(Circulation. 2006;113:e655-e658.)
© 2006 American Heart Association, Inc.
Clinician Update |
From the Cardiovascular Division, Brigham and Womens Hospital, Harvard Medical School, Boston, Mass.
Correspondence to Samuel Z. Goldhaber, MD, Cardiovascular Division, Brigham and Womens Hospital, 75 Francis St, Boston, MA 02115. E-mail sgoldhaber{at}partners.org
| Introduction |
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| Background |
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The use of aspirin compared with placebo reduces the risk of myocardial infarction, stroke, or death from vascular causes by
25%.1 In the Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events (CAPRIE) trial, administration of clopidogrel decreased the relative risk of vascular events by 8.7% compared with aspirin.2 The addition of clopidogrel to aspirin in patients with acute coronary syndrome reduces the risk of reinfarction, stroke, and death by 20% compared with aspirin alone.3
The net benefit from using dual antiplatelet therapy in high-risk vascular disease patients comes at the cost of increased gastrointestinal (GI) complications. Major complications include gastroduodenal ulcerations that can lead to GI hemorrhage, perforation, and death. Minor complications include dyspepsia, pill esophagitis, subepithelial hemorrhages, erosions, and ulcerations in the stomach and duodenum. Patients at especially high risk for GI complications while on antiplatelet therapy are the elderly; those with a history of gastroduodenal ulcers, gastroesophageal reflux disease, esophagitis, untreated Helicobacter pylori infection, intestinal polyps, or cancer; and those using concomitant anticoagulants, steroids, or nonsteroidal anti-inflammatory drugs.
| Risk of GI Complications With Aspirin |
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While examining the relationship between aspirin intake and hospitalization with peptic ulcer bleeding, Weil et al5 found that all doses of aspirin are associated with an increased risk of GI bleeding. The risk of GI bleeding was dose related: odds ratio 2.3 for 75 mg/d, 3.2 for 150 mg/d, and 3.9 for 300 mg/d. The risk of upper GI bleeding for plain, enteric-coated, or buffered aspirin did not differ.9 Long-term aspirin therapy, even at a low dose (50 to 162.5 mg/d), may cause overt GI bleeding.10
| Risk of GI Complications With Clopidogrel |
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| Risk of GI Complications With Dual Antiplatelet Therapy |
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200 mg) given with placebo, bleeding was higher (3.7%) than the risk of GI bleeding with the combination of clopidogrel and aspirin in the lowest-dose (
100 mg) group (3.0%). | Efficacy of Dual Antiplatelet Therapy |
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Aspirin and clopidogrel "resistance" has been increasingly identified with the availability of point-of-care platelet aggregation tests. Many patients on aspirin and clopidogrel therapy do not achieve the desired level of platelet inhibition. One way to overcome aspirin and clopidogrel resistance is to use higher loading and maintenance doses.
The inhibition of platelet aggregation by clopidogrel is dose dependent. A higher loading dose of clopidogrel is now being used more often than the conventional 300-mg dose because of more rapid and higher levels of platelet inhibition. Patti et al16 reported that a 600-mg loading dose was safe and more effective in reducing periprocedural infarction than a 300-mg loading dose.
| Monitoring and Diagnosis of GI Complications |
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A noninvasive imaging test that does not require sedation to diagnose occult GI complications is the PillCam ESO capsule endoscopy (Given Imaging, Inc, Norcross, Ga). The disposable, ingestible PillCam ESO endoscope is an 11x26-mm capsule. It acquires video images from both ends of the device during passage through the esophagus. The capsule transmits the acquired images via a digital radiofrequency communication channel to an external data recorder unit. On completion of the examination, the accumulated data are processed with image reconstruction and are interpreted by a GI specialist. The PillCam is excreted in the feces and does not need to be retrieved.
| Is GI Prophylaxis Needed for Dual Antiplatelet Therapy? |
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Prophylactic acid-suppressive therapy is beneficial in the prevention of upper GI complications. Two major classes of protective agents are (1) H2 antagonists and (2) proton pump inhibitors (PPIs).
H2 antagonists reversibly block H2 receptors on the basolateral membrane of gastric parietal cells.17 Until the early 1990s, H2 antagonists were the mainstay of pharmacotherapy for the prevention and management of upper GI bleeding. Between 1984 and 2000, 32 randomized controlled trials compared H2 antagonists with placebo.18 Agents evaluated in these studies included cimetidine, ranitidine, and famotidine. Many were limited by a small sample size and unsatisfactory study design.
