Effects of PPIs and an H2 blocker on the antiplatelet function of clopidogrel in Japanese patients under dual antiplatelet therapy

An update on oral antiplatelet drug interactions with proton pump inhibitors: what are the risks?

INTRODUCTION

Aspirin and anti-P2Y12 are widely prescribed in cardiovascular patients, often in combination with proton pump inhibitors (PPIs) to limit the risk of upper gastrointestinal bleedings. The potential interaction between PPIs and antiplatelet agents has been widely discussed, but doubts remain as to whether PPIs may reduce the cardiovascular protection provided by aspirin, prasugrel, ticagrelor, and clopidogrel.

AREAS COVERED

Many pharmacokinetic (PK) and pharmacodynamic (PD) studies have confirmed the interaction, especially between PPIs and clopidogrel, but with uncertain consequences on clinical outcomes. Therefore, we aimed to summarize the evidence for the widespread combined use of oral antiplatelet drugs and PPIs, to outline the current evidence supporting or opposing drug-drug interaction, and to discuss the clinical implications of such interactions.

EXPERT OPINION

A large body of evidence describes the PK/PD interaction of antiplatelet drugs with PPIs and its potential role in increasing clinical cardiovascular adverse events, but no solid clinical data have confirmed these effects. In the light of the published studies, there seems to be no restriction on the choice of PPI with aspirin, prasugrel, and/or ticagrelor. The choice of a PPI with no (or minimal) interference with the hepatic cytochrome P450 2C19 is preferred in patients receiving clopidogrel.

Antacid Therapy in Coronary Artery Disease and Heart Failure: Proton Pump Inhibitors vs. H2 Receptor Blockers

PURPOSE

Acid suppressive therapy using histamine H2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) can be utilized for the prevention of gastrointestinal bleeding (GIB) among patients with cardiovascular disease receiving dual antiplatelet therapy (DAPT). However, emerging data suggests underlying associations between PPI or H2RA use and cardiovascular disease incidence, progression, and mortality. This review explores the history of acid suppressive therapies and their use in cardiovascular disease patients and the growing evidence in support of H2RA use.

RECENT FINDINGS

PPIs were originally championed as better than H2RAs for preventing GIB events in cardiovascular disease patients on DAPT therapy, but there is evidence to suggest that drug-drug interactions between clopidogrel and PPIs may translate to worse cardiovascular outcomes. Studies demonstrating PPI superiority in the setting of DAPT were also limited due to small sample sizes and high levels of bias. Consequently, there is renewed interest in H2RAs for patients on DAPT with some data demonstrating similar or improved clinical outcomes over PPI therapy. Additionally, studies have discovered a possible role for H2RAs in the management of heart failure (HF) incidence, symptoms, and mortality. Studies comparing H2RAs and PPIs in patients on DAPT have demonstrated mixed results for cardiovascular and GIB outcomes, with several studies being underpowered and limited by biases. Recent clinical and pre-clinical studies now support the noninferiority of H2RAs for major outcomes and even utility in HF. These findings suggest that H2RAs may warrant reconsideration as an acid suppressive therapy over PPIs for patients on DAPT or with HF.

Effects of treatment with clopidogrel with or without proton pump inhibitor omeprazole on the risk of ischemic stroke: a nationwide cohort study

Most proton pump inhibitors (PPIs) inhibit the bioactivation of clopidogrel to its active metabolite. There is controversy concerning whether PPIs alter the effectiveness of clopidogrel in reducing the risk of ischemic stroke (IS). We therefore aimed to examine the risk of IS associated with concomitant use of clopidogrel and omeprazole, a PPI commonly used in clinical settings. We conducted a retrospective cohort study using the National Health Insurance Research Database of Taiwan dated from 2000 to 2013. The study cohorts comprised 407 patients diagnosed with acute coronary syndrome (ACS) and with concomitant use of clopidogrel and omeprazole (the exposed cohort), 814 ACS patients with single use of clopidogrel (the comparison cohort), and 230 ACS patients with concurrent use of clopidogrel and pantoprazole (the reference cohort). The primary outcome was incident IS. The hazard ratios (HRs) and 95% confidence intervals (CIs) derived from the time-dependent Cox regression model were used to assess the association between concomitant use of clopidogrel and omeprazole and the risk of IS. The incidence rate of IS was significantly higher in the exposed cohort (81.67 per 1000 person-years) than in the comparison cohort (57.45 per 1000 person-years), resulting in an adjusted HR of 1.39 (95% CI 1.03-1.74). By contrast, there was no significant difference in the risk of IS between the exposed and reference cohorts (adjusted HR 1.11; 95% CI 0.81-1.52). The present study revealed that patients taking both clopidogrel and omeprazole was associated with an increased risk of IS.

