Bile acid sequestrant (lipid-lowering)
Cholestyramine is a medicine used to lower cholesterol, indicated when diet alone is not enough. It acts in the gut: it binds bile acids and prevents their reabsorption, which leads the liver to use more cholesterol to make new bile acids, lowering blood cholesterol. It is not absorbed by the body.
Also known as: Colestiramina, Questran
Digoxin + cholestyramine: the resin binds digoxin in the gut and reduces its absorption (QUADRO 2: digitalis glycosides — possibly digoxin).
Cholestyramine (anion-exchange resin) binds digoxin in the intestinal lumen, reducing its absorption and potentially lowering plasma concentrations. QUADRO 2 of Annex 7 records this interaction in the bile-acid resin section. The effect is attenuated if doses are separated: give digoxin at least 4 hours before or after cholestyramine. In practice, the interaction is most relevant when cholestyramine is started or stopped in stabilised patients — stopping may increase digoxin absorption and precipitate toxicity. Monitor digoxin levels and clinical effect in the weeks after resin therapy changes.
Cholestyramine + digoxin: adsorption of digoxin in the intestinal lumen — reduced absorption and effect; separate dosing by 4 hours and monitor.
Bile acid sequestrant resins bind, in the digestive tract, to orally administered drugs, including digitalis glycosides — reduced digoxin absorption (QUADRO 2, Bile acids — resins: "Digitalis glycosides: possibly digoxin").
Monitor digoxin levels when starting/stopping cholestyramine.
Subtherapeutic digoxin levels and worsening HF with cholestyramine.
Separate dosing (digoxin 2 h before or 4-6 h after cholestyramine) and monitor digoxin levels.
Prontuário Terapêutico do INFARMED (11th ed., 2012) — Annex 7, QUADRO 2 (Bile acids — resins)
Mycophenolate + cholestyramine: cholestyramine binds mycophenolate in the gut and reduces its absorption, potentially decreasing drug exposure — separate doses.
DailyMed (CellCept) documents interaction studies with cholestyramine, and QUADRO 2 of the Prontuário (Bile acids — sequestering resins) lists mycophenolate among drugs whose absorption can be reduced by the resins. Cholestyramine binds mycophenolate in the gut lumen and interferes with the enterohepatic recirculation of mycophenolic acid, reducing systemic exposure.
Watch immunosuppressive efficacy (MPA levels when available; signs of rejection) during the combination.
Signs of graft rejection or MPA levels below target with simultaneous intake.
Give mycophenolate at least 1-2 hours before or 4 hours after cholestyramine; ideally space the two doses as far apart as possible.
DailyMed/FDA (NIH/NLM) — approved CellCept label (Genentech), section 7.1: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=37241e87-4af4-4dc3-a1aa-ea6f20d8dc40 ; Prontuário Terapêutico do INFARMED (11th ed., 2012) — Annex 7, Table 2 (Bile acids — sequestering resins)
Ursodeoxycholic acid + cholestyramine: cholestyramine reduces ursodiol absorption — separate doses by 4-6 hours.
The FDA ursodiol label documents in the interactions section that bile acid sequestering agents may interfere with the action of ursodiol by reducing its absorption ("Bile Acid Sequestering Agents: May interfere with the action of ursodiol tablets by reducing its absorption", 7.1). Cholestyramine binds bile acids and other molecules in the gut lumen, reducing the oral bioavailability of ursodeoxycholic acid given simultaneously. The clinical consequence is loss of efficacy in gallstone disease and primary biliary cholangitis — the patient may not respond to the usual dose. The practical guidance is to separate the doses: give ursodiol at least 1 hour before or 4-6 hours after cholestyramine, and assess clinical response. The same precaution applies to other sequestrants (colestipol, colesevelam).
Ursodeoxycholic acid + cholestyramine: cholestyramine reduces ursodiol absorption — separate doses by 4-6 hours.
The FDA ursodiol label documents: "Bile Acid Sequestering Agents: May interfere with the action of ursodiol tablets by reducing its absorption" (7.1). Cholestyramine binds bile acids in the gut lumen and reduces the absorption of orally administered ursodiol, compromising its effect in gallstone disease.
Assess clinical response (biliary symptoms, ultrasound follow-up when applicable) during the combination.
Lack of response in gallstone treatment with simultaneous intake.
Give ursodeoxycholic acid at least 1 hour before or 4-6 hours after cholestyramine; ideally space by 4-6 hours.
DailyMed/FDA (NIH/NLM) — approved Ursodiol label (BLUEPOINT LABORATORIES), section 7.1: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3c98080-0a4d-4a93-8dcb-02ab8533050b ; approved Cholestyramine label (ASCEND LABORATORIES): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=430ac07e-8524-4dec-a599-b7ebc56d9563
FDA label (PRECAUTIONS, Drug Interactions): because cholestyramine binds bile acids, it may interfere with normal fat digestion and absorption and prevent absorption of fat-soluble vitamins (A, D, E, K) — in long-term use, consider supplementation with water-miscible (or parenteral) forms.
In long-term use, consider supplementation of fat-soluble vitamins (A, D, E, K); separate vitamin supplements from cholestyramine dosing.
DailyMed/FDA (NIH/NLM) — approved Cholestyramine label, PRECAUTIONS/Drug Interactions section: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=430ac07e-8524-4dec-a599-b7ebc56d9563
FDA label (CONTRAINDICATIONS): cholestyramine is contraindicated in patients with complete biliary obstruction where bile is not secreted into the intestine — without bile acids in the lumen, the drug mechanism of action does not apply.
Contraindicated in complete biliary obstruction; the pruritus indication is limited to partial biliary obstruction.
DailyMed/FDA (NIH/NLM) — approved Cholestyramine label, CONTRAINDICATIONS section: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=430ac07e-8524-4dec-a599-b7ebc56d9563
FDA label (Pregnancy Category C): no adequate and well-controlled studies in pregnant women. Not systemically absorbed, but interferes with absorption of fat-soluble vitamins — regular prenatal supplementation may not be adequate during use.
Category C: use only if benefit justifies risk; ensure fat-soluble vitamin supplementation.
Caution in breastfeeding: the possible poor vitamin absorption (Pregnancy section) may affect nursing infants.
Not applicable (no specific contraception documented).
DailyMed/FDA (NIH/NLM) — approved Cholestyramine label, Pregnancy/Nursing Mothers section: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=430ac07e-8524-4dec-a599-b7ebc56d9563
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Lipid-lowering by bile acid sequestration: the faecal loss of bile acids leads to increased oxidation of cholesterol to bile acids, with reduction of beta-lipoprotein/LDL and serum cholesterol (FDA label CLINICAL PHARMACOLOGY). In partial biliary obstruction, it reduces serum bile acid levels and pruritus.
The resin adsorbs and combines with bile acids in the intestine, forming an insoluble complex excreted in the faeces — partially interrupting the enterohepatic circulation of bile acids. It is not absorbed from the digestive tract.
Absorption: none — "Cholestyramine resin is not absorbed from the digestive tract" (DESCRIPTION). The profile is therefore exclusively local/intestinal.
Not metabolised — acts in the gut lumen with no systemic absorption.
Half-life not applicable (non-absorbed drug; no systemic exposure).
