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48. Will COX-2 inhibitors survive the current focus of attention?
Worldwide the lay press and electronic media have made patients and doctors
aware of the concerns about increased risk of myocardial infarction and
stroke in patients taking Vioxx (rofecoxib), and of Merck's decision to
withdraw this blockbuster drug from the market (>10 million scripts
per month in the US, annual sales >$1bn, >$100mill spent per annum
in direct-to-consumer advertising). More recently, Celebrex (celecoxib)
has also hit the headlines after Pfizer's concerns and decision to stop
direct-to-consumer advertising. These appear to be responsible actions
on the part of the regulators and manufacturers, but review of the literature
reveals that concerns about the cardiovascular safety of this class of
drugs were already raised at the turn of the new century. Researchers
had been aware of the results of early studies showing either statistically
significant differences or tendencies towards greater cardiovascular risks
with these drugs and had called for specific studies that were sufficiently
powered to investigate these risks more fully. Pathophysiologically their
concerns were based on the fact that the coxibs inhibited prostaglandin
I2 , previously shown to be the predominant cyclo-oxygenase in endothelium,
an inhibitor of platelet aggregation, a vasodilator and preventor of profileration
of vascular smooth muscle. Clearly, if these were the actions of COX-2,
then inhibition could present a risk to patients, certainly to those with
cardiovascular disease. Furthermore, COX-2 inhibitors would leave COX-1
intra-platelet activity untouched (i.e. thromboxane induced platelet aggregation,
vasoconstriction and vascular proliferation) i.e. they would block favourable
cardiovascular processes, leaving the less favourable to act unopposed.
At this stage it would seem that the whole class is under review, and
while the general instructions to doctors and patients are along the lines
of avoiding the use of the drugs in the presence of established or potential
cardiovascular disease, because the likelihood of concurrent diseases
is so high in the target population one may well see manufacturers, doctors
and patients reviewing the situation and opting for less risky alternatives.
Read more:
New Engl J Med 2004;351:1707-9 and 1709-11
JAMA 2001;286:954-9
Natl Rev Drug Discov 2003;2:879-90
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