Statins
Pharmacy Author:
Omudhome
Ogbru, Pharm.D.
Medical Editor:
Jay Marks, MD
What
are statins, and how do they work?
"Statins" are a
class of drugs that lowers the level of cholesterol in the blood by reducing the
production of cholesterol by the liver. Statins
block the enzyme in the liver that is responsible for making cholesterol. This
enzyme is called hydroxy-methylglutaryl-coenzyme A reductase (HMG-CoA reductase
for short). Scientifically, statins are referred to as HMG-CoA reductase inhibitors.
Cholesterol is critical to
the normal function of every cell in the body. However, it also contributes to
the development of atherosclerosis, a condition in which cholesterol-containing
plaques form within the arteries. These plaques block the arteries
and reduce the flow of blood to the tissues that the arteries supply. When
plaques rupture, a blood clot forms on the plaque, thereby further blocking the
artery and reducing the flow of blood. When blood flow is reduced sufficiently
in the arteries that supply blood to the heart, the result is angina (chest
pain) or a heart attack. If the clot occurs on plaques in the brain, the result
is a stroke. Plaques and clots occurring on
plaques in the leg cause intermittent claudication (pain in the legs
while walking). By reducing
the production of cholesterol, statins are able to slow the formation of new
plaques and occasionally can reduce the size of plaques that already exist. In
addition, through mechanisms that are not well understood, statins also
stabilize plaques and make them less prone to rupturing and forming clots.
Although the important
role of cholesterol in atherosclerosis is widely accepted by scientists,
research also shows that atherosclerosis is a complex process that involves more
than just cholesterol. For example, scientists have discovered that inflammation
in the walls of the arteries may be an important factor in atherosclerosis. New
research shows that statins reduce inflammation, which could be another
mechanism by which statins beneficially affect atherosclerosis.
This reduction of inflammation does not depend on statins' ability to
reduce cholesterol. Furthermore, these anti-inflammatory effects can be seen as
early as two weeks after starting statins.
For
what conditions are statins used?
Statins are used for
preventing and treating atherosclerosis that causes chest pain, heart attacks,
strokes, and intermittent claudication in individuals who have or are at risk
for atherosclerosis. Risk factors for atherosclerosis include abnormally
elevated cholesterol levels, a family history of heart attacks (particularly at
a young age), increasing age, and diabetes. Most individuals are placed on
statins because of high levels of cholesterol. Though cholesterol reduction is
important, heart disease is complex and, as discussed previously, other factors
such as inflammation may play a role. Thirty-five percent of individuals who
develop heart attacks do not have high blood cholesterol levels, yet most of
them have atherosclerosis. This
means that high levels of cholesterol are not always necessary for
atherosclerotic plaques to form.
Because it is not clear
which effect of statins is responsible for their benefits, the goal of treatment
with statins should not be only the reduction of cholesterol to normal levels,
but rather the prevention of the complications of atherosclerosis-angina,
heart attacks, stroke, intermittent claudication, and death. This concept is
important because it allows for individuals who have or are at risk for
atherosclerosis, but do not have high levels of cholesterol, to be considered
for treatment with statins. Statins, like ACE inhibitors , are an
important class of drugs because these drugs have been shown to reduce the incidence of
heart attacks, strokes, and death.
Are
there differences among statins?
Statins differ in several ways. The most obvious difference
is in their ability to reduce cholesterol. Currently, atorvastatin (Lipitor) and
rosuvastatin (Crestor) are the most potent, and fluvastatin (Lescol) is the
least potent. The statins also
differ in how strongly they interact with other drugs. Specifically,
pravastatin and rosuvastatin levels in the body are less likely to be elevated
by other drugs that may be taken at the same time as the statins.
This is so because the enzymes in the liver that eliminate pravastatin
and rosuvastatin are not blocked by many of the drugs that block the enzymes
that eliminate other statins. This prevents the levels of pravastatin and
rosuvastatin from rising and leading to increased toxicity such as myopathy,
inflammation of the muscles. For example, in scientific studies,
patients who took both verapamil and simvastatin experienced myopathy
10 times more often than patients who received simvastatin alone because
verapamil increased the blood levels of simvastatin.
Statins differ in the frequency with which they cause a
severe type of myopathy called rhabdomyolysis, in which muscles are severely
damaged. Cerivastatin (Baycol) was withdrawn from pharmacies worldwide because
it caused rhabdomyolysis 10 to 100 times more often than other statins.
Rhabdomyolysis may occur more often in patients taking lovastatin, simvastatin
or atorvastatin than patients taking pravastatin or fluvastatin.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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