Review of antiplatelet therapy

In this week’s JAMA are several articles dealing with stroke, stroke prevention and antiplatelet therapy. Tran and Anand review oral antiplatelet therapy in cerebrovascular disease, coronary artery disease and peripheral arterial disease. They looked at trials involving antiplatelet therapy in patients with documented vascular disease (stroke, TIA, coronary disease, peripheral arterial disease). Some of the main points that emerged are:

  • In patients with vascular disease, antiplatelet therapy leads to a risk reduction for vascular events of 20-30% vs. placebo.
  • Aspirin vs. plavix: The CAPRIE trial compared 325 mg of aspirin to 75 mg clopidogrel in almost 20,000 patients. Plavix was modestly superior to aspirin overall, with a risk reduction of 8.7%. The cost of plavix is much greater than that of aspirin, however, and the benefit is less than the benefit achieved by either drug alone over placebo (in the 20-30% range); the authors of this review suggest that, in most cases, either drug may be used for initial, secondary prevention.
  • Aspirin plus plavix: Greater bleeding risk. Not more effective than clopidogrel alone in the setting of stroke/TIA (MATCH trial); more effective than aspirin alone in unstable coronary syndrome patients; more studies ongoing in other CAD patients; recommended in patients after unstable angina and after percutaneous coronary interventions (aspirin indefinitely; clopidogrel for 12 mos, possibly longer).
  • Persantine (dipyridamole): One large trial of extended-release dipyridamole (ER-DP) in patients with stroke or TIA showed benefit of aspirin plus ER-DP above either drug alone. The theory is that ER-DP is superior to short-acting dipyridamole, which is the basis for the combination drug Aggrenox (aspirin plus ER-DP), but the evidence is based on this one trial, and other trials are still ongoing. No evidence yet for effectiveness in CAD patients, and theoretical concern about deleterious coronary vasodilation, particularly with short-acting dipyridamole.
  • Treatment failures on monotherapy (recurrent events): In general, patients on aspirin add or switch to clopidogrel; patients on clopidogrel add aspirin, but several variants depending on types of events. See article for details.

I found this review to be quite helpful. It applies mainly to the non-acute-coronary-syndrome patients. Another article in the same issue of JAMA deals with ACS patients in greater detail.

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