Saccharomyces boulardii Recommended Dose
For prevention of antibiotic-associated diarrhea and Clostridioides difficile infection in adults, administer Saccharomyces boulardii 1 gram daily (approximately 3 × 10¹⁰ CFU/day), started at the initiation of antibiotic therapy and continued throughout the entire antibiotic course. 1
Adult Dosing by Indication
Antibiotic-Associated Diarrhea Prevention
- Standard dose: 1 gram daily (3 × 10¹⁰ CFU/day) 2, 1
- Timing: Begin at antibiotic initiation and continue for the entire antibiotic duration 1
- Rationale: S. boulardii is a yeast and therefore not killed by antibiotics, ensuring continuous probiotic exposure throughout treatment 1
- Efficacy: Reduces antibiotic-associated diarrhea risk from 18.7% to 8.5% (RR: 0.47; 95% CI: 0.38-0.57, NNT: 10) 3
Recurrent Clostridioides difficile Infection
- Dose: 1 gram daily (3 × 10¹⁰ CFU/day) 2
- Administration: Given as adjunct to standard antibiotic therapy (vancomycin or metronidazole) 2
- Evidence: May increase cessation of diarrhea (RR: 1.33; 95% CI: 1.02-1.74) and decrease recurrence (RR: 0.59; 95% CI: 0.35-0.98), though evidence quality is low 2
- Important caveat: The IDSA/SHEA guidelines note that S. boulardii has shown promise but has not demonstrated significant and reproducible efficacy in controlled trials for CDI recurrence prevention 2
Traveler's Diarrhea Prevention
Pediatric Dosing (≥6 months)
Children and Adolescents
- Standard dose: 250 mg twice daily (500 mg total daily) 5
- Timing: Throughout antibiotic course 5
- Efficacy: Reduces antibiotic-associated diarrhea from 20.9% to 8.8% (RR: 0.43; 95% CI: 0.3-0.6) 3
- CDI prevention: Reduces C. difficile-associated diarrhea in children (RR: 0.25; 95% CI: 0.08-0.73) 3
Critical Safety Considerations
Absolute Contraindications
Do not use S. boulardii in the following populations due to risk of fungemia: 1
- Immunocompromised patients
- Critically ill patients
- Patients with central venous catheters
- Cardiac valvular disease
- Premature neonates
Evidence Quality and Guideline Positions
The American Gastroenterological Association (AGA) provides a conditional recommendation for S. boulardii based on low-quality evidence, but notes substantial clinical benefit in appropriate populations. 1
- AGA position: Conditional recommendation for S. boulardii specifically, as it was the only single-strain probiotic showing significant reduction in C. difficile-associated diarrhea across multiple trials 1
- IDSA/SHEA position: States insufficient data to recommend probiotics for primary CDI prevention outside clinical trials, though acknowledges some promise 2
- Evidence heterogeneity: Studies vary in recruitment criteria (initial vs. recurrent CDI), antibiotic regimens, and outcome measures, limiting pooled analysis 2
Common Pitfalls to Avoid
- Strain specificity matters: Not all probiotics are interchangeable; efficacy is highly strain-specific 1
- Do not use as monotherapy: S. boulardii should not replace standard antibiotic therapy for established CDI 1
- Elderly patients: One negative trial in elderly hospitalized patients showed no benefit, highlighting that efficacy may vary by population 6
- Timing is critical: Must be started at antibiotic initiation, not after diarrhea develops 1
Clinical Decision Algorithm
High-risk patients who benefit most from prophylaxis: 1
- Baseline CDI risk >15%
- Elderly patients
- Prolonged hospitalization
- Severe underlying illness
- Previous CDI infection
For these high-risk immunocompetent adults receiving antibiotics, prescribe S. boulardii 1 gram daily starting with the first antibiotic dose and continuing throughout the entire antibiotic course. 1