Cardiovascular Compatibility of Proton Pump Inhibitors: Practice Recommendations

This manuscript aims to critically evaluate the current evidence regarding adverse cardiovascular effects associated with proton pump inhibitors (PPIs) in patients with coronary artery disease (CAD). It also provides guidance for the selection of the most appropriate PPI within the context of cardiovascular polypharmacy and emphasizes the importance of establishing consensus among clinicians on the need to prescribe PPIs with limited cytochrome P450 (CYP450) enzyme inhibition to reduce the risk of drug interactions. PPIs are among the most widely used drugs for the treatment of gastroesophageal reflux disease (GERD) and the prevention of gastrointestinal (GI) bleeding. The manuscript reports the proceedings from the first practice recommendations meeting on the cardiovascular compatibility of PPIs in an Indian setting. A panel of eight Indian experts in cardiology and gastroenterology reviewed 14 consensus statements. Available literature was searched and summarized, and after multiple rounds of review, consensus was achieved for these statements. Based on the available evidence, the consensus panel highlights that a PPI with minimal drug-drug interaction (DDI) is recommended, especially in patients requiring clopidogrel or polypharmacy. Rabeprazole appears to be a good option in cases where co-prescription is indicated, owing to its optimal acid suppression and minimal drug interaction profile.

Rabeprazole Coadministration Controls Ulcer Recurrence in Patients on Low-dose Aspirin Therapy: A Multicenter Prospective Study

Objective To evaluate the efficacy and safety of rabeprazole coadministration with low-dose aspirin (LDA). Methods From 2015 to 2018, we conducted a large-scale, multicenter, prospective observational study to assess the safety and efficacy of treatment with rabeprazole (5 or 10 mg/day) in combination with LDA. Results The incidence of adverse reactions was 0.73% (11/1,513 patients), with no serious adverse reactions. We found no trend toward increases in the incidence of adverse reactions with increases in treatment duration. The cumulative recurrence rate of ulcers by Week 52 (Kaplan-Meier estimates) was 3.50% (range, 1.56-7.75%). No gastrointestinal bleeding was reported. Conclusion Rabeprazole in combination with LDA appears as safe and effective in real-world situations as in clinical trials.

Prevalence and Safety of Prescribing PPIs with Clopidogrel in Palestine

BACKGROUND

Proton pump inhibitors (PPIs) are commonly prescribed medications that are thought to increase the risk of cardiovascular events because they reduce the effectiveness of clopidogrel via shared hepatic pathways.

OBJECTIVE

This study examined the prevalence of concomitant prescribing of clopidogrel/PPI among patients diagnosed with acute coronary syndrome and the adverse cardiovascular event associated with this interaction.

METHODS

A retrospective cohort study was conducted by retrieving patient data from the Nat Health Insurance claims processor database in Palestine. Adults diagnosed with Acute Coronary Syndrome (ACS) from 2019 through 2021 who were prescribed clopidogrel or clopidogrel in combination with a PPI were included in the study. Endpoints were adverse cardiac events, including readmission for revascularization during the first year of treatment.

RESULTS

The study included 443 patients; the prevalence of prescribing concomitant clopidogrel with a PPI was 74.7%, whereas 49.2% were prescribed interacting PPI (omeprazole, esomeprazole, and lansoprazole). 59 (13.3%) of participants experienced a cardiovascular event within 1 year of starting therapy, including 27 (12.4%) patients who had a cardiovascular event while taking an interacting PPI. No significant association was found between PPI administration and increased CV event risk in patients receiving concomitant clopidogrel and PPIs therapy (p = 0.579).

CONCLUSION

In this study, we observed a high prevalence of prescribing a PPI in combination with clopidogrel, regardless of the FDA recommendations. No significant increase in cardiovascular events was observed in patients receiving concomitant clopidogrel and PPI therapy.

