Cholestyramine

Introduction Overview

Generic Name

cholestyramine

Brand Name

Questran

Dosage Form

Oral powder for suspension

Drug Class

Bile acid sequestrants

Pharmacokinetics

Absorption:
Cholestyramine is a non-absorbable anion-exchange resin that acts locally in the gastrointestinal tract and is not systemically absorbed. Due to its polymeric resin nature, it remains confined to the lumen of the gastrointestinal tract. This property minimizes systemic exposure and reduces systemic side effects, making it suitable for long-term use for hyperlipidemia and pruritus associated with bile duct obstruction. Studies indicate that following oral administration, cholestyramine binds bile acids within the intestinal lumen, preventing their reabsorption, thus interrupting the enterohepatic circulation of bile acids without measurable systemic levels.

Distribution:
As cholestyramine is not absorbed into the bloodstream, it does not distribute to tissues or organs. Its action remains confined to the gastrointestinal tract where it binds bile acids. This lack of systemic absorption eliminates concerns about tissue accumulation, systemic toxicity, or interactions outside the gut lumen. Its confinement in the gastrointestinal lumen also means it does not cross biological membranes such as the intestinal epithelium or blood-brain barrier.

Metabolism:
Cholestyramine itself is not metabolized by the body given its nonabsorbable polymeric structure. It acts solely as a resin that physically binds bile acids. The resin is chemically stable and undergoes no enzymatic degradation or metabolic transformation by hepatic enzymes or intestinal flora. Bile acids bound to cholestyramine are rendered insoluble and are subsequently excreted with the feces.

Elimination:
The elimination of cholestyramine occurs through fecal excretion as the resin-bound bile acids are not reabsorbed from the intestines. The drug-bile acid complex is eliminated intact, without metabolic alteration. This fecal elimination results in the interruption of the normal enterohepatic recycling of bile acids, causing increased hepatic conversion of cholesterol to bile acids to replenish the bile acid pool. This effect ultimately lowers serum cholesterol levels by upregulating LDL receptors and increasing LDL clearance from blood. The polymer is excreted via the gastrointestinal tract and does not undergo renal or hepatic clearance.

Dosage Forms

Available Dosage Forms:
Questran is supplied as a powder for oral suspension. The powder is usually provided in packets or bulk containers to be mixed with water or other suitable non-carbonated liquids prior to ingestion.

Dosages for Adults and Adolescents:
Cholestyramine (Questran) is typically initiated at doses ranging from 4 grams once or twice daily. Doses can be adjusted according to cholesterol levels, tolerability, and clinical response, with common dosages up to 24 grams daily divided into multiple doses. The frequency of administration may range from once up to six times daily depending on the indication and physician instructions. Patients are advised to mix powders thoroughly with 2 to 6 ounces of water, broth, or suitable food (applesauce or crushed pineapple) for easier administration.

Specific Patient Populations:
For patients with biliary obstruction-associated pruritus, similar dosing regimens apply with careful monitoring of clinical response and gastrointestinal tolerance. For elderly patients, monitoring for increased risk of constipation is important. Patients with phenylketonuria (PKU) should be cautioned, as formulations may contain phenylalanine. Pregnant and breastfeeding women should only use under careful medical supervision with potential vitamin supplementation.

Additional Notes:
The Questran brand has been discontinued in the U.S., but generic versions of cholestyramine powder remain available. Careful adherence to dosing instructions is vital due to possible side effects such as constipation and interference with absorption of other medications and vitamins.

Mechanism Of Action

Cholestyramine (Questran) is a bile acid sequestrant that lowers cholesterol primarily by binding bile acids in the intestinal lumen. Its quaternary ammonium polymer structure carries a strong positive charge that electrostatically binds the negatively charged bile acids. By sequestering bile acids, cholestyramine prevents their reabsorption in the ileum, interrupting the enterohepatic circulation.

This interruption results in increased hepatic conversion of cholesterol to bile acids to make up for the loss, upregulating the expression of hepatic LDL receptors. The enhanced receptor activity increases uptake and clearance of LDL cholesterol from the bloodstream, leading to decreased plasma LDL cholesterol levels. This results in a notable reduction in serum cholesterol, especially LDL cholesterol, which plays a central role in atherosclerotic cardiovascular disease.

Additionally, by decreasing bile acid reabsorption, cholestyramine reduces pruritogenic substances responsible for itching associated with partial biliary obstruction and cholestasis. The sequestration reduces circulating bile acid levels contributing to symptomatic relief of pruritus.

Clinically, cholestyramine's unique non-absorbable resin mechanism differentiates it from systemic lipid-lowering agents such as statins. It is often used in combination with them to achieve greater cholesterol reduction. Research demonstrates the efficacy of cholestyramine in improving lipid profiles and managing pruritus secondary to cholestatic liver diseases. Despite its efficacy, its capacity to bind other anionic drugs and fat-soluble vitamins necessitates careful timing of administration and supplementation to mitigate interactions and deficiencies.

