metabolized statins were nonsignificant (relative excess risk due to interaction -0.14, 95% CI -0.34 to 0.07). Concurrent PPIs were associated with increased thrombotic risks in patients receiving clopidogrel and statins; CYP3A4-metabolized statins did not exacerbate PPI-associated risks.

Platelet function variability and non-genetic causes

Dual antiplatelet therapy (DAPT) has been established for the treatment of coronary artery disease, especially in and after acute coronary syndromes, and after coronary interventions. Data suggest that a significant percentage of individuals treated with clopidogrel do not receive the expected therapeutic benefit because of a decreased responsiveness of their platelets, which is caused by several extrinsic and intrinsic mechanisms. The clinical consequence of clopidogrel non-responsiveness is severe cardiovascular complications. Besides genetic variability in response to antiplatelet therapy, non-genetic causes such as drug interactions (proton-pump inhibitors, statins, calcium-channel blockers, coumarine derivates, antibiotics, antimycotics) and co-morbidities (diabetes mellitus, renal failure, obesity) are responsible for this phenomenon. Large clinical trials with standardised laboratory methods and hard clinical endpoints are needed to identify these interactions with clopidogrel and predictors for its non-responsiveness.

Clopidogrel non-responsiveness in patients undergoing percutaneous coronary intervention using the VerifyNow test: frequency and predictors

Objectives

Stent thrombosis and death after percutaneous coronary intervention (PCI) can be caused by a phenomenon known as clopidogrel non-responsiveness which has been shown to occur in approximately 5%–44% of patients. We investigated the responsiveness of clopidogrel in an Iraqi series of cases. Our aim was to determine for the first time the frequency and predictors of clopidogrel non-responsiveness among Iraqi patients with ischaemic heart disease undergoing PCI.

Methods

The study was conducted at the Cardiac Catheterization Center, Baghdad Teaching Hospital, Medical City, from January to May 2014, and included patients who presented for PCI. A platelet aggregation test was performed for those patients using the VerifyNow system.

Results

A total of 115 patients (mean age: 58.3±10.1 years; male sex: 73.9%) were included in the study. 18.3% of the study population were clopidogrel non-responders, which was comparable with the results of a Chinese study (20.28%, P=0.796) but contrasted with other reports from Jordan, Brazil and Thailand. The major independent predictive factor for non-responsiveness in our report was diabetes mellitus (OR 5.96, 95% CI 2.23 to 13.71; P=0.001), followed by hypertension (OR 4.135, P=0.035), obesity (OR 3.44, P=0.037) and male sex (OR 3.039, P=0.045). Previous use of clopidogrel (OR 0.17, P=0.02) and younger age (OR 0.72, P=0.026) were identified as protective factors.

Conclusions

In this study, 18.3% of patients were non-responders to clopidogrel and the major independent predictive factors for non-responsiveness were diabetes mellitus, hypertension, obesity and male sex.

Platelet reactivity in response to loading dose of atorvastatin or rosuvastatin in patients with stable coronary disease before percutaneous coronary intervention: The STATIPLAT randomized study

BACKGROUND

The acute effects of statin loading dose (LD) on platelet reactivity in patients with chronic stable angina (CSA) are not completely clear.

HYPOTHESIS

We hypothesized that LDs of atorvastatin and rosuvastatin have different pharmacodynamic acute effects on platelet aggregability in CSA patients with baseline normal platelet reactivity while on dual antiplatelet therapy (DAPT).

METHODS

From September 2011 to February 2014, all consecutive CSA patients on chronic DAPT (aspirin and clopidogrel) were evaluated before elective percutaneous coronary intervention (PCI). An initial assessment of platelet reactivity in response to thrombin receptor agonist, ADP, and ASP (respectively, indicative of the response to clopidogrel and aspirin) was performed with impedance aggregometry. Patients with high platelet reactivity to ADP test (area under the curve >47) were excluded. The remaining patients were randomized into 3 treatment groups: Group A, atorvastatin LD 80 mg; Group B, rosuvastatin LD 40 mg; and Group C, no statin LD (control group). A second assessment of platelet reactivity was performed ≥12 hours after statin LD.

