Investigation of drug-drug interactions between clopidogrel and fluoxetine

High prevalence of potential psychotropic drugs interactions among Brazilian dental patients

OBJECTIVE

To determine the prevalence of potential drug-drug interactions involving psychotropics prescribed by dentists, and dispensed by the public healthcare system, as well as to describe the severity and level of evidence of those interactions in the state of Minas Gerais, Brazil.

MATERIALS AND METHODS

We conducted data analysis from pharmaceutical claims in which dental patients received systemic psychotropics in 2017. Data from the Pharmaceutical Management System provided the drug dispensing history of the patients, allowing the identification of those on concomitant medication use. The outcome was the occurrence of potential drug-drug interactions, which were detected according to IBM Micromedex®. Independent variables were the patient's sex, age, and the number of drugs used. Descriptive statistics was performed using SPSS v. 26.

RESULTS

Overall, 1480 individuals were prescribed psychotropic drugs. The prevalence of potential drug-drug interactions was 24.8% (n = 366). The total of 648 interactions was observed and, most of which were of major severity (n = 438, 67.6%). Most interactions occurred in female individuals (n = 235; 64.2%), with 46.0 (±17.3) years-old, concurrently taking 3.7 (±1.9) drugs.

CONCLUSION

A substantial proportion of dental patients presented potential drug-drug interactions, mostly of major severity, which might be life-threatening.

Effect of chronic unpredicted mild stress-induced depression on clopidogrel pharmacokinetics in rats

Background

Clopidogrel is widely used to prevent and treat cardiovascular atherosclerosis and thrombosis. However, disturbance in the expression and activity of liver cytochrome metabolic enzymes significantly changes clopidogrel efficacy. Therefore, the effect of chronic unpredictable mild stress (CUMS)-induced depression on the expression of liver cytochrome metabolic enzymes and clopidogrel pharmacokinetics in rats were explored.

Methods

Nine different CUMSs were selected to establish a rat model of depression. Open field experiment and sucrose preference test were applied to explore the depressive behaviors. The concentration of serotonin in the cortex of depressed rats was determined using enzyme linked immunosorbent assay (ELISA). All rats were given 10 mg/kg clopidogrel orally after 12 weeks, and blood samples were collected at different time points. The clopidogrel concentration and CYP2C19/ CYP2C9 activity in rat liver microsomes were assayed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The rat liver drug enzymes expression was determined by Real-Time Quantitative Reverse Transcription PCR (RT-qPCR).

Results

Open field experiment and sucrose preference test indicated the successful construction of the CUMS-induced depression model. The concentration of serotonin in the cortex of depressed rats decreased by 42.56% (^∗∗ p < 0.01). The area under the curve of clopidogrel pharmacokinetics decreased by 33.13% (^∗ p < 0.05) in the depression rats, while distribution volume and clearance increased significantly (^∗∗ p < 0.01). The half-time and distribution volume did not significantly differ. The CYP2C19 and CYP2C9 activity of liver microsomes in the CUMS-induced depression group were significantly higher than that in the control group (^∗∗ p < 0.01). CYP2C11 and CYP1A2 mRNA expression up-regulated approximately 1.3 - fold in the depressed rat livers compared with that in the control, whereas that of CYP2C13 was down-regulated by 27.43% (^∗∗ p < 0.01). CYP3A1 and CYP2C12 expression were slightly up-regulated, and that of CES1 did not change.

Conclusions

These results indicated that CUMS-induced depression altered clopidogrel pharmacokinetics, and the change in CYP450 activity and expression in depressed rat livers might contribute to the disturbance of clopidogrel pharmacokinetics.

Physiologically Based Pharmacokinetic (PBPK) Modeling of Clopidogrel and Its Four Relevant Metabolites for CYP2B6, CYP2C8, CYP2C19, and CYP3A4 Drug–Drug–Gene Interaction Predictions

