How do bile acid sequestrants work for lowering cholesterol?

Bile acid sequestrants bind with cholesterol-containing bile acids in the intestines and are then eliminated in the stool. The usual effect of bile acid sequestrants is to lower LDL-cholesterol by about 10 to 20 percent. Small doses of sequestrants can produce useful reductions in LDL-cholesterol. Bile acid sequestrants are sometimes prescribed with a statin for patients with heart disease to increase cholesterol reduction. When these two drugs are combined, their effects are added together to lower LDL-cholesterol by over 40 percent. Cholestyramine, colestipol, and colesevelam are the three main bile acid sequestrants currently available. These drugs are available as powders or tablets. They are not absorbed from the gastrointestinal tract and 30 years of experience with the sequestrants indicate that their long-term use is safe.
Bile acid sequestrant powders must be mixed with water or fruit juice and taken once or twice (rarely three times) daily with meals. Tablets must be taken with large amounts of fluids to avoid gastrointestinal symptoms. Sequestrant therapy may produce a variety of symptoms including constipation, bloating, nausea, and gas.
The bile acid sequestrants are not prescribed as the sole medicine to lower your cholesterol if you have high triglycerides or a history of severe constipation.
Although sequestrants are not absorbed, they may interfere with the absorption of other medicines if taken at the same time. Other medications therefore should be taken at least 1 hour before or 4 to 6 hours after the resin. Talk to your doctor about the best time to take this medicine, especially if you take other medications.
The answer is based on source information from the National Heart, Lung and Blood Institute.
Bile acid sequestrants (resins) work by binding with bile acids in the intestines that contain cholesterol. The cholesterol is then eliminated in the stool. A bile acid sequestrant may be prescribed in combination with another drug if you have high triglycerides or a history of severe constipation. The three main bile acid resins prescribed in the United States are cholestyramine (Questran), colestipol (Colestid) and colesevelam (WelChol).

Bile acid sequestrants come in powders that are mixed with water or fruit juice and usually taken once or twice a day with meals. They are also available in pill form. They should be taken with plenty of water to avoid gastrointestinal side effects, such as constipation, bloating, nausea and gas.

If you take bile acid sequestrants, you should take any other medications at least one hour before or four to six hours after taking a bile acid resin because the bile acids can interfere with the absorption of other medications.
Joseph Saseen, PharmD
Cholesterol Management
In addition to what has been previously described, bile acid sequestrants (also called bile acid resins) cause your body to remove more bad cholesterol (the low-density lipoprotein [LDL] cholesterol) from your circulation. In addition to binding bile acids in your intestines, this increased removal is your body's way of pulling out LDL cholesterol from your circulation so it can be used for other functions such as making needed steroids, cell walls and other essential functions.
Another effect of these drugs is a small but important reduction in blood glucose. If you do not have diabetes, this will not be a problem, but if you do have diabetes or "pre-diabetes" then this is a side benefit that will result in lowering of your blood glucose values, and your A1C (a long term marker of your blood glucose level).
Dean G. Karalis, MD
Cardiology (Cardiovascular Disease)

Bile acid sequestrants are medications that help lower LDL-cholesterol.  These medications come in either pill or powder form and when taken they bind bile acids in the intestine not allowing them to be reabsorbed.  Because our body now has less bile acids being reabsorbed, more need to be made.  Bile acids are produced by using cholesterol.  This increased production of bile acids uses up cholesterol leading to lower levels of LDL-cholesterol in our blood.  The most common side effects of bile acid sequestrants are bloating, diarrhea and other gastrointestinal side effects.  They should be avoided in individuals with elevated triglycerides.  They lower LDL-cholesterol by approximately 15-20%.

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