RESULTS

682 patients were screened and 145 were randomized into the 3 groups. At baseline and after statin LD, no significant difference was found in platelet reactivity in response to 3 different agonists between the 3 groups. Subgroup analysis showed that platelet reactivity to ADP test was significantly lower in patients chronically treated with low-dose statins (n = 94) compared with statin-naïve patients (n = 51; 15.32 ± 1.50 vs 18.59 ± 1.30; P = 0.007).

CONCLUSIONS

Loading dose of atorvastatin (80 mg) or rosuvastatin (40 mg) did not induce significant variation in platelet reactivity in CSA patients with baseline reduced platelet reactivity as in chronic DAPT. Our data confirm that chronic concomitant treatment with low-dose statins and clopidogrel resulted in significantly lower platelet reactivity compared with clopidogrel alone.

Platelet tissue factor activity and membrane cholesterol are increased in hypercholesterolemia and normalized by rosuvastatin, but not by atorvastatin

BACKGROUND AND AIMS

High plasma LDL-cholesterol (LDL-C) and platelet responses have major pathogenic roles in atherothrombosis. Thus, statins and anti-platelet drugs constitute mainstays in cardiovascular prevention/treatment. However, the role of platelet tissue factor-dependent procoagulant activity (TF-PCA) has remained unexplored in hypercholesterolemia. We aimed to study platelet TF-PCA and its relationship with membrane cholesterol in vitro and in 45 hypercholesterolemic patients (HC-patients) (LDL-C >3.37 mmol/L, 130 mg/dL) and 37 control subjects (LDL-C <3.37 mmol/L). The effect of 1-month administration of 80 mg/day atorvastatin (n = 21) and 20 mg/day rosuvastatin (n = 24) was compared.

METHODS

Platelet TF-PCA was induced by GPIbα activation with VWF-ristocetin.

RESULTS

Cholesterol-enriched platelets in vitro had augmented aggregation/secretion and platelet FXa generation (1.65-fold increase, p = 0.01). HC-patients had 1.5-, 2.3- and 2.5-fold increases in platelet cholesterol, TF protein and activity, respectively; their platelets had neither hyper-aggregation nor endogenous thrombin generation (ETP). Rosuvastatin, but not atorvastatin, normalized platelet cholesterol, TF protein and FXa generation. It also increased slightly the plasma HDL-C levels, which correlated negatively with TF-PCA.

CONCLUSIONS

Platelets from HC-patients were not hyper-responsive to low concentrations of classical agonists and had normal PRP-ETP, before and after statin administration. However, washed platelets from HC-patients had increased membrane cholesterol, TF protein and TF-PCA. The platelet TF-dependent PCA was specifically expressed after VWF-induced GPIbα activation. Rosuvastatin, but not atorvastatin treatment, normalized the membrane cholesterol, TF protein and TF-PCA in HC-patients, possibly unveiling a new pleiotropic effect of rosuvastatin. Modulation of platelet TF-PCA may become a novel target to prevent/treat atherothrombosis without increasing bleeding risks.

Efficacy of Clopidogrel and Clinical Outcome When Clopidogrel Is Coadministered With Atorvastatin and Lansoprazole: A Prospective, Randomized, Controlled Trial

