Facts on File Encyclopedia of Health and Medicine

COMMON ALPHA BLOCKERS

clonidine (Catapres) doxazosin (Cardura)
guanabenz (Wytensin) guanfacine (Tenex)
labetalol (Normodyne) methyldopa (Aldomet)
phenoxybenzamine (Dibenzyline) prazosin (Minipress)
terazosin (Hytrin)

Angiotensin II Receptor Blockers (ARBs)

Angiotensin II receptor blockers, also called
angiotensin II receptor antagonists or ARBs, pre-
vent the enzyme angiotensin II from binding with
cells the walls of the arteries. Angiotensin II is a
powerful endogenous vasoconstrictor (substance
the body makes to narrow the blood vessels) that
raises blood pressure. Preventing its actions
relaxes and dilates the arteries, reducing the resist-
ance blood encounters flowing through them and
lowering blood pressure.

Pregnant women should not take

angiotensin II receptor blockers (ARBs)

during the second and third trimesters

of PREGNANCY, as these drugs may cause

harm or death to the fetus.

ARBs may be the first-line choice to treat
hypertension, depending on the person’s overall
health profile and other medications. ARBs do not
cause the cough and other side effects that can be
troublesome with ACE inhibitors, though they do
put more strain on the kidneys. The most com-
mon side effect with ARBs is headache, especially
with losartan. Other side effects, though uncom-
mon, may include anxiety, fatigue, and gastroin-
testinal upset.

COMMON ANGIOTENSIN II RECEPTOR BLOCKERS
candesartan (Atacand) eprosartan (Teveten)
irbesartan (Avapro) losartan (Cozaar)
olmesartan medoxomil (Benicar) tasosartan (Verdia)
telmisartan (Micardis) valsartan (Diovan)

Anticoagulants

People commonly refer to anticoagulant drugs as
“blood thinners” though this is somewhat of a
misnomer. The first stage of clotting, which anti-
coagulants delay, is a thickening of the blood as
CLOTTING FACTORS begin causing cells to stick
together. Anticoagulants prevent the body from

processing vitamin K, which interferes with the

blood’s ability to activate clotting factors. Heparin,

low molecular weight heparin (LMWH), and fon-

daparinux are injectable anticoagulants that are

relatively short-acting though have cumulative

effects when administered for extended periods of

time. Surgeons use anticoagulants to completely

suppress the blood’s clotting ability during opera-

tions that require CARDIOPULMONARY BYPASS. War-

farin (Coumadin) is currently the only oral

anticoagulant available, though research contin-

ues to search for alternatives. Anticoagulants are

NTI drugs that require continual monitoring to

maintain therapeutic levels.

Women who are pregnant or planning

to become pregnant should not take

warfarin, as it can cause birth defects

(highest risk during first trimester).

Doctors prescribe anticoagulant medications to

prevent blood clots from forming, typically to pre-

vent DEEP VEIN THROMBOSIS(DVT) and PULMONARY

EMBOLISMin PERIPHERAL VASCULAR DISEASE(PVD) with

INTERMITTENT CLAUDICATION, and to prevent heart

attack and stroke. Anticoagulants cannot dissolve

clots that already exist (though thrombolytic

agents can). The most significant side effect is

excessive bleeding. Anticoagulants can interact

with numerous medications. Foods high in vita-

min K (such as dark green leafy vegetables) may

increase the blood’s clotting capability.

COMMON ANTICOAGULANTS

heparin fondaparinux (Arixtra)

warfarin (Coumadin)

LMWHs:

ardeparin (Normiflo) dalteparin (Fragmin)

enoxaparin (Lovenox) nadroparin (Fraxiparine)

reviparin (Clivarine) tinzaparin (Innohep)

Antiplatelet Agents

Antiplatelet agents also interfere with the blood’s

ability to clot by blocking platelets, the cells that

initiate clotting, from aggregating or sticking

together. PLATELET AGGREGATIONsets in motion the

sequence of chemical interactions that activate

clotting factors; blocking PLATELET aggregation

78 The Cardiovascular System