It is a sequestrant of bile acids that binds to the bile in the gastrointestinal tract to prevent reabsorption.
Cholestyramine (INN), whose trade names are Questran, Questran Light, Cholybar, and Olestyr, is a strong ion exchange resin. It can exchange chloride anions with anionic bile acids in the gastrointestinal tract and bind them firmly in the resin matrix.
The functional group of the anion exchange resin is a quaternary ammonium group bonded to an inert styrene-divinylbenzene copolymer.
Cholestyramine eliminates bile acids from the body by forming insoluble complexes with bile acids in the intestine, then excreted in the stool.
As a result of this loss of bile acids, more plasma cholesterol is converted into bile acids in the liver to normalize levels. This conversion of cholesterol into bile acids reduces plasma cholesterol levels.
Medical uses of cholestyramine
Bile acid sequestrants such as cholestyramine were used for the first time to treat hypercholesterolemia, but since the introduction of statins, they now have only a minor role in this indication.
Cholestyramine is commonly used to treat diarrhea caused by bile acid malabsorption. It was first used in patients with Crohn’s disease who had undergone ileal resection.
The terminal portion of the small intestine (ileum) is where the bile acids are reabsorbed. When this section is eliminated, the bile acids pass into the large intestine and cause diarrhea due to the stimulation of the secretion of chlorides/fluids by the colonocytes, which produces secretory diarrhea.
Cholestyramine prevents this increase in water by making the bile acids insoluble and osmotically inactive. Cholestyramine is also used to control other types of bile acid diarrhea.
The primary idiopathic form of biliary diarrhea is a common cause of chronic functional diarrhea, often misdiagnosed as irritable bowel syndrome with a predominance of diarrhea (IBS-D). Most of these patients respond to cholestyramine.
It is beneficial in the treatment of post-cholecystectomy syndrome with chronic diarrhea. Cholestyramine is also helpful in the treatment of post-vagotomy diarrhea.
Cholestyramine may be helpful in the treatment of Clostridium difficile infections, absorb toxins A and B, and reduce diarrhea and the other symptoms that cause these toxins. However, because it is not an anti-infective, it is used in concert with vancomycin.
It is also used in the procedure of “washing” in patients taking leflunomide or teriflunomide to help eliminate the drug in the case of drug discontinuation due to serious side effects caused by leflunomide or teriflunomide.
A case report suggests that cholestyramine may be helpful for cyanobacterial poisoning (microcystin) in dogs.
Ointments containing cholestyramine compounds with Aquaphor have been used in the topical treatment of diaper rash in infants and young children.
Cholestyramine also binds with oxalate in the gastrointestinal tract, ultimately reducing the formation of calcium oxalate and oxalate stones.
Available forms of cholestyramine
Cholestyramine is available in powder form, 4 g packs, or larger containers. In the United States, it can be purchased as a generic medicine or as Questran or Questran Light (Bristol-Myers Squibb).
A typical dose is 4 to 8 g once or twice a day, with a maximum of 24g / d.
Side effects of cholestyramine
These side effects have been noted: constipation and increased plasma triglycerides.
Intestinal obstruction has been reported in patients with previous bowel surgery who should use cholestyramine with caution. Hyperchloremic metabolic acidosis induced by cholestyramine has also been reported infrequently.
Other medications must be taken at least one hour before or four to six hours after cholestyramine to reduce possible interference with absorption.
Patients with phenylketonuria should consult a doctor before taking Questran Light because that product contains phenylalanine.
Interactions with other medications
Interactions with these medications have been observed:
- Digitalis purpurea.
- Estrogens and progestins.
- Oral drugs for diabetes.
- Penicillin G.
- Diuretic pills type thiazide .
- Thyroid medicine
The majority of interactions are due to the risk of less absorption of these medications.
The duration of treatment is not limited, but the prescribing physician must re-evaluate at regular intervals if continued treatment is necessary. The main risk of overdose is blockage of the intestine or stomach.