This prospective, randomized, nonblind, controlled trial evaluated the effects of clopidogrel on platelet function upon coadministration with atorvastatin and lansoprazole. One hundred four adult patients with non-ST-segment elevated acute coronary syndrome (NSTE-ACS) who underwent percutaneous coronary intervention (PCI) with drug-eluting stent implantation were included. All patients were treated with standard dual antiplatelet therapy (DAPT) plus rosuvastatin 10  mg daily after the operation. On the sixth day after PCI, patients were randomly divided into 4 groups, Group A: DAPT + atorvastatin 20  mg daily (a change from rosuvastatin to atorvastatin) + lansoprazole 30  mg daily, Group B: DAPT + atorvastatin 20  mg daily (a change from rosuvastatin to atorvastatin), Group C: DAPT + lansoprazole 30  mg daily (continuing to take rosuvastatin), Group D is the control group. Additional drugs were used according to the situation of patients. Platelet function and concentrations of platelet activation markers (granular membrane protein 140 (P-selectin), thromboxane B2 (TXB2), and human soluble cluster of differentiation 40 ligand (sCD40L)) were assessed before randomization and at 15- and 30-day follow-up visits. All patients were maintained on treatment for 6 months and observed for bleeding and ischemic events. A total of 104 patients were enrolled, 27 patients in group A, 26 patients in Group B/C, 25 patients in Group D separately, and all the patients were analyzed. There were no differences in platelet function and the levels of platelet activation markers (P-selectin, TXB2, and sCD40L) among or within the 4 groups at the 3 time points of interest (P > 0.05). In the subsequent 6 months, no significant bleeding events occurred, and 12 patients experienced ischemic events, these results were also not significantly different among the groups (P > 0.05). In patients diagnosed with NSTE-ACS who have had drug-eluting stent implantation, simultaneously administering clopidogrel, atorvastatin, and lansoprazole did not decrease the antiplatelet efficacy of clopidogrel or increase adverse event frequency over 6 months.

Clinical pharmacokinetics and pharmacodynamics of clopidogrel

Acute coronary syndromes (ACS) remain life-threatening disorders, which are associated with high morbidity and mortality. Dual antiplatelet therapy with aspirin and clopidogrel has been shown to reduce cardiovascular events in patients with ACS. However, there is substantial inter-individual variability in the response to clopidogrel treatment, in addition to prolonged recovery of platelet reactivity as a result of irreversible binding to P2Y12 receptors. This high inter-individual variability in treatment response has primarily been associated with genetic polymorphisms in the genes encoding for cytochrome (CYP) 2C19, which affect the pharmacokinetics of clopidogrel. While the US Food and Drug Administration has issued a boxed warning for CYP2C19 poor metabolizers because of potentially reduced efficacy in these patients, results from multivariate analyses suggest that additional factors, including age, sex, obesity, concurrent diseases and drug-drug interactions, may all contribute to the overall between-subject variability in treatment response. However, the extent to which each of these factors contributes to the overall variability, and how they are interrelated, is currently unclear. The objective of this review article is to provide a comprehensive update on the different factors that influence the pharmacokinetics and pharmacodynamics of clopidogrel and how they mechanistically contribute to inter-individual differences in the response to clopidogrel treatment.

Concomitant use of clopidogrel and statins and risk of major adverse cardiovascular events following coronary stent implantation

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• The CYP3A4 inhibition by lipophilic statins may attenuate the effectiveness of clopidogrel. • No studies have measured drug exposure in a time-varying manner that detects discontinuation and restart of clopidogrel and statin therapy, allowing clinical quantification of the interaction effect.

WHAT THIS STUDY ADDS

• Clopidogrel and CYP3A4-metabolizing statin use were each associated with a substantially reduced rate of major adverse cardiovascular events within 12 months after coronary stent implantation. • Although we observed an interaction between use of clopidogrel and statins, statin use vs. non-use was not associated with an increased rate of major adverse cardiovascular events in patients using clopidogrel after coronary stent implantation.

AIMS

To examine whether CYP3A4-metabolizing statin use modified the association between clopidogrel use and major adverse cardiovascular events (MACE) after coronary stent implantation, using time-varying drug exposure ascertainment.

METHODS

We conducted this population-based cohort study in Western Denmark (population: 3 million) using medical databases. We identified all 13 001 patients with coronary stent implantation between 2002 and 2005 and their comorbidities. During 12 months of follow-up, we tracked the use of clopidogrel and CYP3A4-metabolizing statins and the rate of MACE. We used Cox regression to compute hazard ratios (HRs) controlling for potential confounders.