The antiplatelet agent clopidogrel is listed by the FDA as a strong clinical index inhibitor of cytochrome P450 (CYP) 2C8 and weak clinical inhibitor of CYP2B6. Moreover, clopidogrel is a substrate of—among others—CYP2C19 and CYP3A4. This work presents the development of a whole-body physiologically based pharmacokinetic (PBPK) model of clopidogrel including the relevant metabolites, clopidogrel carboxylic acid, clopidogrel acyl glucuronide, 2-oxo-clopidogrel, and the active thiol metabolite, with subsequent application for drug–gene interaction (DGI) and drug–drug interaction (DDI) predictions. Model building was performed in PK-Sim^® using 66 plasma concentration-time profiles of clopidogrel and its metabolites. The comprehensive parent-metabolite model covers biotransformation via carboxylesterase (CES) 1, CES2, CYP2C19, CYP3A4, and uridine 5′-diphospho-glucuronosyltransferase 2B7. Moreover, CYP2C19 was incorporated for normal, intermediate, and poor metabolizer phenotypes. Good predictive performance of the model was demonstrated for the DGI involving CYP2C19, with 17/19 predicted DGI AUC_last and 19/19 predicted DGI C_max ratios within 2-fold of their observed values. Furthermore, DDIs involving bupropion, omeprazole, montelukast, pioglitazone, repaglinide, and rifampicin showed 13/13 predicted DDI AUC_last and 13/13 predicted DDI C_max ratios within 2-fold of their observed ratios. After publication, the model will be made publicly accessible in the Open Systems Pharmacology repository.

Assessing the Mechanism of Fluoxetine-Mediated CYP2D6 Inhibition

Fluoxetine is still one of the most widely used antidepressants in the world. The drug is extensively metabolized by several cytochrome P450 (CYP450) enzymes and subjected to a myriad of CYP450-mediated drug interactions. In a multidrug regimen, preemptive mitigation of drug-drug interactions requires knowledge of fluoxetine actions on these CYP450 enzymes. The major metabolic pathway of fluoxetine leading to the formation of its active metabolite, norfluoxetine, is mediated by CYP2D6. Fluoxetine and norfluoxetine are strong affinity substrates of CYP2D6 and can inhibit, potentially through various mechanisms, the metabolism of other sensitive CYP2D6 substrates. Remarkably, fluoxetine-mediated CYP2D6 inhibition subsides long after fluoxetine first passes through the liver and even remains long after the discontinuation of the drug. Herein, we review pharmacokinetic and pharmacogenetic information to help us understand the mechanisms underlying the prolonged inhibition of CYP2D6 following fluoxetine administration. We propose that long-term inhibition of CYP2D6 is likely a result of competitive inhibition. This is due to strong affinity binding of fluoxetine and norfluoxetine to the enzyme and unbound fluoxetine and norfluoxetine levels circulating in the blood for a long period of time because of their long elimination half-life. Additionally, we describe that fluoxetine is a CYP2C9 substrate and a mechanism-based inhibitor of CYP2C19.

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.

Concomitant use of drugs known to cause interactions with oral antiplatelets-polypharmacy in acute coronary syndrome outpatients in Finland

PURPOSE

Use of oral antiplatelets (OAPs) is essential for preventing thrombotic events in patients with acute coronary syndrome (ACS). Effects of clopidogrel, prasugrel, and ticagrelor may be enhanced due to pharmacodynamic interactions, but as CYP substrates, they are prone to pharmacokinetic interactions too. The aim was to study polypharmacy in ACS patients following hospital discharge.

METHODS

This observational drug utilization study linked patient-level data from nationwide registers. The study population consisted of adult ACS patients discharged from Finnish hospitals in 2009-2013. Logistic regression was used to model the probability of drug-drug interactions with odd ratios for predefined predictors such as age, gender, and ACS type.

RESULTS

In the cohort of 54,416 ACS patients, 91% of those treated with OAP received clopidogrel. Of clopidogrel-treated patients, 12% purchased warfarin at least once while on clopidogrel treatment. Old age, male sex, ST-elevation myocardial infarction as index event, and a history of previous ACS events were associated with an increased risk of warfarin-OAP interaction (p < 0.001 for all). Ibuprofen, and serotonergic drugs tramadol, citalopram, and escitalopram were the next most common drugs causing pharmacodynamic interactions. In general, concomitant use of drugs known to cause pharmacokinetic interactions was rare, but both esomeprazole and omeprazole were prescribed in more than 6% of clopidogrel-treated patients.

CONCLUSIONS

Warfarin and ibuprofen were the most commonly used concomitant medications causing pharmacodynamic interactions and potentially increasing the risk of bleeding in OAP-treated patients. Esomeprazole and omeprazole were used in clopidogrel-treated patients although there are alternatives available for gastric protection.

