Cholestyramin

Cholestyramine is a bile acid sequestrant used to reduce elevated low-density lipoprotein (LDL) cholesterol and to treat certain bile-acid–related conditions. It is not absorbed into the bloodstream; instead, it binds bile acids in the gastrointestinal tract and is excreted in feces.

Mechanism of action

Cholestyramine forms an insoluble complex with bile acids in the small intestine. This increases bile-acid excretion and lowers hepatic cholesterol pools, which in turn stimulates the liver to convert more cholesterol into bile acids, reducing circulating LDL cholesterol.

Medical uses

The medication is indicated for primary hypercholesterolemia and as an adjunct in familial hypercholesterolemia. It is also used to treat pruritus associated with partial biliary obstruction or cholestasis and to manage diarrhea due to bile-acid malabsorption.

Administration and dosage

Cholestyramine is typically taken orally as powder or tablets, often mixed with water, juice, or applesauce. Starting doses commonly fall around 4 g once or twice daily, titrating as needed and tolerated, with a usual maximum of up to about 24 g per day in divided doses. It should be taken with meals to improve tolerability.

Safety and interactions

Because cholestyramine binds other substances in the gut, it can interfere with the absorption of fat-soluble vitamins (A, D, E, K) and various medications. Other drugs should be taken at least 1 hour before or 4–6 hours after cholestyramine. It is contraindicated in complete biliary obstruction and used with caution in individuals with markedly elevated triglycerides; long-term use requires monitoring for deficiencies and interactions.

Side effects

Common adverse effects are gastrointestinal in nature, including constipation, bloating, and abdominal discomfort. Fecal changes (e.g., lighter or bulkier stools) and, rarely, fecal impaction may occur.