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Cholestyramine (CSM) Uses & Side Effects

Written by Puya Yazdi, MD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
Jonathan Ritter
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology) | Written by Puya Yazdi, MD | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Cholestyramine (CSM) is a bile acid sequestrant used to lower cholesterol and to relieve itching associated with liver disease. Its other uses remain unproven. Read this post to learn about its evidence-based uses and side effects.

Disclaimer: Cholestyramine is available only with your doctor’s prescription. The aim of this post is to outline the scientific findings related to cholestyramine for purely informational purposes. Please discuss your medications with your doctor.

What is Cholestyramine?


Cholestyramine is an oral medication used as add-on therapy to lower high cholesterol, along with diet and lifestyle changes. It is also used to reduce itching in people with blocked bile ducts (primary biliary obstruction), a type of liver disease.

These are the only proven, safe, and well-researched uses of cholestyramine.

Nonetheless, some doctors prescribe this drug off-label for Chronic Inflammatory Response Syndrome (CIRS) and other “biotoxin-related illness.” This practice is not evidence-based and its safety is unknown.

Additionally, most doctors do not accept that there is any causal connection between mold exposure and any health issue. In light of this, mold illness and CIRS are considered to be highly controversial, pseudo diagnoses. Similarly, what people subjectively describe as CIRS has been linked to psychological disorders [1, 2, 3, 4].

Mechanism of Action

Cholestyramine (CSM) is a bile acid sequestrant. It binds to bile acids in the intestine, which prevents them from being reabsorbed into the body. Thus, the body eliminates more bile acids, along with cholestyramine, with the stool. To compensate, the liver turns more cholesterol to bile acids, which lowers cholesterol levels in the blood.

Uses of Cholestyramine

Effective for:

The only indications for cholestyramine are as an add-on therapy in people with high cholesterol and for the relief of itching due to certain forms of liver disease (partial biliary obstruction).

Consult your doctor about any medication-related questions you may have as well as to learn more about how to properly use cholestyramine for these indications.

1) Lowering High Blood Cholesterol

Cholestyramine is used as an add-on therapy to lower high cholesterol levels in the blood. Lowering cholesterol helps decrease the risk of strokes and heart attacks.

It should be prescribed in addition to an adequate diet (e.g. low in cholesterol and saturated fats) and lifestyle changes aimed at maintaining healthy cholesterol levels. Some healthy lifestyle changes include exercising, losing weight if overweight, and stopping smoking.

2) Itching due to Liver Disease

People with liver and biliary disease often experience itching. This symptom is thought to be a result of the accumulation of bile acids in the skin due to the inability of the liver or bile ducts to remove bile acids as well as they should [5].

By binding to bile acids in the intestines, cholestyramine prevents their absorption and lowers their blood levels. This provides symptomatic relief for people with itching due to bile and liver disease.

Additionally, one paper suggested that cholestyramine ointments might reduce diaper rashes in babies, but large-scale trials are lacking to back up its use for this purpose [6].

Likely Effective for:

3) Chronic Diarrhea due to Bile acid malabsorption

Bile acid malabsorption (BAM) is a relatively common cause of chronic diarrhea. According to some estimates, about one in every 20 people in the general population suffers from BAM [7].

On the other hand, BAM is much more common in people with Crohn’s disease and diarrhea-predominant irritable bowel syndrome [7].

Certain stool analyses can help doctors determine a patient’s level of bile acid production and whether they would benefit from cholestyramine. According to some evidence, a trial of cholestyramine is a less time-consuming and expensive practice [7].

An estimated 70% to 96% of chronic diarrhea patients with BAM respond to short-course cholestyramine [7].

4) Some Forms of Drug Overdose

Cholestyramine binds some drugs in the intestine, which prevents their absorption and speeds up their elimination. It is sometimes used in cases of drug overdose.

For example, digoxin is a drug used to treat heart failure. Toxic levels of digoxin can cause serious health problems, and cholestyramine will reduce levels and decrease the side effects of digoxin [8].

Nonetheless, more specific antidotes have been developed for various types of drug overdose.

Possibly Effective for:

5) Infectious Diarrhea

Clostridium difficile (C. diff) infections are a major cause of infectious diarrhea in hospitals. The typical treatment for more severe cases involves the antibiotics vancomycin and metronidazole. Unfortunately, one in five patients relapses after the antibiotics are continued. A small number continue relapsing after several antibiotic courses [9].

