Aspirin is the most widely used
platelet aggregation inhibiting agent. It is simple, safe, and very cost-effective.
Although effective, aspirin is a weak platelet inhibitor. It affects only one of the
pathways to platelet aggregation—the cyclo-oxygenase pathway. Ticolpidine [Ticlid]
and the recently introduced clopidogrel affect another pathway. Clopidogrel lacks the
neutropenic side effect of ticlopidine and may be superior to aspirin for TIA, peripheral
vascular disease, and after coronary stenting. However, after myocardial infarction
clopidogrel did not show any advantage over aspirin.
Recently, agents blocking the final common pathway of aggregation have been developed.
They inhibit the platelet fibrinogen receptor.
Terminology:
Integrin is a platelet membrane glyco-protein which receives fibrinogen.
Abciximab is a monoclonal antibody to the integrin.
Eptifibatide and tirofiban are non-antibody compounds which block integrin.
This issue of NEJM includes two large clinical trial 1,2 which indicate a 30 to 20%
reduction in urgent revascularization, myocardial infarction, or death in patients
undergoing coronary intervention for refractory unstable angina and elective, urgent, or
emergency coronary interventions with balloon angioplasty, coronary atherectomy, or laser
ablation.
"Unstable angina has become one of the commonest reasons for admission to cardiology
units and most patients seen in primary and secondary care hospitals without angioplasty
facilities. If the efficacy and safety of glycoprotein IIb/IIIa inhibitors in
conservatively treated unstable angina is confirmed, it means that a new and better
antiplatelet strategy for this disorder becomes available."
Lancet May 17, 1997; 349: 1409-10 Commentary from Univ. Hospital Nijmegen, Netherlands
"Randomized Placebo-controlled Trial of Effect of Eptifibatide on Complications of
Percutaneous Coronary Intervention (IMPACT)" — Lancet May 17, 1997; 349:
1422-1428
"Randomized Placebo-controlled Trial of Abciximab before and during Coronary
Intervention in Refractory Unstable Angina: The CAPTURE Study" Lancet May 17, 1997;
349: 1428-35
Other studies have reported increased benefit of these drugs in patients with unstable
angina or non-Q wave MI when compared with heparin. RTJ
Comment: IIb/IIIa designates the 2 arms of the glycoprotein inserted into the
surface of platelets. The complex is termed "integrin". It constitures the
receptor to which fibrinogen is bound, forming the final common pathway for platelet
aggregation.
I could not find out how the term abciximab was coined—nor how to pronounce it.
Someone help me!
I abstracted this commentary to become attuned for future developments. RTJ
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