Choosing among second-generation antidepressant treatments for depressed patients with cardiac diseases

Objectives: The present paper aimed to assist physicians in the accurate choice among second-generation agents (SGAs) for patients with cardiovascular disease (CVD). Methods: We reviewed the published pharmacokinetic (PK) and pharmacodynamic (PD) clinical data that report potential -or absence of- drug interactions between second-generation agents (SGAs) and CVD drugs most commonly used in cardiology, including antiplatelet drugs and anticoagulants, statins, beta-blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, diuretics and the antiarrhythmic drugs amiodarone and digoxin. We also reviewed the cardiovascular safety profile that has been published for each class of SGAs and side effects reported by patients with CVD. Results: Most relevant PK/PD data about SGAs and CVD drugs are based on small studies or detailed case reports. In many cases, the drug interactions are at most assessed in healthy volunteers so that the clinical relevance of findings needs further investigation in patients with CVD. Case reports of serious, sometimes fatal reactions due to concomitant administration of certain drugs require careful consideration. The major cardiac side effects of SGAs include HR increase, postural hypotension and slight prolongation of the intraventricular conduction time and QT interval. On normal dosage of antidepressants, both advanced heart block and ventricular arrhythmias could occur in patients with severe heart disease, together with clinically important loss of myocardial contractile force. Conclusions: Data reported in the present review should help physicians about their decision-making processes that govern SGAs use in CVD patients.

Efficacy and mechanism of acupuncture for ischemic poststroke depression: Study protocol for a multicenter single-blinded randomized sham-controlled trial

INTRODUCTION

Poststroke depression is a serious and common complication of stroke, especially the ischemic poststroke depression. Antidepressants are used in poststroke depression, and acupuncture may be an alternative approach. However, the efficacy and mechanism of acupuncture for poststroke depression has not been confirmed.

METHODS/DESIGN

This is a multicenter, central-randomized, single-blind, sham-controlled clinical trial. We will allocate 208 subjects aged between 40 and 80 years old, diagnosed with initial poststroke depression (PSD) within 6 months to 2 groups randomly in a ratio of 1:1. Patients in the experimental group will be treated with traditional acupuncture and placebo pills, whereas the others in the control group will be treated with sham-acupoints acupuncture and antidepressant (fluoxetine hydrochloride tablets). All will be given acupuncture and/or medication treatment for 12 weeks, and then received 12-week follow-up. Patients will be evaluated with the 17-item Hamilton Depression Scale and Se1f-rating Depression Scale for depression state, National Institute of Health Stroke Scale for neurological deficit, Modified Barthel Index for activities of daily living, Treatment Emergent Symptom Scale for side effects of treatments, diagnosis and evaluation criteria of traditional Chinese medicine for stroke (try out) for curative effects of stroke, and clinical global impression for synthesize effect before and the 2nd, 4th, 8th, and 12th week of treatment, 24th week of follow-up. Study on mechanisms of acupuncture will be revealed through the diversity of brain metabolites (choline-containing compounds [Cho], N-acetylaspartate [NAA], myoinositol, glutamine and glutamate complex, creatine [Cr], Cho/Cr, Cho/NAA, Cr/NAA) in bilateral dorsolateral prefrontal cortex and anterior cingulate cortex monitored by proton magnetic resonance spectroscopy, and serum monoamine neurotransmitters (5-hydroxytryptamine, norepinephrine, dopamine) and cytokines (brain-derived neurotrophic factor [BDNF], interleukin [IL]-4, IL-6, IL-10, IL-18, IL-1β, tumor necrosis factor alpha) before and the 12th week of treatment. Baseline characteristics of patients will be summarized by groups and compared with chi-square for categorical variables, and 2-sample t tests or Wilcoxon rank-sum test for the continuous variables. Primary and secondary outcomes according to the measurement times are applicable to univariate repetitive measurement deviation analysis or 2-sample t tests, or Wilcoxon rank-sum test.

CONCLUSION

The present research is designed to investigate efficacy and mechanism of traditional acupuncture therapy on ischemic PSD, also to explore the correlation between cerebra metabolic and serologic factors, and ischemic PSD. With this research, we are looking forward to find out an appropriate alternative nondrug therapy for PSD people to alleviate the adverse effects and drug dependence caused by antidepressants.

Updating the Evidence of the Interaction Between Clopidogrel and CYP2C19-Inhibiting Selective Serotonin Reuptake Inhibitors: A Cohort Study and Meta-Analysis

INTRODUCTION

We previously found that patients who initiate clopidogrel while treated with a cytochrome P450 (CYP) 2C19-inhibiting selective serotonin reuptake inhibitor (SSRI) have a higher risk of subsequent ischemic events than patients treated with other SSRIs. It is not known whether initiating an inhibiting SSRI while treated with clopidogrel will also increase risk of ischemic events.

