Summary and Conclusions
Low-dose aspirin, defined as 75–325 mg daily, offers clearcut benefit in the prevention of cardiovascular events in patients with prior cardiovascular disease and in those whose clinical characteristics predict a moderate-high risk of developing cardiovascular events. The main concern regarding the use of aspirin is the potential for developing serious GI events, such as bleeding. Even at recommended doses, aspirin increases the risk of GI bleeding by approximately twofold. However, the annual incidence of GI bleeding with these doses is relatively low. Pooled estimates from randomized, placebo-controlled trials suggest that the annual incidence of major GI bleeding that can be ascribed to use of low-dose aspirin (i.e. the increment above the placebo or 'no aspirin' group) is 0.12%.[20] This means that 833 patients would need to be treated with low-dose aspirin rather than no aspirin to cause an additional episode of major GI bleeding over 1 year. When the development of any degree of GI bleeding with doses of aspirin up to 1500 mg per day (well above the recommended cardioprotective dose) is assessed, the number needed to harm at 1 year is reported to be 247.[19]
The U.S. Preventive Services Task Force concluded that the benefit–risk balance with low-dose aspirin is most favourable in patients with a predicted 5-year risk for coronary heart disease ≥3%.[61] However, their recommendation was based on an assumed annual increased incidence of major GI bleeding of 0.06% from five primary prevention randomized trials – a rate somewhat lower than the results from other systematic reviews. Alternatively, the American Heart Association recommends low-dose aspirin be considered in a higher-risk group (10-year risk ≥10%) to improve the likelihood of a positive balance of benefit vs. risk.[5]
The clinical characteristics that portend an increased risk of GI bleeding with low-dose aspirin are not as well defined as they are for full-dose NSAIDs. Limited information does suggest that prior history of ulcers or GI bleeding, the use of corticosteroids or anticoagulant therapy, and the addition of a non-aspirin NSAID all significantly increase the risk. Surprisingly, age has not been documented to increase the risk with low-dose aspirin, in contrast to studies with full-dose NSAIDs. However, older patients taking low-dose aspirin do have a greater risk of GI bleeding due to the marked increase in baseline risk of bleeding with increasing age. The combination of low-dose aspirin plus another NSAID increases the risk of GI bleeding by two- to fourfold. The addition of a COX-2-specific inhibitor also increases the risk of GI injury more than additively – to approximately the level of a non-selective NSAID. However, some studies suggest that the combination of a COX-2-specific inhibitor and low-dose aspirin may have lower risk than the combination of a non-selective NSAID and low-dose aspirin.
In conclusion, when determining whether low-dose aspirin is appropriate for an individual patient, the risk of clinical events such as GI bleeding must be weighed against the cardiovascular benefit. In cases where the risk of a cardiovascular event is moderate or high based on prior cardiovascular events or an increased cardiovascular risk score, the benefits of treatment are expected to outweigh the risk.[4] In patients with low cardiovascular risk, the use of low-dose aspirin may be anticipated to cause an excess of GI events.
Read full Article - http://www.medscape.com/viewarticle/545101_print
No comments:
Post a Comment