Statins

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What are statins, and how do they work?

"Statins" is a class of drugs that lowers the level of cholesterol in the blood by reducing the production of cholesterol by the liver. (The other source of cholesterol in the blood is dietary cholesterol.) 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). 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 arteries. These plaques block the arteries and reduce the flow of blood to the tissues 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 reduced flow is caused by plaques in the arteries of the brain, the result is a stroke. If reduced flow is caused by plaques in the arteries of the leg, they 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 may also stabilize plaques and make them less prone to rupturing and develop clots.

The important role of cholesterol in atherosclerosis is widely accepted by scientists. Research from the last few years shows that aggressive cholesterol reduction is more beneficial than modest reductions.

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. In addition to lowering cholesterol levels, statins also 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 reduction of cholesterol 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 angiotensin converting enzyme inhbitors (ACE inhibitors), are an important class of drugs because they have been shown to reduce the incidence of heart attacks, strokes, and death.




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