OBJECTIVE

The aim of this study was to assess clinical outcomes following initiation of a CYP2C19-inhibiting SSRI versus initiation of other SSRIs among patients treated with clopidogrel and to update existing evidence on the clinical impact of clopidogrel-SSRI interaction.

METHODS

Using five US databases (1998-2013), we conducted a cohort study of clopidogrel initiators who encountered treatment with SSRI during their clopidogrel therapy. Patients were matched by propensity score (PS) and followed for as long as they were exposed to both clopidogrel and index SSRI group. Outcomes were a composite ischemic event (myocardial infarction, ischemic stroke, or a revascularization procedure, whichever came first) and a composite major bleeding event (gastrointestinal bleed or hemorrhagic stroke, whichever came first). Results were combined via random-effects meta-analysis with previous evidence from subjects initiating clopidogrel while on SSRI therapy.

RESULTS

The PS-matched cohort comprised 2346 clopidogrel users starting CYP2C19-inhibiting SSRI therapy and 16,115 starting other SSRIs (mean age 61 years; 59% female). Compared with those treated with a non-inhibiting SSRI, the hazard ratio (HR) for patients treated with a CYP2C19-inhibiting SSRI was 1.07 (95% confidence interval [CI] 0.82-1.40) for the ischemic outcome and 1.00 (95% CI 0.42-2.36) for bleeding. The pooled estimates were 1.11 (95% CI 1.01-1.22) for ischemic events and 0.80 (95% CI 0.55-1.18) for bleeding.

CONCLUSIONS

We observed similar estimates of association between the two studies. The updated evidence still indicates a small decrease in clopidogrel effectiveness associated with concomitant exposure to clopidogrel and CYP2C19-inhibiting SSRIs.

The Present and Future of Precision Medicine in Psychiatry: Focus on Clinical Psychopharmacology of Antidepressants

Precision medicine is a concept which is recently gaining momentum in all branches of medicine. In particular in psychiatry it is greatly needed given the huge societal costs of psychiatric disorders and given the long time needed to observe benefit from treatments and the response variability. The future will be based on biological determinants, however until such an interesting but still futuristic aim will be reached, at present we may only rely on clinical features to guide our individualized prescription which is currently still frequently based on personal opinion and subjective previous experiences. The aim of this review is to offer an overview of the main aspects to take into consideration when prescribing an antidepressant treatment to reach the best precision medicine using clinical information. More than 40 compounds are available for treating depression and a similar amount of compounds for other psychiatric disorders. The process of matching the profile of the patient with all different profiles of available compounds is therefore quite complex. Our everyday prescribing procedure should take into consideration a number of factors such as the knowledge of the profile of available compounds versus the symptomatology profile of the subject, previous efficacy, medical comorbidities, tolerability profile, individual preferences, and family history. While we are waiting more complex algorithms including biological or genetic measures, it is possible to optimize our current prescription practice by using all available information in order to obtain as much as possible an evidence based precision medicine prescription.

Impact of an Interaction Between Clopidogrel and Selective Serotonin Reuptake Inhibitors

Clopidogrel is a pro-drug that requires activation by the cytochrome P450 (CYP) enzyme system. Patients receiving clopidogrel are often treated with selective serotonin reuptake inhibitors (SSRIs) for co-existing depression. SSRIs that inhibit the CYP2C19 enzyme have the potential to reduce the effectiveness of clopidogrel. Using 5 US databases (1998 to 2013), we conducted a cohort study of adults who initiated clopidogrel while being treated with either an SSRI that inhibits CYP2C19 (fluoxetine and fluvoxamine) or a noninhibiting SSRI. Patients were matched by propensity score and followed for as long as they were exposed to both clopidogrel and the index SSRI group (primary analysis) or for 180 days after clopidogrel initiation (sensitivity analysis). Outcomes included a composite ischemic event (myocardial infarction, ischemic stroke, or a revascularization procedure) and a composite major bleeding event (gastrointestinal bleed or hemorrhagic stroke). The final propensity score-matched cohort comprised 9,281 clopidogrel initiators on CYP2C19-inhibiting SSRIs and 44,278 clopidogrel initiators on a noninhibiting SSRIs. Compared with those treated with a noninhibiting SSRI, patients on a CYP2C19-inhibiting SSRI had an increased risk of ischemic events (hazard ratio [HR] 1.12; 95% confidence interval [CI] 1.01 to 1.24), which was more pronounced in patients ≥65 years (HR 1.22; 95% CI 1.00 to 1.48). The HR for major bleeding was 0.76 (95% CI 0.50 to 1.17). In conclusion, the findings from this large, population-based study suggest that being treated with a CYP2C19-inhibiting SSRI when initiating clopidogrel may be associated with slight decrease in effectiveness of clopidogrel.

