Antithrombotics are drugs like aspirin, clopidogrel and vitamin K antagonists which are often used to limit blood clotting after a heart attack. Antithrombotics are also used routinely in atrial fibrillation and after coronary stenting. With an aging population, all these conditions are getting more common and so, too, is the use of antithrombotics. Although they can be life-saving, antithrombotics must be used with care because they also carry the side effect of causing bleeding (because they thin the blood). Bleeding caused by antithrombotics can actually increase the risk of heart attack and stroke for a number of possible reasons. That is, blood transfusions needed because of bleeding might have an adverse effect, those most likely to bleed are the sicker patients, and also bleeding leads to discontinuation of antithrombotics which, in itself, poses a risk.

Therefore, it is important to assess the safety of antithrombotics used both alone and in combination. Researchers in Denmark now report a study of over 40,000 patients admitted to hospital with a heart attack. They were divided into the following groups according to the therapy received: aspirin, clopidogrel, vitamin K antagonist alone, aspirin plus vitamin K antagonist, clopidogrel plus vitamin K antagonist, triple therapy with all three drugs.

The risk of hospital admission for non-fatal bleeding increased with the number of antithrombotics administered. The risk was increased four times on triple therapy compared to aspirin alone. A similar increased risk was observed for clopidogrel plus vitamin K antagonist. Hospital admission for bleeding associated with antithrombotic treatment was associated with a three times increased risk of death or recurrent heart attack. Therefore, the authors conclude, triple therapy or dual therapy with clopidogrel and a vitamin K antagonist should only be prescribed after a very careful risk assessment. Of course, newer antithrombotics and more targeted approaches to prescription may tip the benefit-risk equation more in the patient’s favor. But the prescription of the right antithrombotics will remain a tough clinical challenge.

Source:

Sørensen R et al Risk of bleeding in patients with acute myocardial infarction treated with different combinations of aspirin, clopidogrel, and vitamin K antagonists in Denmark: a retrospective analysis of nationwide registry data The Lancet December 12 2009;374:1967-74