The efficacy and safety of the short-term combination therapy with ticagrelor and PPIs or H2RA in patients with acute STEMI who underwent emergency PCI

Combination therapy with platelet inhibitors and acid-suppressive agents is recommended for patients with acute ST-segment elevation myocardial infarction (STEMI) who underwent percutaneous coronary intervention (PCI), but there remains a paucity of data to evaluate both the efficacy and safety of these combinations. In this prospective study, a total of 170 patients with acute STEMI who underwent PCI were divided into four groups: pantoprazole + ticagrelor, omeprazole + ticagrelor, ranitidine + ticagrelor, and ticagrelor only. The risk of PCI, antithrombotic efficacy, cardiac function, and main end points were evaluated and compared. No significant differences were found in infarction-related artery perfusion indexes (thrombolysis in myocardial infarction [TIMI], corrected TIMI frame count), the incidence of stent thrombosis after PCI, platelet indicators (platelet count, mean platelet volume, and platelet distribution width), platelet activation (P-selectin and glycoprotein IIb/IIIa levels), platelet aggregation (thrombelastography indicators, such as ADP% and MA_ADP ), myocardial necrosis biomarker (creatine kinase isoenzyme-MB and cardiac troponin I) levels, brain natriuretic peptide levels, the incidence of ischemic end point events, and the incidence of other tissue and organ bleeding events among the four groups. The incidence of gastrointestinal (GI) bleeding events in the proton pump-inhibitor (PPI) group was significantly lower than that in the control group, whereas in the H2 receptor antagonist (H2RA) group it was not significantly different from the control group. The short-term combination therapy with ticagrelor and PPIs or H2RA is safe and effective in patients with acute STEMI after PCI. In addition, the PPIs combined with ticagrelor could reduce the incidence of GI bleeding events without increasing the incidence of ischemic events.

Antiaggregation effect of clopidogrel in coronary heart disease patients using omeprazole

Background Antiplatelet agents used in coronary heart disease (CHD) cause gastrointestinal side effects. Omeprazole can prevent and cure these antiplatelet side effects. Clopidogrel combined with aspirin increases the risk of gastrointestinal tract ulcers and bleeding. This research studied the effect of omeprazole on the antiplatelet effect of clopidogrel. Methods CHD patients using clopidogrel and aspirin receive omeprazole 20 mg in a single dose for 10 days. Platelet antiaggregation point for clopidogrel was measured using VerifyNow P2Y12. The cutoff points used were: low on treatment platelet reactivity (LPR) <85 P2Y12 reaction unit (PRU), normal on treatment platelet reactivity (NPR) 85-208 PRU, and high on treatment platelet reactivity (HPR) >208 PRU. Results Using the paired t-test PRU points pre- and post-omeprazole were 154 ± 85.89 PRU and 169.4 ± 56.15 PRU, respectively. The PRU points were consistent or decreased from the previous PRU points below the HPR cutoff (p: 0.215; >0.05). Before omeprazole use, five patients were categorized as NPR, two patients as LPR, and three patients as HPR. After omeprazole use, two patients, each from HPR and NPR category had a PRU point >208; the rest showed results below the HPR point. Conclusions In this study the PRU points of clopidogrel after omeprazole use showed a PRU <208. The hypothesis that omeprazole may reduce the antiaggregation effect of clopidogrel as shown by the increase in PRU above the cutoff points >208 PRU (HPR) was not proven.

Acid-Suppressive Therapy and Risk of Infections: Pros and Cons

This narrative review summarises the benefits, risks and appropriate use of acid-suppressing drugs (ASDs), proton pump inhibitors and histamine-2 receptor antagonists, advocating a rationale balanced and individualised approach aimed to minimise any serious adverse consequences. It focuses on current controversies on the potential of ASDs to contribute to infections-bacterial, parasitic, fungal, protozoan and viral, particularly in the elderly, comprehensively and critically discusses the growing body of observational literature linking ASD use to a variety of enteric, respiratory, skin and systemic infectious diseases and complications (Clostridium difficile diarrhoea, pneumonia, spontaneous bacterial peritonitis, septicaemia and other). The proposed pathogenic mechanisms of ASD-associated infections (related and unrelated to the inhibition of gastric acid secretion, alterations of the gut microbiome and immunity), and drug-drug interactions are also described. Both probiotics use and correcting vitamin D status may have a significant protective effect decreasing the incidence of ASD-associated infections, especially in the elderly. Despite the limitations of the existing data, the importance of individualised therapy and caution in long-term ASD use considering the balance of benefits and potential harms, factors that may predispose to and actions that may prevent/attenuate adverse effects is evident. A six-step practical algorithm for ASD therapy based on the best available evidence is presented.

