delays the start of the clotting process. Antiplatelet
agents often are part of an ANTICOAGULATION THER-
APYregimen, in combination with anticoagulant
medications.
The most commonly used antiplatelet agent is
low-dose aspirin, which health experts recom-
mend for people who have increased risk for car-
diovascular disease or who have already had heart
attack or ischemic stroke. Like anticoagulants,
antiplatelet agents require close monitoring to
maintain therapeutic levels. Three antiplatelet
agents are injectable only—abciximab (Rheopro),
eptifibatide (Integrilin), and tirofiban (Aggras-
tat)—which doctors use during ANGIOPLASTYand
sometimes other CARDIAC CATHETERIZATION proce-
dures. The oral antiplatelet agent cilostazol (Pletal)
also acts to dilate the blood vessels, so doctors
often prescribe it to treat intermittent claudication.
Doctors typically prescribe antiplatelet agents to
prevent clots from forming in people who have
PVD, CAD, valvular heart disease, prosthetic heart
valves, PACEMAKER or IMPLANTABLE CARDIOVERTER
DEFIBRILLATOR(ICD), or who have had heart attack,
stroke, or certain kinds of heart surgery. The most
significant side effect of antiplatelet agents is
excessive bleeding. Over-the-counter NONSTEROIDAL
ANTI-INFLAMMATORY DRUGS(NSAIDS) such as ibupro-
fen, and the herbal product ginkgo biloba, also
have mild antiplatelet activity; it is important to
check with the doctor or pharmacist before taking
them with prescribed antiplatelet agents.
COMMON ANTIPLATELET AGENTS
abciximab (Rheopro) cilostazol (Pletal)
clopidogrel (Plavix) dipyridamole (Persantine)
eptifibatide (Integrilin) sulfinpyrazone (Anturane)
ticlopidine (Ticlid) tirofiban (Aggrastat)
Beta BlockersBeta blockers, also called beta adrenergic antago-
nist medications or class II antiarrhythmics, block
beta receptors in the cells from binding with epi-
nephrine. Beta receptors are specific to the arteries
and MYOCARDIUM, so the actions of beta blockers
are selective and specific to these sites. In the
heart, beta blockers slow the conduction of electri-
cal impulses, which slows the heart rate and
reduces the amount of blood the heart pumps
(CARDIAC OUTPUT). These effects result in lowered
blood pressure and also reduced cardiac workload,
which relieves angina pectoris. In the arteries,
beta blockers cause smooth muscle tissue to relax,
which dilates the arteries to decrease the resist-
ance blood encounters to lower blood pressure.
Most beta blocker medications thus do not have
the systemic or generalized effects of alpha block-
ers, though a few of the beta blockers (notably
propanolol and sotalol) also have some alpha
antagonist activity as well and may have mild sys-
temic effects.
There are two kinds of beta receptors, beta 1
and beta 2. Muscle cells in the myocardium and
NERVEcells that regulate heart rate contain prima-
rily beta 1 receptors. Peripheral arteries and arteri-
oles contain primarily beta 2 receptors. Different
beta blocker drugs target either beta 1 or beta 2
receptors. The smooth muscle cells in the airways
also contain beta 2 receptors, so beta blockers that
affect beta 2 receptors in the blood vessels also
affect the airways. Medications to treat ASTHMA
may interact with beta blockers taken to treat car-
diovascular conditions. Beta blockers prescribed
for other conditions such as asthma, BENIGN PRO-
STATIC HYPERTROPHY (BPH), migraine headaches,
GLAUCOMA, and essential tremor may also affect
cardiovascular function.Do not suddenly stop taking a beta
blocker, as doing so may cause intensi-
fied ANGINA PECTORISand increased risk
for HEART ATTACK.Beta blockers are the “workhorse” drugs in car-
diology, treating a broad spectrum of cardiovascular
conditions. Doctors prescribe beta blockers to treat
hypertension, heart failure (especially congestive
heart failure), atrial fibrillation, mild to moderate
ventricular tachycardia, CARDIOMYOPATHY, angina
pectoris, and to improve survival following heart
attack. The most common side effects are fatigue
and sleepiness, which generally improve with tak-
ing the medication over time. Beta blockers may
cause erectile dysfunction in men and diminished
sexual response in women. CAFFEINEand antihista-
mines (such as in cold and allergy products) inten-
sify, and ALCOHOLdiminishes, the effects of beta
blockers. Beta blockers may interfere with the
actions of oral ANTIDIABETES MEDICATIONS.medications to treat cardiovascular disease 79