One study suggests that adding cholestyramine or Saccharomyces boulardii to longer vancomycin treatment in these multiple-relapse patients may be beneficial. But large trials are needed to confirm the effectiveness of this combination [9].

Insufficient Evidence for:

The following off-label uses are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of cholestyramine for any of the below listed uses.

Post-Surgery Hemorrhoids Pain

In patients post-surgery (for patients with hemorrhoids), cholestyramine ointments helped reduce pain by 15%. The patients also took fewer painkillers. Additional trials are needed to determine the effectiveness and safety of cholestyramine ointment for reducing pain after hemorrhoids surgery [10].

Colon Inflammation

In one trial, cholestyramine added to mesalazine (an NSAID) treatment reduced symptoms of collagenous colitis, a type of chronic inflammatory disease of the colon. Large-scale trials are needed [11].

Spur Cell Anemia

According to limited evidence, cholestyramine coupled with flunarizine (a calcium antagonist, not available in the US) and pentoxifylline (a vasodilator and anti-inflammatory) may help treat spur cell anemia, which is a lack of red blood cells due to alcoholism [12].

This combined treatment helped patients recover from anemia and reduced the number of spur cells in the body in one trial. Further research is needed before we can draw any conclusions about this potential use [12].

Blocked Gallbladder

Gallbladder stasis or blocked gallbladder is frequent in people who are obese, and it may contribute to their increased risk for gallstones. Some studies suggest that cholestyramine increases emptying of the gallbladder, which might prevent gallstones in overweight people. Additional studies are warranted [13].

Blood Sugar Control in Diabetes Patients

Cholestyramine reduced blood glucose levels in one trial of patients with type 2 diabetes. Proper large-scale clinical trials are lacking [14].


Limited evidence suggests that cholestyramine may reduce some symptoms of hyperthyroidism, but safety and efficacy data are lacking [15].

Side Effects & Safety of Cholestyramine

Side Effects

This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.

Call your doctor for medical advice about side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.

The following side effects of cholestyramine have been reported:

Mix each 9 g dose of cholestyramine for oral suspension with 2 to 6 ounces of water. Make sure to drink enough fluids when taking this medication and aim to maintain good oral hygiene.

Limited evidence suggests that cholestyramine may lower the levels of Vitamin D and K. In some cases, patients were Vitamin K deficient after long-term usage of cholestyramine [17, 18].

In rats, cholestyramine reduced Magnesium, Iron, and Zinc levels. These effects have not been reported in humans [19].

Consult your doctor if you are concerned about nutrient deficiency and are considering vitamin, mineral, or any other supplements.

In one study on healthy adults, a daily dose of 8 g of cholestyramine slightly increased levels of alanine aminotransferase, a marker of liver damage. However, these elevations were considered to be benign and clinically irrelevant. Additional large-scale safety studies focusing on markers of liver health might be warranted [20].


Contraindicated for severe hypertriglyceridemia and complete biliary obstruction [21].

Drug Interactions

Cholestyramine may delay or decrease the absorption of the following drugs [22]:

  • Digoxin [8]
  • Diclofenac [23]
  • Warfarin [24]
  • Propranolol [25]
  • Thyroid and thyroxine preparations [25]
  • Estrogens and progestins (including birth control pills) [25]
  • Hydrochlorothiazide [26]
  • Leflunomide [27]
  • Cerivastatin [28]
  • Glipizide [29]
  • Troglitazone [30]

About the Author

Puya Yazdi

Puya Yazdi

Dr. Puya Yazdi is a physician-scientist with 14+ years of experience in clinical medicine, life sciences, biotechnology, and nutraceuticals.
As a physician-scientist with expertise in genomics, biotechnology, and nutraceuticals, he has made it his mission to bring precision medicine to the bedside and help transform healthcare in the 21st century. He received his undergraduate education at the University of California at Irvine, a Medical Doctorate from the University of Southern California, and was a Resident Physician at Stanford University. He then proceeded to serve as a Clinical Fellow of The California Institute of Regenerative Medicine at The University of California at Irvine, where he conducted research of stem cells, epigenetics, and genomics. He was also a Medical Director for Cyvex Nutrition before serving as president of Systomic Health, a biotechnology consulting agency, where he served as an expert on genomics and other high-throughput technologies. His previous clients include Allergan, Caladrius Biosciences, and Omega Protein. He has a history of peer-reviewed publications, intellectual property discoveries (patents, etc.), clinical trial design, and a thorough knowledge of the regulatory landscape in biotechnology. He is leading our entire scientific and medical team in order to ensure accuracy and scientific validity of our content and products.

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