Effect of egualen sodium hydrate on small-intestinal mucosal damage induced by low-dose aspirin: a prospective randomized clinical trial

Low-dose aspirin, which is widely used to reduce the risk of cardio- and cerebrovascular thrombosis, often induces gastroenteropathy by increasing the permeability of the mucosa. However, therapeutic strategies for patients with low-dose aspirin-induced small intestinal injury have not been determined. We evaluated the preventative effect of egualen sodium hydrate, a gastro-protective agent that suppresses indomethacin-induced small-intestinal damage in rats, against small-intestinal mucosal damage induced by low-dose aspirin in healthy adult male volunteers. Participants were randomly allocated to receive aspirin 100 mg/kg daily (control group, n = 10) or aspirin 100 mg/kg plus egualen sodium 30 mg daily (egualen sodium group, n = 10). Small intestinal mucosal injury was evaluated by capsule endoscopy two weeks after initiation of drug administration. Fecal analyses (occult blood test, immunochemical test, transferrin measurement and calprotectin measurement) were carried out before and after treatment. Egualen sodium significantly suppressed the total number of small intestinal injuries detected by capsule endoscopy and the positive ratio for the fecal occult blood test. Daily use of 30 mg of egualen sodium showed a preventative effect on low-dose aspirin-induced small intestinal injury. Since acid suppression therapy was reported to exacerbate NSAIDs-induced enteropathy via dysbiosis, egualen sodium may be useful for patients treated with low-dose aspirin.

Comparison of prophylactic effect of UGIB and effects on platelet function between PPIs and H2RAs combined with DAPT: systematic review and meta-analysis

Objective

We compared prophylactic effects of proton pump inhibitors (PPIs) and histamine-2 receptor antagonists (H₂RAs) on upper gastrointestinal bleeding (UGIB) associated with dual antiplatelet therapy (DAPT) and explored this influence on platelet function.

Methods

Randomized controlled trials and cohort studies comparing PPIs with H₂RAs in adults receiving DAPT were collected from PubMed, EMBASE and Cochrane databases. Dichotomous data were pooled to obtain risk ratios (RRs) for UGIB, major adverse cardiovascular events (MACEs), poor responders to clopidogrel and rehospitalization, and continuous data were pooled to obtain mean differences (MDs) for P2Y₁₂ reaction units (PRUs), with 95% confidence intervals (CIs).

Results

Twelve clinical trials (n=3,301) met the inclusion criteria. Compared to H₂RAs, PPIs lessened UGIB (RR =0.16, 95% CI: 0.03–0.70), and there was no significant difference in the incidence of PRUs (MD =18.21 PRUs, 95% CI: −4.11–40.54), poor responders to clopidogrel (RR =1.21, 95% CI: 0.92–1.61), incidence of MACEs (RR =0.89, 95% CI: 0.45–1.75) or rehospitalization (RR =1.76, 95% CI: 0.79–3.92). Subgroup analysis confirmed fewer PRUs in the H₂RAs group compared to the omeprazole group (2 studies, n=189, MD =31.80 PRUs, 95% CI: 11.65–51.96). However, poor responder data for clopidogrel and MACEs might be unreliable because few studies of this kind were included.

Conclusion

Limited evidence indicates that PPIs were better than H₂RAs for prophylaxis of UGIB associated with DAPT and had no effect on platelet function. Further study is needed to confirm these observations.

Clinical relevance of clopidogrel-proton pump inhibitors interaction

Clopidogrel is a widely used antiplatelet agent for the secondary prevention of cardiovascular events in patients with stable coronary heart disease, acute coronary syndromes and ischemic stroke. Even though clopidogrel is safer than aspirin in terms of risk for gastrointestinal (GI) bleeding, the elderly, and patients with a history of prior GI bleeding, with Helicobacter pylori infection or those who are also treated with aspirin, anticoagulants, corticosteroids or nonsteroidal anti-inflammatory drugs are at high risk for GI complications when treated with clopidogrel. Accordingly, proton pump inhibitors are frequently administered in combination with clopidogrel to reduce the risk for GI bleeding. Nevertheless, pharmacodynamic studies suggest that omeprazole might attenuate the antiplatelet effect of clopidogrel. However, in observational studies, this interaction does not appear to translate into increased cardiovascular risk in patients treated with this combination. Moreover, in the only randomized, double-blind study that assessed the cardiovascular implications of combining clopidogrel and omeprazole, patients treated with clopidogrel/omeprazole combination had reduced risk for GI events and similar risk for cardiovascular events than patients treated with clopidogrel and placebo. However, the premature interruption of the study and the lack of power analysis in terms of the cardiovascular endpoint do not allow definite conclusions regarding the cardiovascular safety of clopidogrel/omeprazole combination. Other proton pump inhibitors do not appear to interact with clopidogrel. Nevertheless, given the limitations of existing observational and interventional studies, the decision to administer proton pump inhibitors to patients treated with clopidogrel should be individualized based on the patient’s bleeding and cardiovascular risk.