RESULTS

The rate of MACE per 1000 person years was 104 for concomitant clopidogrel and statin use, 130 for clopidogrel without statin use, 108 for statin without clopidogrel use and 446 for no use of either drug. The adjusted HR comparing clopidogrel use with non-use was 0.68 (95% confidence interval (CI) 0.58, 0.79) among statin users and 0.34 (95% CI 0.29, 0.40) among statin non-users, yielding an interaction effect (i.e. relative rate increase) of 1.97 (95% CI 1.59, 2.44). The adjusted HR for MACE comparing statin use with non-use was 0.97 (95% CI 0.83, 1.13) among clopidogrel users and 0.49 (95% CI 0.42, 0.57) among clopidogrel non-users.

CONCLUSIONS

Clopidogrel and CYP3A4-metabolizing statin use were each associated with a substantially reduced rate of MACE within 12 months after coronary stent implantation. Although we observed an interaction between use of clopidogrel and statins, statin use vs. non-use was not associated with an increased rate of MACE in patients using clopidogrel after coronary stent implantation.

Clopidogrel-drug interactions

Multidrug therapy increases the risk for drug-drug interactions. Clopidogrel, a prodrug, requires hepatic cytochrome P450 (CYP) metabolic activation to produce the active metabolite that inhibits the platelet P2Y₁₂ adenosine diphosphate (ADP) receptor, decreasing platelet activation and aggregation processes. Atorvastatin, omeprazole, and several other drugs have been shown in pharmacodynamic studies to competitively inhibit CYP activation of clopidogrel, reducing clopidogrel responsiveness. Conversely, other agents increase clopidogrel responsiveness by inducing CYP activity. The clinical implications of these pharmacodynamic interactions have raised concern because many of these drugs are coadministered to patients with coronary artery disease. There are multiple challenges in proving that a pharmacodynamic drug-drug interaction is clinically significant. To date, there is no consistent evidence that clopidogrel-drug interactions impact adverse cardiovascular events. Statins and proton pump inhibitors have been shown to decrease adverse clinical event rates and should not be withheld from patients with appropriate indications for therapy because of concern about potential clopidogrel-drug interactions. Clinicians concerned about clopidogrel-drug interactions have the option of prescribing either an alternative platelet P2Y₁₂ receptor inhibitor without known drug interactions, or statin and gastro-protective agents that do not interfere with clopidogrel metabolism.

Antiplatelet drug interactions

Both laboratory studies in healthy volunteers and clinical studies have suggested adverse interactions between antiplatelet drugs and other commonly used medications. Interactions described include those between aspirin and ibuprofen, aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), and the thienopyridine, clopidogrel, and drugs inhibiting CYP2C19, notably the proton pump inhibitors (PPI) omeprazole and esomeprazole. Other interactions between thienopyridines and CYP3A4/5 have also been reported for statins and calcium channel blockers. The ibuprofen/aspirin interaction is thought to be caused by ibuprofen blocking the access of aspirin to platelet cyclo-oxygenase. The thienopyridine interactions are caused by inhibition of microsomal enzymes that metabolize these pro-drugs to their active metabolites. We review the evidence for these interactions, assess their clinical importance and suggest strategies of how to deal with them in clinical practice. We conclude that ibuprofen is likely to interact with aspirin and reduce its anti-platelet action particularly in those patients who take ibuprofen chronically. This interaction is of greater relevance to those patients at high cardiovascular risk. A sensible strategy is to advise users of aspirin to avoid chronic ibuprofen or to ingest aspirin at least 2 h prior to ibuprofen. Clearly the use of NSAIDs that do not interact in this way is preferred. For the clopidogrel CYP2C19 and CYP3A4/5 interactions, there is good evidence that these interactions occur. However, there is less good evidence to support the clinical importance of these interactions. Again, a reasonable strategy is to avoid the chronic use of drugs that inhibit CYP2C19, notably PPIs, in subjects taking clopidogrel and use high dose H2 antagonists instead. Finally, anti-platelet agents probably interact with other drugs that affect platelet function such as selective serotonin reuptake inhibitors, and clinicians should probably judge patients taking such combination therapies as at high risk for bleeding.