Encyclopedia of Health and Medicine

80 The Cardiovascular System
COMMON BETA BLOCKERS
acebutolol (Sectral)
atenolol (Tenormin)
betaxolol (Kerlone)
bisoprolol (Zebeta)
carteolol (Cartrol)
esmolol (Brevibloc)
metoprolol (Lopressor, Toprol) nadolol (Corgard)
penbutolol (Levatol)
pindolol (Visken)
propranolol (Inderal)
timolol (Blocadren)
Calcium Channel Blockers
Calcium channel blockers, also called calcium
channel antagonists, limit the amount of calcium
that enters contractile cells. Two of the commonly
prescribed calcium channel blockers act nearly
exclusively on the heart (myocardial cells), diltiazem
and verapamil. Cardiologists prescribe these
drugs, also identified as class IV antiarrhythmics,
to treat atrial fibrillation, PAT, hypertrophic cardiomyopathy,
and angina pectoris. The other calcium
channel blockers, sometimes called
dihydropyridine calcium channel blockers, act primarily
on the peripheral arteries, causing them to
relax and dilate. This lowers resistance for blood
flow and reduces blood pressure. Cardiologists
prescribe these calcium channel blockers to treat
hypertension, angina pectoris without arrhythmia,
and RAYNAUD’S SYNDROME. Doctors use nimodipine
following stroke to reduce the risk of arterial
spasm and resulting HEMORRHAGE, as it affects primarily
the arteries in the BRAIN.
Women who are pregnant or planning
to become pregnant should not take
calcium channel blockers, as these
drugs can cause serious birth defects
and STILLBIRTH.
COMMON CALCIUM CHANNEL BLOCKERS
amlodipine (Norvasc, Lotrel) diltiazem (Cardizem, Cartia,
felodipine (plendil)
Dilacor, Diltia, Tiazac)
isradipine (DynaCirx)
nicardipine (Cardene)
nifedipine (Adalat, Procardia) nimodipine (Nimotop)
verapamil (Calan, Covera, nisoldipine (Sular)
Isoptin, Verelan)
Side effects that may occur when taking calcium
channel blockers include headache, gastrointestinal
upset, fatigue, and peripheral edema. Most
side effects retreat after a few weeks of taking the
medication. Grapefruit and grapefruit juice interfere
with most calcium channel blockers, preventing
them from working properly.
Diuretics
People commonly refer to diuretic medications as
“water pills” because they draw extra fluid from
the body, increasing urination. The purpose is to
reduce the volume of blood, which lowers blood
pressure. Diuretics also help prevent edema (fluid
accumulations in body tissues) such as may occur
with heart failure. Doctors often prescribe diuretics
in combination with other medications. There
are four classifications of diuretic medications,
defined by the drug’s mechanism of action: ALDOS-
TERONE blockers, loop diuretics, potassium-sparing
diuretics, and thiazides.
Aldosterone blockers Aldosterone blockers act
by restricting adrenal gland production of the HOR-
MONE aldosterone, which increases the amount of
sodium the KIDNEYS withdraw from the blood.
They affect the RENIN-angiotensin-aldosterone
(RAA) hormonal system, one of the body’s primary
blood pressure regulatory systems. Though
aldosterone blockers prevent the kidneys from
reabsorbing sodium, they decrease the loss of
potassium so they are also designated as “potassium-sparing.”
However, new understanding
emerged in the early 2000s about other effects
aldosterone has on the heart, particularly following
heart attack and in heart failure and with
respect to the RAA hormonal system, that have
caused doctors to view aldosterone blockers as a
separate category of diuretic.
The two aldosterone blockers available in the
United States are eplerenone (Inspra) and spironolactone
(Aldactone).
Loop diuretics Loop diuretics act on a site
within the glomerular structure of the kidney
called the loop of Henle, which regulates sodium
reabsorption. Loop diuretics cause the kidneys to
pass more sodium, and consequentially more
water, into the urine, and are the most potent of
the diuretic drugs. As the loop of Henle also plays
a role in potassium regulation, loop diuretics also
decrease potassium reabsorption and can result in
potassium depletion. Doctors may also prescribe
potassium supplementation to offset this effect.
The most common side effect of loop diuretics is