High blood cholesterol is a major risk factor for heart disease -- the leading cause of death for men and women in the United States. Approximately 102.2 million people in the U.S. have a total cholesterol level greater than 200 mg/dL, a level considered borderline high; and 35.7 million of them suffer from high blood cholesterol, defined as a total cholesterol greater than 240 mg/dL, according to the American Heart Association. The National Cholesterol Education Program urges doctors to educate their patients about the risks of high cholesterol and prescribe appropriate cholesterol lowering drugs as part of their treatment when necessary.
Types of Drugs
Doctors can prescribe one of several types of cholesterol lowering medications. Cholesterol lowering drugs work differently, produce different effects on the various types of cholesterol and cause a different set of side effects. Doctors must assess each patient individually and base their decision on which medication to use on the specific needs of each patient. Doctors most commonly prescribe a statin medication but may also use a bile acid sequestrant, ezetimibe, nicotinic acid or a fibric acid derivative.
Mechanism of Action
The total amount of cholesterol in your blood comes from two sources: internal production in the liver cells and dietary cholesterol in the food you eat. The body produces approximately 75 percent of your total cholesterol. The class of medications known as statins, also called HMG CoA reductase inhibitors, inhibits the activity of an enzyme, HMG CoA reductase, needed for the liver cells to produce cholesterol. By slowing the production of cholesterol, the body can use the cholesterol in the blood, therefore reducing cholesterol levels. Bile acid sequestrants bind to bile acid -- a substance produced in the liver to aid in the digestions of fats. The liver uses cholesterol to produce bile acids. When the drug binds to bile acids, it prompts the liver to produce more bile acids, which uses more cholesterol. Ezetimibe inhibits the absorption of dietary cholesterol in the intestines. Fibric acid derivatives start a chain of chemical reactions in the body that results in a decreased production of very low-density lipoprotein, or VLDL, and triglycerides which can affect overall cholesterol levels. The exact mechanism of action of nicotinic acid, known as vitamin B3, remains unknown but it has proven to help reduce cholesterol levels.
Cholesterol Affected
Since elevated levels of low-density lipoprotein -- LDL, referred to as the "bad" cholesterol, is the major cause of coronary heart disease, doctors center their treatments on lowering LDL levels. High-density lipoprotein, or HDL, helps to remove cholesterol from the body; an increased risk of heart disease occurs if the levels of HDL in your body are too low. Statin medications lower LDL levels between 18 and 55 percent and stimulate an increase in HDL levels by 5 to 15 percent. Bile acid sequestrants decrease LDL levels between 15 and 30 percent and increase HDL levels 3 to 5 percent. Nicotinic acid produces a more mild effect on LDL levels, only decreasing them by 5 to 25 percent. Nevertheless, nicotinic acid increases HDL levels 15 to 35 percent. Fibric acid drugs also produce lower LDL results, lowering it 5 to 20 percent but they can increase HDL levels by 10 to 20 percent. Ezetimibe blocks cholesterol absorption up to 50 percent, according to "Current Cardiology Reports." When taken with a statin medication, ezetimibe can lower LDL levels by an additional 15 to 20 percent, Mayo Clinic states.
Side Effects
Most medications produce some type of effect on the body in addition to the desired therapeutic effect. Statins produce few immediate and short-term side effects, but they can cause nausea, diarrhea or constipation. The most troubling effects are the long-term effects of liver damage and muscle problems that begin with muscle pain and tenderness, but can escalate to rhabdomyolosis -- the breakdown of muscle cells and release of protein in the blood. Bile acid sequestrants don't seem to produce serious side effects but gastrointestinal disturbances including abdominal pain, bloating, constipation and nausea can become troublesome. Nicotinic acid causes blood vessels to dilate, which causes the side effects of flushing and hot flashes. Patients who take fibric acid derivatives may experience some gastrointestinal disturbances but those taking blood thinning medications should consult their doctor as these medications can enhance their effects.
References
- American Heart Association: Cholesterol Statistics
- "Current Cardiology Reports": Ezetimibe -- A Novel Cholesterol-Lowering Agent; Shailendra B. Patel; November 2004
- Mayo Clinic: Statins -- Are These Cholesterol Lowering Drugs Right for You?; February 2010
- National Heart Lung and Blood Institute: Cholesterol Education Program; May 2001
