When should I start taking it?

On the first day of the antibiotic. Starting after diarrhoea has begun misses most of the benefit, which is preventive.

Do I need to space it from my antibiotic?

No. S. boulardii is a yeast and antibacterial antibiotics do not affect it, unlike bacterial probiotics.

How much does it reduce my risk?

In the pooled trials the risk fell from about 19 percent to 8.5 percent, roughly one avoided episode for every thirteen people treated.

How long should I continue?

Through the antibiotic course and for about a week afterwards, while the bacterial community re-establishes.

Who should not take it?

Anyone significantly immunocompromised, critically ill, with a central venous catheter or with a yeast allergy. Fungaemia has been reported in these groups.

Is it the same as a normal probiotic?

No. Most probiotics are bacteria and are killed by antibiotics. S. boulardii is a yeast, which is why it works during a course.

Outcome

Strong Evidence

Effectiveness 4/5

Saccharomyces Boulardii for Diarrhea Prevention

S. boulardii roughly halves the risk of antibiotic-associated diarrhoea and is the best-studied single organism for this purpose.

Overview

Verdict

Strong yes

Two meta-analyses covering thousands of participants show S. boulardii roughly halves the risk of antibiotic-associated diarrhoea in children and adults, with a number needed to treat of about 13.

How It Works

Downstream effects

Yeast, so unaffected by antibacterial antibiotics

Secretes protease that degrades C. difficile toxins A and B

Inactivates gram-negative endotoxin

Stimulates secretory IgA and preserves tight junctions

Raises brush border disaccharidase activity

Transient: clears within days of stopping

Dosing & Protocol

Doses used in human trials

Population	Dose	Schedule	Notes
Adults, antibiotic-associated diarrhoea	250-500 mg (5-10 billion CFU)	Twice daily	Start with the antibiotic, continue for a week afterwards
Children	250 mg (5 billion CFU)	Once or twice daily	Widely used in the paediatric trial arms
Travellers diarrhoea prevention	250-500 mg	Daily, starting five days before travel	Lower and less consistent evidence than the antibiotic indication
Acute infectious diarrhoea	250-500 mg	Twice daily until symptoms resolve	Shortens duration by roughly one day in paediatric data

Doses are commonly expressed as milligrams of lyophilised yeast; 250 mg corresponds to about 5 billion CFU.

Simple protocol

1
Start on day one of the antibiotic
Starting late narrows the protective window; the benefit is prevention, not rescue.
2
Take 250-500 mg twice daily
No need to separate from the antibiotic, since the yeast is not affected by it.
3
Do not mix into hot drinks
Heat kills the yeast. Use cool or lukewarm liquid or take the capsule whole.
4
Continue for 7 days after finishing· Antibiotic course plus 1 week
Risk of diarrhoea persists after the course ends while bacteria recolonise.
5
Escalate if things worsen
Severe, bloody or persistent diarrhoea, or fever, needs medical assessment and C. difficile testing.

Evidence

Studies linked to this pairing.

Probiotics for the Prevention of Antibiotic-Associated Diarrhea in Outpatients: A Systematic Review and Meta-Analysis

Score: 7/10

2017

meta_analysis

Blaabjerg S, Artzi DM, Aabenhus R

Probiotics including S. boulardii reduced antibiotic-associated diarrhoea in outpatients, with a number needed to treat around 13.

View source

Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea

Score: 8/10

2015

meta_analysis

n=4780

Szajewska H, Kolodziej M

Saccharomyces boulardii reduced the risk of antibiotic-associated diarrhoea from about 19 percent to 8.5 percent across 21 randomised trials in children and adults.

View source

Absolute risk change: About 19 percent down to 8.5 percent for antibiotic-associated diarrhoea
Number needed to treat: Roughly 13 in the outpatient meta-analysis
Trials pooled: 21 randomised trials, 4,780 participants in children and adults
Trial dose: 250-500 mg (5-10 billion CFU) twice daily
Timing: Started with the antibiotic and continued through the course
Main limitation: Trials vary in antibiotic type and diarrhoea definition; benefit is prevention, not treatment of established C. difficile infection

Safety

Not for immunocompromised or catheterised patients

Fungaemia has been reported in critically ill, immunocompromised and central-line patients. Avoid S. boulardii in these groups, and do not open capsules near an indwelling catheter.

Interactions & Conflicts

Interactions and cautions

Interacts with	Severity	Mechanism	Action
Antifungal drugs (fluconazole, nystatin)	moderate	They kill the yeast and abolish its effect	There is no point taking both; separate the courses
Immunosuppression, neutropenia, transplant	high	Risk of yeast entering the bloodstream	Avoid
Central venous catheter	high	Reported contamination route for fungaemia	Avoid; do not open capsules nearby
Critical illness or intensive care	high	Documented fungaemia cases in this setting	Avoid unless a specialist advises otherwise
Hot drinks and food	low	Heat inactivates the live yeast	Take with cool or lukewarm liquid

References

Frequently Asked Questions

Medical Disclaimer

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Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.