Factors limiting the utility of H2 antagonists include the development of tachyphylaxis, the need for dosage adjustment in renal insufficiency, and side effects such as thrombocytopenia and mental status abnormalities.
The introduction of PPIs has led to a safer and more effective strategy in the prevention and management of GI ulceration.17 PPIs irreversibly inhibit hydrogen ion pumps in gastric parietal cells. PPIs block the final step of acid production, negate stimulation of gastric secretion, and lead to prolonged acid suppression.
Yeomans et al19 showed that omeprazole, a PPI, is more effective than H2 receptor antagonists in suppressing gastric acid, preventing ulcers, and healing ulcers that are related to chronic use of nonsteroidal anti-inflammatory drugs such as aspirin.
Chan et al20 randomized 320 patients with vascular disease who had previous GI bleeding while taking aspirin to clopidogrel alone versus aspirin plus esomeprazole. The cumulative incidence of recurrent ulcer bleeding over a 12-month period in this study was 8.6% in patients who received clopidogrel and 0.7% in patients who received aspirin and esomeprazole.
Is it justifiable to start all patients requiring dual antiplatelet therapy on prophylactic acid-suppressive therapy? The risk of an adverse GI event in antiplatelet users depends on the patients baseline risk, added risk associated with the dose and duration of aspirin and clopidogrel therapy, and protection conferred by cotherapy with acid-suppressive agents. Physicians who prescribe antiplatelet therapy should be aware of an individual patients risk of GI complications. During every office visit, physicians should ask about new or worsening GI symptoms. Initiating prophylactic acid-suppressive therapy may be reasonable in high-risk patients for the duration of antiplatelet therapy; however, clinical trials are urgently needed to confirm or refute this hypothesis.
Patients who undergo PCI for acute coronary syndrome are usually discharged on 5 classes of medications: aspirin, clopidogrel, a ß-blocker, an angiotensin-converting enzyme inhibitor, and a statin. These medications reduced the morbidity and mortality rates in large-scale randomized controlled trials. Before subjecting PCI patients to a routine prophylactic acid-suppressive therapy as the sixth standard medication, we need large-scale trials to assess cost-effectiveness and to determine whether the benefit outweighs the risks of polypharmacy.
| Case |
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| References |
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2. CAPRIE Steering Committee. A randomized, blinded, trial of Clopidogrel Versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE). Lancet. 1996; 348: 13291339.[CrossRef][Medline] [Order article via Infotrieve]
3. Yusuf S, Zhao F, Mehta SR, Chrolavicius S, Tognoni G, Fox KK. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation. N Engl J Med. 2001; 345: 494502.
4. Cohen MM, MacDonald WC. Mechanism of aspirin injury to human gastroduodenal mucosa. Prostaglandins Leukot Med. 1982; 9: 241255.[Medline] [Order article via Infotrieve]
5. Weil J, Colin-Jones D, Langman M, Lawson D, Logan R, Murphy M, Rawlins M, Vessey M, Wainwright P. Prophylactic aspirin and risk of peptic ulcer bleeding. BMJ. 1995; 310: 827830.
6. Sorensen HT, Mellemkjaer L, Blot WJ, Nielsen GL, Steffensen FH, McLaughlin JK, Olsen JH. Risk of upper gastrointestinal bleeding associated with use of low-dose aspirin. Am J Gastroenterol. 2000; 95: 22182224.[Medline] [Order article via Infotrieve]
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8. Farrell B, Godwin J, Richards S, Warlow C. The United Kingdom Transient Ischaemic Attack (UK-TIA) aspirin trial: final results. J Neurol Neurosurg Psychiatry. 1991; 54: 10441054.
9. Kelly JP, Kaufman DW, Jurgelon JM, Sheehan J, Koff RS, Shapiro S. Risk of aspirin-associated major upper-gastrointestinal bleeding with enteric-coated or buffered product. Lancet. 1996; 348: 14131416.[CrossRef][Medline] [Order article via Infotrieve]
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16. Patti G, Colonna G, Pasceri V, Pepe LL, Montinaro A, Di Sciascio G. Randomized trial of high loading dose of clopidogrel for reduction of periprocedural myocardial infarction in patients undergoing coronary intervention: results from the ARMYDA-2 (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) study. Circulation. 2005; 111: 20992106.
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