NutriStack
Metronidazole and Saccharomyces Boulardii, a synergy.
Saccharomyces boulardii is a yeast probiotic with strong evidence for preventing antibiotic-associated diarrhea, and it is unaffected by metronidazole because it is fungal rather than bacterial. It is particularly useful during anaerobic-targeted therapy.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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What the row says.
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At a glance
- Substances
- Metronidazole and Saccharomyces Boulardii
- Pair type
- Synergy
- Evidence (highest tier)
- Strong
- Source citations
- 2 sources
- Stack Score effect
- +2 to your Stack Score (per scored synergy row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Synergy · Strong evidence
Synergy
What is happening. Saccharomyces boulardii is a yeast probiotic with strong evidence for preventing antibiotic-associated diarrhea, and it is unaffected by metronidazole because it is fungal rather than bacterial. It is particularly useful during anaerobic-targeted therapy.
Mechanism. S. boulardii produces proteases that degrade C. difficile toxins, stimulates secretory IgA, and competes with pathogens for intestinal adhesion sites. Being a yeast, it is intrinsically resistant to antibacterial drugs including metronidazole.
Recommendation. Take Saccharomyces boulardii throughout your metronidazole course. Timing flexibility is greater than with bacterial probiotics. Continue for at least 1 week after the antibiotic ends.
Sources (2)
- McFarland LV. Probiotics for the Primary and Secondary Prevention of C. difficile Infections: A Meta-analysis and Systematic Review. Antibiotics (Basel). 2015;4(2):160-78. PMID 27025619
- Boddy AV, Elmer GW, McFarland LV, Levy RH. Influence of antibiotics on the recovery and kinetics of Saccharomyces boulardii in rats. Pharm Res. 1991;8(6):796-800. PMID 2062812
Stack Score
How this pair moves the number.
Effect on the composite score
If both Metronidazole and Saccharomyces Boulardii are in the same stack, this pair applies +2 to your Stack Score (per scored synergy row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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