Cholestyramine is a bile acid sequestrant that works by binding bile acids in the intestine, preventing their reabsorption. This forces the liver to convert more cholesterol into bile acids, thereby reducing circulating low-density lipoprotein (LDL) cholesterol. The process upregulates hepatic LDL receptors, enhancing clearance of LDL from the bloodstream. This mechanism is well-documented in the Lippincott Textbook of Pharmacology and Lange Basic & Clinical Pharmacology.

1. Hyperlipidemia: First-line therapy for primary hypercholesterolemia, particularly in patients intolerant to statins or as adjunctive therapy.
2. Pruritus: Relieves itching associated with partial biliary obstruction (e.g., primary biliary cholangitis).
3. Diarrhea: Manages bile acid malabsorption-induced diarrhea (e.g., post-ileal resection, Crohn’s disease).
4. Off-Label: Occasionally used to bind toxins in Clostridioides difficile infection (British National Formulary [BNF]).

• Adults:
  • Initial Dose: 4 g once or twice daily.
  • Maintenance Dose: Gradually increase to 12–24 g/day in 1–4 divided doses.
• Administration:
  • Mix powder with water, juice, or non-carbonated beverage.
  • Take other medications 1 hour before or 4–6 hours after cholestyramine to avoid reduced absorption (BNF).

• Common:
  • Gastrointestinal: Constipation, bloating, flatulence, nausea.
  • Nutritional: Deficiencies in fat-soluble vitamins (A, D, E, K) with long-term use.
• Serious:
  • Hypertriglyceridemia (may elevate triglycerides).
  • Rare cases of intestinal obstruction or hyperchloremic acidosis (Lange Basic & Clinical Pharmacology).

• Contraindications: Complete biliary obstruction, bowel obstruction.
• Caution:
  • Use in pregnancy requires monitoring for vitamin K deficiency (risk of neonatal bleeding).
  • Avoid in severe renal impairment due to chloride load.
• Monitoring:
  • Lipid profile (baseline and every 4–8 weeks).
  • Vitamin levels (A, D, E, K) with prolonged use (BNF).

Cholestyramine binds to multiple drugs, reducing their absorption. Key interactions include:

• Warfarin: Reduced anticoagulant effect (monitor INR closely).
• Levothyroxine, Digoxin, Diuretics: Space doses 1 hour before or 4–6 hours after cholestyramine.
• Statins, Beta-Blockers, Antibiotics (e.g., tetracyclines): Potential reduced efficacy (Lippincott Textbook of Pharmacology).

• Generic Name: Cholestyramine.
• Brand Names: Questran (UK/US), Prevalite (US), Locholest (EU).

Conclusion
Cholestyramine remains a cornerstone therapy for hyperlipidemia and bile acid-related conditions. Its unique mechanism and safety profile make it suitable for statin-intolerant patients, though gastrointestinal side effects and drug interactions require careful management. Clinicians should adhere to guidelines from the BNF, Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to optimize patient outcomes