Cholestyramine

Cholestyramine or colestyramine (Questran®, Questran Light®, Cholybar®) is a bile acid sequestrant, which binds bile in the gastrointestinal tract to prevent its reabsorption. The resin is a strong anion exchange resin, which means that 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 feces. When bile acids are excreted, plasma cholesterol is converted to bile acid to normalize bile acid levels. This conversion of cholesterol into bile acids lowers plasma cholesterol concentrations. Bile acid sequestrants such as cholestyramine are primarily used to treat hypercholesterolemia, but can also be used to treat the pruritus, or itching, that often occurs during liver failure due to the liver's inability to eliminate bile.

Cholestyramine is also used in patients who have undergone post ileal (part of the small bowel) resection in Crohn's disease to prevent diarrhoea. This is due to the fact that the terminal ileum is where the bile acids are reabsorbed. So when this is resected the bile acids pass into the large bowel and pull water into the bowel due to their osmotic effect thereby causing diarrhoea. Cholestyramine prevents this by making them insoluble and therefore not osmotically active.

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Available forms

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

Dosage

4 to 8 grams once or twice daily, maximum dose 24 grams a day.

Side-effects

The following side effects have been noted.[1]

• Most frequent: Constipation
• Seldom: tooth discoloration; tooth enamel erosion; premature tooth decay; all from prolonged oral exposure of the suspension.

Warnings

Patients with hypothyroidism, diabetes, nephrotic syndrome, dysproteinemia, obstructive liver disease, kidney disease, or alcoholism, should consult their doctor before taking this medication.[2] 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

The following interactions have been noted.[3]

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

Most interactions are due to risk of decreased absorption of these drugs since Cholestyramine will prevent full absorption.

Duration of treatment

The duration of treatment is not limited, but the prescribing physician should reassess in regular intervals, if continued treatment is still necessary.

Overdose

Principal overdose risk is blockage of intestine or stomach.

Other remarks

Cholestyramine may interfere in the absorption of fat soluble vitamins such as Vitamins A, D, E, and K. There are no special considerations regarding alcohol consumption. [4]

References