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Saccharomyces boulardii

Probiotic yeast with Cochrane support for preventing antibiotic-associated diarrhoea and reducing C. difficile recurrence.

Why

Saccharomyces boulardii is a non-pathogenic probiotic yeast, pharmacologically distinct from bacterial probiotics. The Cochrane review of probiotics for prevention of antibiotic-associated diarrhoea found S. boulardii reduced AAD risk in adults and children. Separate evidence supports its use in reducing recurrence of Clostridioides difficile infection (alongside antibiotics) and in shortening acute infectious diarrhoea.

How it works

Resists antibiotic killing (a yeast, most antibiotics target bacteria), binds and neutralises C. difficile toxins A and B via a 54-kDa protease, restores brush-border enzyme activity, and modulates intestinal IgA. Cleared from the gut within 3–5 days of stopping intake, does not colonise.

Expected onset · Effect on AAD prevention requires concurrent dosing with antibiotics; acute diarrhoea symptom reduction within 2–4 days

How to take

Dosage

Adult: 250–500 mg twice daily during antibiotic course and 1–2 weeks after. Acute diarrhoea: 250 mg twice daily. Paediatric: per product label, weight-banded.

Timing

Separated from antifungals by at least 2 hours; otherwise with or without food

On the label

Specifically 'Saccharomyces boulardii' (often CNCM I-745 strain). Stable at room temperature unlike many bacterial probiotics.

Ideal for

Adults and children starting antibiotic courses; people with a history of recurrent C. difficile (alongside antibiotic therapy under supervision); travellers' diarrhoea prevention.

Safety

Avoid in critically ill, immunocompromised, central-line-bearing, or severely ill patients, rare fungaemia reports in this group. Not with antifungal medication (fluconazole, etc.). Pregnancy data limited; generally considered safe but coordinate with the prescribing clinician.

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Evidence

At a glance

Cochrane 2017 SR (33 RCTs, n=6,352 paediatric): S. boulardii reduced antibiotic-associated diarrhoea (NNT~10). Szajewska 2015 Aliment Pharmacol Ther meta-analysis (21 RCTs): pooled relative risk 0.47 vs control for AAD in adults and children. McFarland 2010 confirmed reduced C. difficile recurrence as adjunct to antibiotics.

Where to get it

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