How should I prescribe cholestyramine (Questran) for an adult patient with chronic or intermittent diarrhea suspected to be due to bile‑acid malabsorption?

How to Prescribe Cholestyramine (Questran) for Diarrhea

Start cholestyramine at 4 grams once daily (one packet or scoop), taken with meals, and gradually titrate upward every 1-4 weeks based on response, up to a maximum of 24 grams daily divided into 2-4 doses. 1, 2

Initial Prescription Details

Starting Dose

• Begin with 4 grams (one packet/scoop) once daily 2
• For patients with pre-existing constipation: start with 4 grams once daily for 5-7 days before increasing 2
• Mix each dose in 2-6 ounces of water or non-carbonated beverage; never take dry 2

Titration Strategy

Increase gradually to minimize side effects (bloating, constipation, nausea) which occur in up to 45% of patients 1:

• Increase by one dose daily at monthly intervals 2
• Typical maintenance: 8-16 grams daily (2-4 packets) divided into 2 doses 2
• Maximum: 24 grams daily (6 packets) 2
• Assess response at 4-week intervals minimum 2

Timing and Administration

• Take at mealtime to maximize bile acid binding 2
• Other medications must be taken 1 hour before OR 4-6 hours after cholestyramine to avoid binding interactions 2
• This is critical for warfarin, thyroid medications, digitalis, thiazides, and fat-soluble vitamins 2

Expected Response

Approximately 70% of patients with bile acid diarrhea respond to cholestyramine 1, with most seeing improvement within days to weeks 3, 4. Response rates are similar across different severities of bile acid malabsorption 1.

Long-Term Management

Maintenance Strategy

Once symptoms are controlled:

• Try intermittent, on-demand dosing rather than continuous daily use 1
• Use the lowest effective dose to minimize side effects 1
• About 60% of responders can transition to as-needed dosing 1, 4
• However, 94% may experience recurrence if stopped completely 1

Duration of Treatment

This is typically a chronic condition requiring long-term therapy 3:

• Median treatment duration in studies: 6-15 years 3
• Only 15% achieve spontaneous remission 4

Important Caveats and Contraindications

Do NOT Use Cholestyramine If:

• Extensive ileal resection (>100 cm) - may worsen steatorrhea and cause significant caloric loss 1
• Extensive ileal Crohn's disease with active inflammation 1

Monitor and Supplement:

• Fat-soluble vitamins (A, D, E, K) - cholestyramine impairs absorption with chronic use 2
• Consider water-miscible or parenteral vitamin supplementation for long-term therapy 2
• Folic acid supplementation may be needed 2
• Encourage increased fluid and fiber intake to prevent constipation 2

Drug Interactions:

Review all concurrent medications - cholestyramine binds many drugs including warfarin, thyroid hormones, digitalis, thiazides, and oral contraceptives 2. Strict separation of dosing times is mandatory.

If Cholestyramine Fails or Is Not Tolerated

Switch to colesevelam (625 mg tablets, 3 tablets twice daily) as second-line bile acid sequestrant 1:

• Better tolerability profile (tablet vs powder) 1
• Similar efficacy (73% response rate) 1
• More expensive, so reserved for second-line 1

If all bile acid sequestrants fail, use alternative antidiarrheal agents (loperamide, diphenoxylate) for symptomatic control 1.

Sample Prescription

Cholestyramine 4 grams powder
Sig: Mix one packet in 2-6 oz water or juice once daily with breakfast
Disp: 30 packets
Refills: 2
Instructions: Take all other medications 1 hour before or 4-6 hours after this medication. May increase to twice daily after one week if diarrhea persists.

1, 2