What is the correct dose of ursodeoxycholic acid (Ursofalk) using 250‑mg tablets for a 45‑kg woman with a 1.2‑cm asymptomatic gallstone?

Ursodeoxycholic Acid Dosing for Gallstone Dissolution in a 45 kg Woman

For a 45 kg woman with a 1.2 cm gallstone, the recommended dose is 360–450 mg daily (approximately 250 mg twice daily using available 250 mg tablets), given in 2–3 divided doses for 6–24 months, though laparoscopic cholecystectomy remains the definitive treatment and should be strongly considered first. 1

Critical Patient Selection Criteria

Before prescribing ursodeoxycholic acid, verify this patient meets ALL of the following criteria, as treatment will fail otherwise:

• Stone size ≤15 mm (1.5 cm): This patient's 1.2 cm stone meets the size requirement 2, 3
• Radiolucent (cholesterol) stones: Must be confirmed on imaging—calcified or pigment stones will not dissolve 2, 1
• Floating stones on oral cholecystography: This indicates cholesterol-rich composition and predicts 83.3% efficacy 3
• Functioning gallbladder with patent cystic duct: Must visualize on oral cholecystogram 2
• Patient refuses or cannot undergo surgery: Ursodiol should only be used when surgery is declined or contraindicated 2

Exact Dosing Calculation

Weight-Based Dosing

• FDA-approved dose: 8–10 mg/kg/day for gallstone dissolution 1
• For 45 kg patient: 360–450 mg/day total dose
• Practical regimen with 250 mg tablets: 250 mg twice daily (500 mg/day) 1, 4

Dosing Schedule

• Divide into 2–3 doses daily to maintain steady bile acid levels 1
• Practical option: 250 mg in morning + 250 mg at bedtime
• Alternative: 250 mg three times daily if better tolerated (750 mg/day remains within safe range) 4

Treatment Duration and Monitoring

Expected Timeline

• Minimum treatment: 6 months before assessing response 1
• Typical duration: 6–24 months for complete dissolution 2, 5
• First ultrasound: At 6 months to assess partial dissolution 1

Critical Decision Point at 12 Months

• If no partial dissolution by 12 months: Discontinue ursodiol—likelihood of success is greatly reduced 1
• If partial dissolution seen: Continue therapy and confirm complete dissolution with repeat ultrasound 1–3 months after apparent dissolution 1

Why Surgery Should Be Discussed First

Laparoscopic cholecystectomy provides superior outcomes and should be the primary recommendation:

• Immediate, permanent stone removal with mortality rate of 0.054% in low-risk women under 49 years 2
• No recurrence risk: Ursodiol has 50% stone recurrence rate within 84 months after successful dissolution 5
• Prevents future complications: Eliminates risk of acute cholecystitis, cholangitis, or pancreatitis 2
• Shorter time to resolution: Surgery provides immediate relief versus 6–24 months of daily medication 2, 1

Common Pitfalls to Avoid

Do NOT Use Ursodiol If:

• Stone >15 mm: Dissolution is ineffective and delays definitive treatment 2
• Patient is pregnant: Ursodiol is contraindicated during pregnancy 2
• Acute cholecystitis present: Requires urgent cholecystectomy within 7–10 days, not medical management 2
• Calcified stones on imaging: These will not dissolve regardless of dose 1, 5

Monitoring Requirements

• Ultrasound at 6-month intervals for first year 1
• Liver function tests: Should remain normal throughout treatment 5
• Side effects: <1% experience transient diarrhea that does not require discontinuation 5

Expected Outcomes

Success Rates

• Overall dissolution: 30–80% depending on stone characteristics 5
• Optimal candidates (small, floating, radiolucent stones): 83.3% efficacy 3
• This patient's 1.2 cm stone: Falls within favorable size range for dissolution 3

Biochemical Changes During Treatment

• Biliary cholesterol saturation decreases significantly 5, 6
• Lithogenic index becomes unsaturated in successful cases 3
• No hepatotoxicity: Liver function tests remain normal 5, 3

Practical Summary for This Patient

Start with 250 mg twice daily (morning and bedtime), obtain ultrasound at 6 months, and discontinue if no response by 12 months. However, strongly counsel this patient that laparoscopic cholecystectomy offers immediate, permanent resolution with excellent safety profile, whereas medical therapy requires 6–24 months of daily medication with 50% recurrence risk even after successful dissolution. 2, 1, 5