Myocardial infarction aspirin effect

In a more extensive international trial, 17,187 patients were treated intravenously with streptokinase alone, aspirin alone, a combination of streptokinase and aspirin, or placebo (78). Streptokinase and aspirin were equally effective in treating acute myocardial infarction, each decreasing mortahty by 25% their combination further reduced mortahty by 42%. A significant reduction in mortahty was seen even in those patients treated up to 24 hours after the onset of symptoms. 

COX-2 inhibitors such as celecoxib are associated with adverse effects such as nephrotoxicity and a potential increased risk of myocardial infarction (see Chaps. 55 and 15 for additional information). Combination of COX-2 inhibitors with alcohol may increase GI adverse effects. All NSAIDs should be used with caution in patients with aspirin-induced asthma.31... 

Aspirin is maximally effective as an antithrombotic agent at the comparatively low dose of 81 to 325 mg per day. (The antipyretic dose of aspirin in adults is 325 to 650 mg every 4 h.) Higher doses of aspirin are actually contraindicated in patients prone to thromboembolism. At higher doses, aspirin also reduces synthesis of prostacyclin, another arachidonic acid metabolite. Prostacyclin normally inhibits platelet aggregation. The prophylactic administration of low-dose aspirin has been shown to increase survival following myocardial infarction, decrease incidence of stroke, and assist in maintenance of patency of coronary bypass grafts. 

Herlitz J, Holm J, Peterson M, Karlson BW, Haglid Evan-der M, Erhardt L. Effect of fixed low-dose warfarin added to aspirin in the long term after acute myocardial infarction the LoWASA Study. Enr Heart J 2004 25 232-9. 

Acetaminophen is similar to salicylates in that it is a useful analgesic for mild to moderate pain, with equal efficacy to aspirin, and like aspirin, it is antipyretic. However, acetaminophen exerts little if any effects on platelet aggregation and is not antiinflammatory. Thus, it is not useful for patients with arthritis or other inflammatory diseases. It is also not useful as an antithrombotic agent in the prevention of myocardial infarction or transient ischemic attacks. Acetaminophen does not produce the gastric ulceration that can occur with aspirin and is useful in patients who are salicylate sensitive or who have a history of ulcers or other gastric ulcerations. 

The sahcylates are useful in the treatment of minor musculoskeletal disorders such as bursitis, synovitis, tendinitis, myositis, and myalgia. They may also be used to relieve fever and headache. They can be used in the treatment of inflammatory disease, such as acute rheumatic fever, rheumatoid arthritis, osteoarthritis, and certain rheumatoid variants, such as ankylosing spondylitis, Reiter s syndrome, and psoriatic arthritis. However, other NS AIDS are usually favored for the treatment of these chronic conditions because of their lower incidence of GI side effects. Aspirin is used in the treatment and prophylaxis of myocardial infarction and ischemic stroke. 

Overview analyses have shown that low-dose aspirin reduces the secondary incidence of heart attack and stroke by about 25%. However, it elevates the low risk of serious gastrointestinal bleeding about twofold over placebo. Low-dose aspirin also reduces the incidence of first myocardial infarction. However, in this case, the benefit versus risk of gastrointestinal bleeding is less clear. The effects of aspirin on platelet function are discussed in greater detail in Chapter 34. 

In view of the perceived benefit of aspirin in the secondary prevention of stroke and myocardial infarction, two large trials involving physicians as subjects were initiated to study the effect of aspirin in the primary prevention of arterial thrombosis. In the American study, 22,000 volunteers (age 40 to 84 years) were randomly assigned to take 325 mg of aspirin every other day or placebo. The trial was halted early, after a mean follow-up of 5 years, when a 45% reduction in the incidence of myocardial infarction and a 72% reduction in the incidence of fatal myocardial infarction were noted with aspirin treatment. However, total mortality was reduced only 4% in the aspirin group, a difference that was not statistically significant, and there was a trend for a greater risk of hemorrhagic stroke with aspirin. Thus, the prophylactic use of aspirin in an apparently healthy population is not recommended at this time, unless there are risk factors for cardiovascular disease. 

The current thinking concerning the role of aspirin in the prevention of cardiovascular disease is that it is beneficial in the event of myocardial infarction and stroke. It is effective because, in platelets small amounts of aspirin acetylate irreversibly bind to the active site of thromboxane A2, a potent promoter of platelet aggregation. 

In the case of aspirin, there are numerous reports of beneficial effects of low-dose aspirin in the secondary prophylaxis of cardiovascular disease (myocardial infarction and stroke). Aspirin clearly reduces the risk of myocardial infarction and stroke among patients who already have manifestations of cardiovascular disease. 

Lewis HD Jr, Davis JW, Archebald DG, et al. Protective effects of aspirin against acute myocardial infarction and death in men with unstable angina results of a veterans administration cooperative study. N Engl J Med 1983 309 396-403. 

De Caterina R, Giannessi D, Boem A, et al. Equal antiplatelet effects of aspirin 50 or 324mg/day in patients after acute myocardial infarction. Thromb Haemost 1985 54 528-532. 

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