After Stent or Angioplasty:
Effient (Prasugrel) Bests Plavix (Clopidogrel) for Patients with
High
Platelet Reactivity
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May 5, 2011 --
In the current issue of JACC Cardiovascular Interventions,
a
small study from Greece highlights an ongoing controversy over
the optimal antiplatelet therapy for patients after angioplasty
or stenting (a.k.a. percutaneous coronary intervention or PCI).
Antiplatelet therapy is necessary after stent placement to
lower the risk of blood clotting inside the stent: an adverse
event, known as stent thrombosis, that can trigger a heart
attack. |
The standard therapy has been aspirin plus
clopidogrel (brand name Plavix) for 2-6 months after bare metal
stents and a year or more after drug-eluting stents. But in July
2009, the
FDA
approved a new and more potent antiplatelet
drug: prasugrel (brand name Effient). One caution about prasugrel
has been that, because it is more powerful, it may have pose an increased
risk of bleeding complications for the patient.
However, a number of recent studies have revealed
that some patients are non-responders, or low-responders, to clopidogrel
-- a drug that needs to be metabolized before it can be effective.
A platelet reactivity test, often the VerifyNow assay from Accumetrics,
is sometimes given where there are questions. High On-Treatment Platelet
Reactivity (HTPR) may be a risk factor for stent thrombosis. Additionally,
many of
these low-or-no responders also have been shown to have a particular
genetic
marker,
the CYP2C19*2
loss-of-function
allele, determined through genetic testing. (For more information
on these issues, read Angioplasty.Org's exclusive
interview with Dr. Eric Topol.)
In this current study, the team headed by Dr. Dimitrios
Alexopoulos, Department of Cardiology, Patras University Hospital,
Patras, Greece, measured the platelet reactivity of 210 patients
after PCI and found that one-third (71 patients) had high platelet
reactivity, defined as a PRU of > 235. The patients were
also genotyped to see if they had the CYP2C19*2
loss-of-function
allele. The 71 patients were then randomized
to a double-dose of clopidogrel (150mg) or the standard
dose of prasugrel (10mg) and measured at 30 and then at 60 days.
The results of this small study were significant:
all patients achieved an almost five-fold reduction in platelet
reactivity across the board with prasugrel vs. clopidogrel (7.5%
vs. 35.8%). Looking at only those patients with the
2C19*2 carrier, the reduction was even higher -- nine-fold (5.3%
vs.
47.4%). This study, although small in number and therefore limited,
bolsters the efficacy of individualizing antiplatelet therapy
in patients who have high on-treatment platelet reactivity after
stenting.
The authors conclude:
"For patients with HTPR after standard clopidogrel
treatment after PCI, prasugrel 10 mg/day is more effective than
clopidogrel 150 mg/day in reducing PR. This effect is more prominent
in patients
carrying 1 loss-of-function CYP2C19*2 allele. Hence, in HTPR
patients, genotyping guidance might be helpful only in case an
increased
clopidogrel maintenance dose is considered. Measurement of platelet
function
in a post-PCI patient and subsequent treatment with prasugrel—if
found with HTPR—seems to be the most effective strategy to overcome
low responsiveness."
Reported by Burt Cohen, May 5, 2011
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