Heart Attack Treatment (cont.)
Glycoprotein IIb/IIIa inhibitors
The glycoprotein IIb/IIIa inhibitors such as abciximab (Reopro) and
eptifibatide (Integrilin) prevent aggregation of platelets by inhibiting the
glycoprotein receptors on the platelets. They are the most potent anti-platelet
agents, approximately 9 times more potent than aspirin, and three times more
potent than the thienopyridines. The glycoprotein IIb/IIIa inhibitors are also
the most expensive anti-platelet agents. The currently FDA-approved glycoprotein
IIb/IIIa inhibitors have to be given intravenously. They usually are given along
with aspirin and heparin. They are quick acting; their maximal anti-platelet
effects are achieved within minutes of infusion. These inhibitors have become
important in the treatment of patients with heart attacks, patients with
unstable angina, and patients undergoing PTCA with or without stenting. Numerous
studies have shown that glycoprotein IIb/IIIa inhibitors:
- Decrease the size of the blood clot blocking the
coronary arteries, thus improving blood flow, limiting damage to heart muscle,
and improving survival among patients with heart attacks
- Decrease the incidence of heart attacks and improve
survival among patients with unstable angina
- Prevent the formation of blood clots inside coronary stents and in
coronary arteries unblocked by PTCA, thus decreasing the incidence of heart
attacks and improving survival, specifically, when given intravenously at the time of PTCA and
stenting and followed by oral aspirin and clopidogrel
The major risk of glycoprotein IIb/IIIa inhibitors is bleeding. Therefore,
patients on heparin, aspirin, and glycoprotein IIb/IIIa inhibitors have to be
monitored closely for bleeding. Recent studies have demonstrated equal efficacy
of abciximab and eptifibatide. Eptifibatide is shorter acting than abciximab. In
the event of major bleeding, the anti-platelet effect of eptifibatide can be
reversed within hours of stopping the intravenous infusion, while the
anti-platelet effect of abciximab will last much longer. Sometimes, transfusions
of platelets are necessary to treat major bleeding due to abciximab.
An uncommon side effect of glycoprotein IIb/IIIa inhibitors is
the development of low platelet counts (thrombocytopenia). Thrombocytopenia
can increase the risk for bleeding and, in rare instances, may actually cause blood to
clot. Thus, patients receiving glycoprotein IIb/IIIa inhibitors should have
their platelet counts monitored closely.
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