Long-term efficacy and safety of rabeprazole in patients taking low-dose aspirin with a history of peptic ulcers: a phase 2/3, randomized, parallel-group, multicenter, extension clinical trial

A 24-week, double-blind, clinical trial of rabeprazole for the prevention of recurrent peptic ulcers caused by low-dose aspirin (LDA) has been reported, but trials for longer than 24 weeks have not been reported. The aim of this study is to assess the long-term efficacy and safety of rabeprazole for preventing peptic ulcer recurrence on LDA therapy. Eligible patients had a history of peptic ulcers on long-term LDA (81 or 100 mg/day) therapy. Patients with no recurrence of peptic ulcers at the end of the 24-week double-blind phase with rabeprazole (10- or 5-mg once daily) or teprenone (50 mg three times daily) entered the extension phase. Rabeprazole doses were maintained for a maximum of 76 weeks, including the double-blind 24-week period and the extension phase period (long-term rabeprazole 10- and 5-mg groups). Teprenone was randomly switched to rabeprazole 10 or 5 mg for a maximum of 52 weeks in the extension phase (newly-initiated rabeprazole 10- and 5-mg groups). The full analysis set consisted of 151 and 150 subjects in the long-term rabeprazole 10- and 5-mg groups, respectively, and the cumulative recurrence rates of peptic ulcers were 2.2 and 3.7%, respectively. Recurrent peptic ulcers were not observed in the newly-initiated rabeprazole 10- and 5-mg groups. No bleeding ulcers were reported. No clinically significant safety findings, including cardiovascular events, emerged. The use of long-term rabeprazole 10- and 5-mg once daily prevents the recurrence of peptic ulcers in subjects on low-dose aspirin therapy, and both were well-tolerated.

Randomised clinical trial: prevention of recurrence of peptic ulcers by rabeprazole in patients taking low-dose aspirin

BACKGROUND

Few studies have evaluated the effects of rabeprazole on low-dose aspirin (LDA)-induced gastroduodenal injuries.

AIM

To conduct a randomised, double-blind, triple-dummy, active-controlled, multicentre trial, named the PLANETARIUM study, to assess the efficacy, dose-response relationship and safety of rabeprazole for peptic ulcer recurrence in Japanese patients on long-term LDA therapy.

METHODS

Eligible patients had a history of endoscopically confirmed peptic ulcers and were receiving long-term LDA (81 or 100 mg/day) therapy for cardiovascular or cerebrovascular protection. Subjects were randomly segregated into three groups receiving rabeprazole 10 mg once daily (standard dose in Japan), rabeprazole 5 mg once daily, or teprenone (geranylgeranylacetone; mucosal protective agent commercially available in Japan) 50 mg three times per day as an active control. The primary endpoint was recurrence of peptic ulcers over 24 weeks.

RESULTS

Among 472 randomised subjects, 452 subjects (n = 151, 150, 151, respectively) constituted the full analysis set. The cumulative recurrence rates of peptic ulcers over 24 weeks in the 10- and 5-mg rabeprazole groups were 1.4% and 2.8%, respectively, both of which were significantly lower than that in the teprenone group (21.7%). The cumulative occurrence rate of bleeding ulcers over 24 weeks in the teprenone group was 4.6%, while bleeding ulcers were not observed in the 10- or 5-mg rabeprazole groups. Rabeprazole was well tolerated at both doses.

CONCLUSION

Rabeprazole prevents the recurrence of peptic ulcers with no evidence of a major dose-response effect in subjects on low-dose aspirin therapy.

Effect of esomeprazole with/without acetylsalicylic acid, omeprazole and lansoprazole on pharmacokinetics and pharmacodynamics of clopidogrel in healthy volunteers

OBJECTIVE

The effect of proton pump inhibitors (PPIs) on the pharmacokinetics and pharmacodynamics of clopidogrel was assessed in two healthy volunteer crossover studies.