Pharmacological Actions

Binds bile acids in the intestine, preventing their reabsorption.
Interrupts enterohepatic circulation of bile acids.
Increases hepatic conversion of cholesterol to bile acids.
Upregulates hepatic LDL receptor expression, enhancing LDL clearance.
Lowers serum LDL cholesterol concentrations.
Reduces pruritogenic circulating bile acids in biliary obstruction.
Acts locally in the gastrointestinal tract without systemic absorption.
May bind other negatively charged drugs, affecting their absorption.
Alters enterohepatic cycling potentially increasing hepatic cholesterol catabolism.
May cause mild gastrointestinal motility changes due to resin polymerization.
Acts as an adjuvant in lipid-lowering therapy alongside statins and diet.
Facilitates excretion of bile acid-bound cholesterol in feces.
Does not inhibit cholesterol synthesis directly but enhances cholesterol catabolism.
May decrease absorption of fat-soluble vitamins (A, D, E, K).
Exerts therapeutic effects on pruritus through reduction of bile acid levels.

Therapeutic Or Clinical Uses

Treatment of hyperlipoproteinemia, particularly type IIa with elevated LDL cholesterol.
Adjunct therapy for lowering serum cholesterol in patients intolerant or resistant to statins.
Management of pruritus (itching) caused by partial biliary obstruction or cholestasis.
Used in combination with diet and lifestyle modifications to reduce coronary artery disease risk.
Treatment of hyperlipidemia where bile acid binding can enhance LDL clearance.
Symptomatic relief for patients with cholestatic liver disease-related itching.
Adjunct therapy in familial hypercholesterolemia to aid cholesterol reduction.
Management of diarrhea associated with bile acid malabsorption (off-label use).
Therapeutic option in patients contraindicated for other lipid-lowering drugs.
Useful in post-bariatric surgery patients to reduce bile acid-related side effects.
May serve as a binding agent in certain toxic ingestions by adsorbing bile acid-bound toxins (investigational).
Treatment of hyperlipoproteinemia type IIb as part of combination regimens.
Use in patients with excessive LDL despite diet and lifestyle control.
Reduction of LDL cholesterol to decrease risk of cardiovascular events in high-risk populations.
Potential therapy in pediatric patients with familial hypercholesterolemia under specialist supervision.

Side Or Adverse Effects

Mild to moderate constipation is the most common adverse effect.
Gastrointestinal discomfort, such as bloating, flatulence, and abdominal pain.
Nausea and loss of appetite may occur though generally mild.
Diarrhea as a less common gastrointestinal side effect.
Irritation and itching around the rectal area due to bowel habit changes.
Possible tongue irritation or oral discomfort related to substance contact.
Rare cases of fecal impaction if hydration is inadequate.
Black, tarry stools or blood in stool in cases of severe irritation or bleeding.
Easy bruising or unusual bleeding possibly related to vitamin K malabsorption.
Potential dental enamel erosion or tooth discoloration from prolonged exposure to suspension.
Hypovitaminosis (especially fat-soluble vitamins A, D, E, K) due to malabsorption.
Severe constipation or bowel obstruction in predisposed individuals.
Allergic reactions including urticaria, angioedema, and rarely anaphylaxis.
Worsening of gastrointestinal motility disorders or pre-existing constipation.
Potential malabsorption of co-administered oral medications leading to reduced efficacy.

Precautions

Use cautiously in patients with pre-existing constipation or gastrointestinal motility disorders.
Monitor for signs of vitamin A, D, E, and K deficiency; consider supplementation.
Take other oral medications either one hour before or four to six hours after cholestyramine to avoid absorption interference.
Patients with phenylketonuria (PKU) should be aware that some formulations contain phenylalanine.
Ensure adequate hydration to prevent severe constipation or fecal impaction.
Careful dental hygiene is advised due to potential for enamel erosion and tooth discoloration.
Dose adjustments may be necessary in elderly patients who have increased constipation risk.
Use caution in patients with biliary obstruction or chronic liver diseases.
Monitor coagulation parameters in patients on warfarin as cholestyramine may affect vitamin K absorption.
Pregnant and breastfeeding women may require vitamin supplementation due to malabsorption.
Regular monitoring of lipid profile and liver function tests should be performed during therapy.
Consider potential interactions with fat-soluble vitamins and other fat-soluble drugs.
Patients should report any unusual bleeding or bruising promptly.
Avoid use in patients with mechanical intestinal or biliary tract obstruction.
Inform healthcare providers about cholestyramine use prior to any surgery or invasive procedures.