Effect of antituberculosis treatment on CYP2C19 enzyme activity in genetically polymorphic South Indian Tamilian population

Patients on antituberculosis therapy (ATT) are more prone to drug interactions in the presence of coexisting illnesses which require drug therapy. Rifampicin is a pleiotropic inducer of CYP enzymes, and isoniazid is an enzyme inhibitor. Genetic variations are common in the gene coding for CYP2C19 enzyme. These variations would be important in predicting the individual variations in CYP2C19 activity. The objectives of the study were to find the net effect of 1-month ATT on CYP2C19 enzyme activity and its association with CYP2C19 genetic polymorphisms. Newly diagnosed tuberculosis patients (n = 125) were included in the study. Before commencing ATT, they were given a single dose of omeprazole 20 mg as a probe drug for CYP2C19. Blood sample was collected after 3 h to carry out phenotyping for CYP2C19 enzyme by measuring omeprazole hydroxylation index (OHI) using LC-MS/MS. The phenotyping procedure was repeated after 1 month of ATT. CYP2C19 genotyping was carried out by PCR-RFLP method. Significant reduction in OHI was observed after 1 month of ATT in all the metabolizer groups. The percentage reduction in OHI was maximum with poor metabolizers, 84.1 (IQR - 74.6, 86.6), and minimum with ultra-rapid metabolizers, 39.6 (IQR - 12.7, 54.7). CYP2C19 enzyme induction is predominant in patients after 1 month of antituberculosis treatment (ATT). Genetic variations in the enzyme could not clearly explain the interindividual differences in induction. There is a potential risk of drug failure/adverse effect in poor metabolizers regardless of their genotype after ATT.

Severe potential drug-drug interactions in older adults with dementia and associated factors

OBJECTIVE

To identify the main severe potential drug-drug interactions in older adults with dementia and to examine the factors associated with these interactions.

METHOD

This was a cross-sectional study. The enrolled patients were selected from six geriatrics clinics of tertiary care hospitals across Mexico City. The patients had received a clinical diagnosis of dementia based on the current standards and were further divided into the following two groups: those with severe drug-drug interactions (contraindicated/severe) (n=64) and those with non-severe drug-drug interactions (moderate/minor/absent) (n=117). Additional socio-demographic, clinical and caregiver data were included. Potential drug-drug interactions were identified using Micromedex Drug Reax 2.0® database.

RESULTS

A total of 181 patients were enrolled, including 57 men (31.5%) and 124 women (68.5%) with a mean age of 80.11±8.28 years. One hundred and seven (59.1%) patients in our population had potential drug-drug interactions, of which 64 (59.81%) were severe/contraindicated. The main severe potential drug-drug interactions were caused by the combinations citalopram/anti-platelet (11.6%), clopidogrel/omeprazole (6.1%), and clopidogrel/aspirin (5.5%). Depression, the use of a higher number of medications, dementia severity and caregiver burden were the most significant factors associated with severe potential drug-drug interactions.

CONCLUSIONS

Older people with dementia experience many severe potential drug-drug interactions. Anti-depressants, antiplatelets, anti-psychotics and omeprazole were the drugs most commonly involved in these interactions. Despite their frequent use, anti-dementia drugs were not involved in severe potential drug-drug interactions. The number and type of medications taken, dementia severity and depression in patients in addition to caregiver burden should be considered to avoid possible drug interactions in this population.

Differential impact of selective serotonin reuptake inhibitors on platelet response to clopidogrel: a randomized, double-blind, crossover trial

STUDY OBJECTIVE

To assess the effect of two selective serotonin reuptake inhibitors (SSRIs), fluvoxamine and citalopram, that markedly differ in their level of cytochrome P450 (CYP) 2C19 inhibition, on the laboratory response to clopidogrel, a prodrug requiring metabolism by the CYP system, and especially CYP2C19, to produce its active form.

DESIGN

Randomized, double-blind, crossover trial.

SETTING

Clinical research unit of an academic medical center.

SUBJECTS

Fifteen healthy male volunteers.

