Cholestyramine for Diarrhea

Cholestyramine is an oral drug known as a bile acid sequestrant that can be used to treat diarrhea caused by the malabsorption of bile acid (referred to as bile acid diarrhea). Bile acid malabsorption is one of the more common causes of chronic diarrhea associated with conditions like Crohn's disease and medical treatments like cholecystectomy (gallbladder removal).

Cholestyramine is used "off-label" for the treatment of bile acid diarrhea. The drug is officially approved for the treatment of high cholesterol and itching caused by cholestasis (the impaired flow of bile).

This article explains how and when cholestyramine is used to treat chronic diarrhea. It also describes how the drug is taken along with the possible risks and side effects.

What Is Cholestyramine? 

Cholestyramine is a bile acid sequestrant approved by the U.S. Food and Drug Administration (FDA) for the treatment of hypercholesterolemia (high cholesterol) and pruritus (itching) caused by cholestasis.

Cholestyramine works by binding to bile acids and removing them from the body in stools.

Cholesterol is another major component of bile. In people with hypercholesterolemia, the removal of bile from the body forces the liver to produce more bile by using cholesterol in the blood. This helps lower cholesterol levels.

The same mechanism of action can alleviate cholestasis-related itching. Cholestasis is caused by the impaired flow of bile from the liver to the intestines, leading to a buildup of bile acids in the blood. These acids irritate nerves and cause itching. By lowering bile acid levels, itching is relieved.

How Does Cholestyramine Help With Diarrhea?

Cholestyramine is used off-label (meaning for purposes other than those approved by the FDA) to treat diarrhea caused by bile acid malabsorption (BAM).

Under normal circumstances, bile is reabsorbed and returned to the liver after it has broken down dietary fats. But with BAM, bile doesn't get reabsorbed and instead starts to build up in the intestines, causing watery diarrhea.

By removing excess bile, cholestyramine can help ease bile acid diarrhea. However, the drug is not a quick fix and can take several weeks to work depending on the severity of your symptoms.

Other Off-Label Uses

Cholestyramine may also be used off-label to treat Grave's disease. This is an autoimmune disorder that causes an overproduction of thyroid hormones (thyrotoxicosis). Cholestyramine also binds with a compound in the thyroid hormones called iodothyronine and, by doing so, helps remove them from the body.

When Should You Take Cholestyramine?

Some healthcare providers may test a stool sample for high bile acids. Others may prescribe cholestyramine without tests if they suspect BAM is the cause. This is because at least 30% of people diagnosed with functional diarrhea (chronic diarrhea with no known cause) have BAM.

Causes of BAM include:

• Celiac disease
• Chronic pancreatitis
• Crohn's disease
• Diarrhea that persists after a bacterial infection
• Exocrine pancreatic insufficiency
• HIV-associated diarrhea
• Hypertriglyceridemia
• Irritable bowel syndrome (IBS)
• Microscopic colitis

BAM can also affect people who have undergone medical treatments like:

• Chemotherapy
• Cholecystectomy
• Metformin (a drug used to treat high blood sugar)
• Pelvic or abdominal radiation
• Surgical bypass or resection of the ileum (the last section of the small intestine)

Who Should Not Take Cholestyramine?

Cholestyramine should not be taken if you're allergic to the drug or your bile duct is completely blocked (meaning that no bile is being released into your intestines).

Phenylketonuria (PKU) is a genetic disorder characterized by the inability to break down a protein called phenylalanine. Because people with PKU need to avoid phenylalanine—and cholestyramine contains phenylalanine—the drug should not be used as it can be dangerous.

Dosage

Cholestyramine is available as a generic drug and typically comes in a powder form that is mixed into beverages. It is also available as a chewable bar.

When used for diarrhea, cholestyramine is typically prescribed at 4 grams (g) per day. If needed, the dose can be increased to 4 g six times per day.

How to Take It

Cholestyramine is most effective when used as follows:

• Take it before a meal or prior to bedtime.
• Mix the powder with 2 to 6 ounces of non-carbonated fluids, such as water or juice.
• Drink the mixture quickly instead of slowly sipping it.
  
• If you use the chewable bar form, be sure to drink plenty of water.

Your healthcare provider may recommend a daily vitamin supplement while taking cholestyramine as the drug can make it harder to absorb vitamins from food.

Side Effects of Cholestyramine

As with all drugs, cholestyramine can cause side effects. People over age 60 are at highest risk.

Common

Common side effects of cholestyramine include:

• Constipation
• Abdominal discomfort or pain
• Bloating
• Diarrhea
• Gas
• Dizziness
• Headache   
• Skin or tongue irritation
• Easy bleeding due to vitamin K deficiency

Severe

Seek medical help if you experience the following uncommon side effects:

• Severe abdominal pain
• Sudden, significant weight loss
• Vomiting
• Rectal bleeding or black stools
• Severe rash with shortness of breath
• Swelling of the face, throat, or tongue

Warnings and Interactions

Tell your healthcare provider if you're pregnant, breastfeeding, or have a chronic health condition like diabetes, kidney disease, or heart disease. Cholestyramine needs to be used with caution in these groups.

Cholestyramine can affect the absorption of other drugs. Let your healthcare provider know if you take any of the following as the dose may need to be adjusted or a substitute found:

• Birth control pills
• Digoxin
• Hormone therapy
• Penicillin G
• Phenobarbital
• Phenylbutazone
• Phosphate supplements
• Propranolol
• Tetracycline
• Thiazide diuretics
• Thyroid hormones
• Warfarin

Summary

Cholestyramine is a bile acid sequestrant mainly used to treat high cholesterol but it can also be used off-label to treat bile acid diarrhea. The drug is taken by mouth and works by clearing excess bile acid from the body. Many cases of chronic diarrhea are caused by bile acid malabsorption.

Cholestyramine typically comes in powder form and is taken before meals or bedtime. Side effects include constipation, gas, and stomach upset. As cholestyramine can affect the absorption of other drugs, the doses should be separated by one or several hours.