SUBJECTS AND METHODS

Study 1: subjects received clopidogrel alone (300-mg loading dose, then 75 mg/day for 28 days) and two of three PPIs (omeprazole 80 mg, esomeprazole 40 mg or lansoprazole 60 mg) plus clopidogrel for 29 days in three treatment periods (randomized treatment sequence assignment). Study 2: subjects received clopidogrel alone (75 mg/day for 9 days) and clopidogrel alone for 4 days followed by clopidogrel plus fixed-combination esomeprazole 20 mg/low-dose acetylsalicylic acid (ASA) 81 mg for 5 days in two treatment periods (randomized treatment sequence assignment). Pharmacokinetic effects were estimated by measuring active metabolite of clopidogrel, and pharmacodynamic effects by inhibition of adenosine diphosphate (ADP)-induced platelet aggregation.

RESULTS

There was a relative decrease of up to 50 % in exposure to the active metabolite of clopidogrel with the different PPIs (study 1), and close to 40 % with esomeprazole/low-dose ASA (study 2), compared with clopidogrel alone. There was an absolute decrease of up to 17 % in inhibition of ADP-induced platelet aggregation with co-administration of different PPIs, compared with clopidogrel alone; however, no differences in platelet inhibition were observed during co-administration with the esomeprazole/low-dose ASA fixed-dose combination.

CONCLUSION

Omeprazole, esomeprazole and lansoprazole decreased systemic exposure to the active metabolite of clopidogrel in healthy volunteers, leading to modest decreases in its antiplatelet effect. However, no apparent differences in platelet inhibition were observed when esomeprazole was co-administered with low-dose ASA as a fixed-dose combination.

The use of H2 antagonists in treating and preventing NSAID-induced mucosal damage

Pain affects the quality of life for millions of individuals and is a major reason for healthcare utilization. As populations age, medical personnel will need to manage more and more patients suffering from pain associated with degenerative and inflammatory musculoskeletal disorders. Nonsteroidal anti-inflammatory drugs (NSAIDs) are an effective treatment for both acute and chronic musculoskeletal pain; however, their use is associated with potentially significant gastrointestinal (GI) toxicity. Guidelines suggest various strategies to prevent problems in those at risk for NSAID-associated GI complications. In this article, we review the data supporting one such strategy - the use of histamine type-2 receptor antagonists (H2RAs) - for the prevention of GI adverse events in NSAID users. Older studies suggest that high-dose H2RAs are effective in preventing upper GI ulcers and dyspepsia. This suggestion was recently confirmed during clinical trials with a new ibuprofen/famotidine combination that reduced the risk of ulcers by 50% compared with ibuprofen alone.

Platelet inhibitory effect of clopidogrel in patients treated with omeprazole, pantoprazole, and famotidine: a prospective, randomized, crossover study

BACKGROUND

Concerns about an inhibitory effect of proton pump inhibitors (PPIs) on clopidogrel metabolism have been raised. Because the pharmacological effect of clopidogrel is dependent on genetically determined activity of the hepatic cytochrome P450 isoenzymes system, it is important to examine the interaction between different PPIs and high on-treatment platelet reactivity (HPR) after controlling for genetic variability. The aim of the study was to assess the effect of 2 PPIs and a histamine-2 (H2) receptor-blocker on platelet reactivity in a crossover trial where each patient was alternately treated with each drug.

HYPOTHESIS

Omeprazole reduces HPR more than other PPI or H2 blockers.

METHODS

Patients treated with aspirin and clopidogrel for at least 1 month were assigned to 3 consecutive 1-month treatment periods during which they were treated with each of the 3 study medications twice daily: omeprazole 20 mg, famotidine 40 mg, and pantoprazole 20 mg. At the end of each treatment phase, platelet function was evaluated with the Verify Now system using 2 cutoff values (>208 P2Y12 reaction units [PRUs] and >230 PRUs) for the definition of HPR.

RESULTS

Patients with HPR were older than those without HPR (62 ± 10 vs 55 ± 8 years, respectively, P = 0.03). HPR was more prevalent during omeprazole therapy compared to famotidine or pantoprazole (48%, 33%, and 31%, respectively, for the 208 PRU cutoff, P= 0.04; and 37%, 17%, and 23%, respectively, for the 230 PRU cutoff, P= 0.003).

CONCLUSIONS

After eliminating the effects of interindividual variability in clopidogrel metabolism, omeprazole therapy was associated with substantially more HPR than famotidine or pantoprazole.