INTERVENTION

All subjects received clopidogrel as a 300-mg loading dose on day 1, followed by 75 mg/day on days 2 and 3. Platelet function was tested at baseline and then after clopidogrel treatment on day 3. After a washout period of 2 weeks, subjects were randomly assigned in a double-blind manner to receive either citalopram 20 mg/day or fluvoxamine 100 mg/day for 7 days. On day 5, platelet function was tested while receiving the SSRI treatment alone; then, a 300-mg clopidogrel loading dose was administered, followed by clopidogrel 75 mg/day on days 6 and 7. Platelet function was then reassessed on day 7 while receiving the combination of the SSRI and clopidogrel. The treatment protocol was then repeated after a washout period of 2 weeks in all subjects with the other SSRI.

MEASUREMENTS AND MAIN RESULTS

The antiplatelet effects of fluvoxamine and citalopram and their interactions with clopidogrel were assessed. The response to these three drugs was assessed by light transmittance aggregometry and vasodilator-stimulated phosphoprotein phosphorylation, reporting P2Y12 receptor reactivity. Both fluvoxamine and citalopram tended to reduce adenosine diphosphate-induced aggregation: 80.8 ± 3.4% at baseline, 67.3 ± 6.3% while receiving citalopram, and 65.8 ± 6.4% while receiving fluvoxamine. All subjects had a good laboratory response to clopidogrel, with a mean aggregation of 23.5 ± 3.2% and a mean platelet reactivity index of 47.7 ± 3.9% (p<0.001 compared with baseline for both methods). Laboratory response to clopidogrel was significantly attenuated in the presence of fluvoxamine compared with the response in the presence of citalopram as tested both by aggregometry (32.3 ± 4.2% vs 23.4 ± 3%, p=0.04) and by vasodilator-stimulated phosphoprotein phosphorylation (52.7 ± 5.1% vs 35.9 ± 4.2%, p=0.02).

CONCLUSION

Fluvoxamine attenuated the laboratory response to clopidogrel, possibly through inhibition of CYP2C19, whereas citalopram did not affect this response. These potential drug interactions should be taken into consideration in the selection of the appropriate antidepressant agent for patients who are treated with clopidogrel.

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.

Pharmacokinetic drug interactions with clopidogrel: updated review and risk management in combination therapy

Background

Coprescribing of clopidogrel and other drugs is common. Available reviews have addressed the drug–drug interactions (DDIs) when clopidogrel is as an object drug, or focused on combination use of clopidogrel and a special class of drugs. Clinicians may still be ignorant of those DDIs when clopidogrel is a precipitant drug, the factors determining the degree of DDIs, and corresponding risk management.

Methods

A literature search was performed using PubMed, MEDLINE, Web of Science, and the Cochrane Library to analyze the pharmacokinetic DDIs of clopidogrel and new P2Y₁₂ receptor inhibitors.

Results

Clopidogrel affects the pharmacokinetics of cerivastatin, repaglinide, ferulic acid, sibutramine, efavirenz, and omeprazole. Low efficacy of clopidogrel is anticipated in the presence of omeprazole, esomeprazole, morphine, grapefruit juice, scutellarin, fluoxetine, azole antifungals, calcium channel blockers, sulfonylureas, and ritonavir. Augmented antiplatelet effects are anticipated when clopidogrel is coprescribed with aspirin, curcumin, cyclosporin, St John’s wort, rifampicin, and angiotensin-converting enzyme inhibitors. The factors determining the degree of DDIs with clopidogrel include genetic status (eg, cytochrome P540 [CYP]2B6*6, CYP2C19 polymorphism, CYP3A5*3, CYP3A4*1G, and CYP1A2-163C.A), species differences, and dose strength. The DDI risk does not exhibit a class effect, eg, the effects of clopidogrel on cerivastatin versus other statins, the effects of proton pump inhibitors on clopidogrel (omeprazole, esomeprazole versus pantoprazole, rabeprazole), the effects of rifampicin on clopidogrel versus ticagrelor and prasugrel, and the effects of calcium channel blockers on clopidogrel (amlodipine versus P-glycoprotein-inhibiting calcium channel blockers). The mechanism of the DDIs with clopidogrel involves modulating CYP enzymes (eg, CYP2B6, CYP2C8, CYP2C19, and CYP3A4), paraoxonase-1, hepatic carboxylesterase 1, P-glycoprotein, and organic anion transporter family member 1B1.

Conclusion

Effective and safe clopidogrel combination therapy can be achieved by increasing the awareness of potential changes in efficacy and toxicity, rationally selecting alternatives, tailoring drug therapy based on genotype, checking the appropriateness of physician orders, and performing therapeutic monitoring.