Bile acid sequestrants act by bonding with bile in the small intestine, preventing its normal reabsorption. The liver must now use body stores of cholesterol to replace the sequestered bile, which is eliminated in the feces. Over time this process lowers the cholesterol level in the blood, especially the LDL form, by as much as 20 percent. Bile acid sequestrants come in powder form and are mixed with water, juice, or soup.
The most common side effects are gastrointestinal, including constipation, bloating, heartburn, and nausea. A high-fiber diet or psyllium supplement at each meal usually relieves these symptoms.
Cholestyramine (Questran, Cholybar) and colestipol (Colestid) may also decrease the absorption of certain vitamins (A, D, E, K, folic acid), minerals (iron and calcium), and drugs (digoxin, acetaminophen, phenobarbital, thiazide diuretics, thyroxin, warfarin). If needed as supplements, these should be taken two to six hours before a meal where a bile sequestration drug is used.
Because they reduce LDL significantly, the bile acid sequestrants are only prescribed for patients known to have a high LDL cholesterol level, known as Type 2 hyperlipidemia. They are not used in hyper-lipidemias due to elevations of other forms of lipids, such as triglycerides. After six weeks of taking bile acid sequestrants, your cholesterol level will be measured again to see if the drug is working. The target LDL level is less than 130 mg/dl if you have other risk factors in addition to elevated cholesterol or less than 100 mg/dl if you have actually already had a heart attack. If a bile sequestrant hasn’t done the job after three months, another kind of cholesterol-lowering drug can be substituted or added.
Probucol (Lorelco), although not strictly a bile acid sequestrant, has similar results to cholestyramine and colestipol, in that it increases the excretion of cholesterol in the bile. It, too, should only be used in Type 2 hyperlipidemia. It persists for many weeks in fatty tissues, and should be stopped at least six months before a planned pregnancy.
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