Cholestyramine

Cholestyramine

Clinical data
Trade names	Questran
AHFS/Drugs.com	monograph
MedlinePlus	a682672
Pregnancy category	US: C (Risk not ruled out) C
Legal status	US: ℞-only ℞ (Prescription only)
Routes of administration	oral
Pharmacokinetic data
Bioavailability	low
Protein binding	unknown
Metabolism	bile acids
Biological half-life	1 hour
Excretion	feces
Identifiers
CAS Number	11041-12-6 Y
ATC code	C10AC01
DrugBank	DB01432 Y
ChemSpider	none
UNII	4B33BGI082 N
KEGG	D02690 Y
ChEMBL	CHEMBL1201625 N
Chemical data
Molar mass	In average, exceeds 1×106 g/mol
NY (what is this?)  (verify)

Colestyramine (INN) or cholestyramine (USAN) (trade names Questran, Questran Light, Cholybar, Olestyr) is a bile acid sequestrant, which binds bile in the gastrointestinal tract to prevent its reabsorption. It is a strong ion exchange resin, which means it can exchange its chloride anions with anionic bile acids in the gastrointestinal tract and bind them strongly in the resin matrix. The functional group of the anion exchange resin is a quaternary ammonium group attached to an inert styrene-divinylbenzene copolymer.

Cholestyramine removes bile acids from the body by forming insoluble complexes with bile acids in the intestine, which are then excreted in the feces. As a result of this loss of bile acids, more plasma cholesterol is converted to bile acids in the liver to normalize levels. This conversion of cholesterol into bile acids lowers plasma cholesterol levels.

Medical uses

Bile acid sequestrants such as cholestyramine were first used to treat hypercholesterolemia, but since the introduction of statins, now have only a minor role for this indication. They can also be used to treat the pruritus, or itching, that often occurs during liver failure and other types of cholestasis where the ability to eliminate bile acids is reduced.

Cholestyramine is commonly used to treat diarrhea resulting from bile acid malabsorption.^[1] It was first used for this in Crohn's disease patients who had undergone ileal resection.^[2] The terminal portion of the small bowel (ileum) is where bile acids are reabsorbed. When this section is removed, the bile acids pass into the large bowel and cause diarrhea due to stimulation of chloride/fluid secretion by the colonocytes resulting in a secretory diarrhea. Cholestyramine prevents this increase in water by making the bile acids insoluble and osmotically inactive.

Cholestyramine is also used in the control of other types of bile acid diarrhea. The primary, idiopathic form of bile acid diarrhea is a common cause of chronic functional diarrhea, often misdiagnosed as diarrhea-predominant irritable bowel syndrome (IBS-D), and most of these patients respond to cholestyramine.^[3] It is beneficial in the treatment of postcholecystectomy syndrome chronic diarrhea.^[4][5] Cholestyramine is also useful in treating Post-vagotomy diarrhea.^[6][7]

Cholestyramine can be helpful in the treatment of Clostridium difficile infections, to adsorb toxins A and B, and reduce the diarrhea and the other symptoms these toxins cause. However, because it is not an anti-infective, it is used in concert with vancomycin.^[8]

It is also used in the "wash out" procedure in patients taking leflunomide or teriflunomide to aid drug elimination in the case of drug discontinuation due to severe side effects caused by leflunomide or teriflunomide.^[9]

A case report suggests that Cholestyramine may be useful for cyanobacterial (microcystin) poisoning in dogs.^[10]

Ointments containing cholestyramine compounded with aquaphor have been used in topical treatment of diaper rash in infants and toddlers.^[11]

Available forms

Cholestyramine is available as powder form, in 4-g packets, or in larger canisters. In the United States, it can be purchased either as a generic medicine, or as Questran or Questran Light (Bristol-Myers Squibb).

Dosage

A typical dose is 4 to 8 g once or twice daily, with a maximum dose of 24 g/d.

Side effects

These side effects have been noted:^[12]

• Most frequent: constipation
• Increased plasma triglycerides^[13]

Intestinal obstruction has been reported in patients with previous bowel surgery who should use cholestyramine cautiously.^{[14] [15]}

Patients with hypothyroidism, diabetes, nephrotic syndrome, dysproteinemia, obstructive liver disease, kidney disease, or alcoholism should consult their doctor before taking this medication.^[12] Other drugs should 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 with a physician before taking Questran Light because that product contains phenylalanine.

Drug interactions

Interactions with these drugs have been noted:^[12]

• Digitalis
• Estrogens and progestins
• Oral diabetes drugs
• Penicillin G
• Phenobarbital
• Spironolactone
• Tetracycline
• Thiazide-type diuretic pills
• Thyroid medication
• Warfarin
• Leflunomide

Most interactions are due to the risk of decreased absorption of these drugs.^[15] The duration of treatment is not limited, but the prescribing physician should reassess at regular intervals if continued treatment is still necessary. The principal overdose risk is blockage of intestine or stomach.

Cholestyramine may interfere in the absorption of fat-soluble vitamins such as vitamins A, D, E, and K. No special considerations regarding alcohol consumption are made.^[12]

Notes and references

• The Merck Index (12 ed.). p. 2257. 

External links

• U.S. National Library of Medicine: Drug Information Portal - Cholestyramine