Bile-acid resins and similar agents include:
- The powders cholestyramine (Questran, Questran Light) and
colestipol (Colestid), which you dissolve in liquid
- A chewable bar of cholestyramine (Cholybar)
- The tablet colesevelam (Welchol), which is proving to lower LDL without as many side effects (e.g., constipation)
Bile-acid binding resins work, as their name
suggests, by binding to bile in the digestive tract. This reduces cholesterol in
the following way:
- As part of normal digestion, the liver turns cholesterol into bile acids.
These bile acids move into the intestines, where most of them are
re-absorbed and returned to the liver.
- Bile-acid resin drugs bind to bile acids as they move through the intestines
-- so that the bile acids exit your body with the feces, rather than
re-enter the blood stream.
- In response, the liver converts more cholesterol into bile acids -- and
these, too, are cleared from the body through the feces.
- The result is that LDL ("bad") cholesterol is effectively removed from your
liver and your blood.
When used with dietary control, bile acid resins can reduce LDL levels
by 15-20%. When bile acid resins are combined with nicotinic acid, LDL levels can drop as much as 40-60%.
No medication
Medication
Side effects
Often, people experience constipation, heartburn, gas, and other gastrointestinal problems while taking a drug in this class. These symptoms can become so bothersome that the person wants to change medications.
One study found that only half the standard dose of colestipol was needed when psyllium (Metamucil, Fiberall, Perdiem), a soluble fiber supplement, was added to the drink. In addition, psyllium reduced bloating and constipation. Colesevelam, the newer resin, appears to produce fewer of the gastrointestinal side effects described.
Over time, deficiencies of vitamins A, D, E, K, and B9 (folic acid) may occur, and vitamin supplements may be necessary. If long-term use of bile acid resins leads to depletion of vitamin K in the body, bleeding problems may occur.
Rarely, toxic effects on the liver have been reported. Patients with liver disorders should be monitored.
Drug interactions
Bile-acid binding resins may interfere with other medications, including:
- digoxin (Lanoxin)
- warfarin
- beta-blocker drugs for high blood pressure (such as atenolol, metoprolol, and propranolol)
- diuretics
- sulfonylureas (such as glimepiride and glyburide) use to treat diabetes
In order to prevent drug interactions, medications should be taken one hour before or four to six hours after taking the bile acid-binding resins.
Review Date: August 24, 2004
Reviewed By: Jacqueline A. Hart, M.D., Department of Internal Medicine,
Newton-Wellesley Hospital, Harvard University and Senior Medical Editor,
A.D.A.M., Inc.
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