Warnings

Contraindicated in patients with complete biliary obstruction or gastrointestinal obstruction.
Risk of serious constipation or bowel obstruction if not accompanied by adequate fluid intake.
May cause interference with absorption of other medications, leading to reduced effectiveness.
Use with caution in hepatic impairment or severe liver disease.
Potential vitamin deficiency due to impaired fat-soluble vitamin absorption; monitor periodically.
May exacerbate pre-existing gastrointestinal symptoms such as bloating and abdominal pain.
Not recommended for primary use in patients with hypertriglyceridemia as it may increase triglyceride levels.
Potential for dental damage if powder suspension is held in the mouth too long or consumed improperly.
Use with caution in patients with clotting disorders due to vitamin K malabsorption.
When switching from other bile acid sequestrants, ensure proper washout to avoid compounded effects.
Pregnant women should only use if clearly needed and under supervision due to unknown fetal risks.
Excessive dosing can result in severe constipation or intestinal obstruction requiring medical attention.
Discontinue use and seek immediate medical attention if signs of serious allergic reactions occur.
Careful assessment and monitoring are advised in polypharmacy patients due to interaction potential.
Cholestyramine may interfere with diagnostic stool tests; inform healthcare providers accordingly.

Contraindication

Known hypersensitivity or allergy to cholestyramine or any component of the formulation.
Complete biliary obstruction or bile duct blockage.
Mechanical intestinal obstruction or significant constipation where bowel movement is impaired.
Phenylketonuria patients should avoid formulations containing phenylalanine.
History of severe fecal impaction or bowel obstruction with bile acid sequestrants.
Patients with hypersensitivity to other bile acid sequestrants.
Severe hypertriglyceridemia or hyperlipoproteinemia type III due to possible triglyceride increase.
Use is contraindicated if there is a history of hypersensitivity to the powder or excipients.
Not indicated in patients with impaired swallowing or inability to mix suspension adequately.
Avoid in patients with conditions where increased biliary excretion or bile acid binding is harmful.
Contraindicated in those who cannot maintain adequate hydration during therapy.
Not recommended in neonates or infants due to safety concerns and lack of data.
Patients with severe malabsorption syndromes should not use cholestyramine.
Patients with narrow-angle glaucoma or urinary retention should avoid therapy due to resin effects.
Concurrent use with other cationic exchange resins may be contraindicated due to additive effects.

Drug Interactions

May reduce absorption and effectiveness of oral medications such as digoxin and digitalis glycosides.
Interferes with absorption of warfarin and other vitamin K antagonists, affecting anticoagulation.
Reduces efficacy of thyroid medications like levothyroxine if not dosed apart properly.
Decreases bioavailability of phenobarbital, potentially requiring dose adjustment.
Interacts with certain antibiotics like tetracycline, reducing antibiotic absorption.
May reduce the effectiveness of birth control pills and hormone replacement therapy.
Concomitant use with diuretics such as spironolactone and thiazides requires monitoring of electrolytes.
Phenylbutazone absorption may be decreased when given with cholestyramine.
May reduce plasma concentrations of propranolol and other beta-blockers.
Vitamin supplements containing fat-soluble vitamins may show reduced absorption.
Simultaneous administration with penicillin G may require dose spacing to maintain efficacy.
Potential interference with absorption of fat-soluble drugs and vitamins necessitates staggered dosing schedules.
Co-administration with statins generally safe but efficacy to be monitored closely.
May impair the absorption of oral hypoglycemics requiring dosage monitoring.
Interactions with herbal supplements containing fat-soluble ingredients possible; monitor patient status.

Preparations Of The Drug

Cholestyramine powder packets: typically 4 grams of resin per packet for oral suspension.
Bulk powder formulations for compounding or bulk dispensing with specific dosing measurements.
Combination powders containing cholestyramine resin with flavoring agents for palatability.
Suspension prepared by mixing powder with water, broth, applesauce, or crushed pineapple for administration.
Some formulations contain small amounts of sugars and artificial sweeteners to enhance taste.
Questran Light: a lower-fat formulation variant with modified resin composition.
Generic cholestyramine powders available equivalent in potency and formulation to Questran.
Packets and bulk containers designed for convenient administration in outpatient and inpatient settings.
Manufactured resin formulated as a strongly basic anion exchange resin in the chloride form.
Resin composed of cross-linked polystyrene divinylbenzene copolymers modified with quaternary ammonium groups.
Available as off-white to yellowish powder with characteristic odor, insoluble in water but forming suspensions.
Standard packaging includes multiple packets per box, facilitating dose titration and compliance.
Mixing instructions emphasize use of non-carbonated liquids or appropriate foods to ensure palatability.
Storage conditions: room temperature, away from moisture and heat to maintain potency and ease of use.
In some countries, preparations may contain additional flavorings or excipients specific to manufacturer.