Drug & supplement interaction

Saccharomyces Boulardii + Ketoconazole

Ketoconazole brand name: Nizoral.

Minor Interaction
Medically reviewed by · Updated September 2026
The bottom line Minor

Saccharomyces Boulardii has a minor interaction with Ketoconazole. Theoretically, taking antifungals with Saccharomyces boulardii might decrease the effectiveness of Saccharomyces boulardii.

Read the full interaction report
SeverityMinor
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Saccharomyces Boulardii and Ketoconazole

Here is the interaction we found between these two, with the evidence behind it.

Minor

ANTIFUNGALS

Why this applies to Ketoconazole

Ketoconazole falls under ANTIFUNGALS — the group Saccharomyces Boulardii interacts with.

Theoretically, taking antifungals with Saccharomyces boulardii might decrease the effectiveness of Saccharomyces boulardii.
S. boulardii is a live yeast. Therefore, simultaneously taking antifungals might kill a significant number of the organisms.
Severity Minor Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: this interaction runs the opposite way from what people usually worry about. Ketoconazole won't be affected by the probiotic at all. Instead, the concern is that ketoconazole, which is an antifungal, may kill off some of your Saccharomyces boulardii, since that probiotic is actually a live yeast. In other words, your antifungal could make the probiotic less effective at doing its job, like helping with diarrhea.

I want to be honest about how solid this is: it's a theoretical concern based on how these drugs work, not something proven in studies, and it's rated minor. If you really want both to work, spacing them apart during the day may help. Check with your pharmacist or doctor before starting the probiotic, especially since live yeast isn't right for everyone.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lewis SJ, Freedman AR. Review article: the use of biotherapeutic agents in the prevention and treatment of gastrointestinal disease. Aliment Pharmacol Ther 1998;12:807-22. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Saccharomyces Boulardii Also Interacts With Other Medications

Saccharomyces Boulardii has 39 minor known drug interactions in our database — the Ketoconazole one above is one of them. If you take anything else, check it against the full list below.

Minor 39 No known interaction 2,791 (incl. Ketoconazole)
Taking anything else?

Check Another of Your Medications Against Saccharomyces Boulardii

Covers the 2,830 medications we’ve checked against Saccharomyces Boulardii. Pick one to open its full report.

From our Q&A

Questions About Saccharomyces Boulardii or Ketoconazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Saccharomyces Boulardii or Ketoconazole, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Ketoconazole

This page covers Saccharomyces Boulardii only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Ketoconazole page lists 182 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 135 moderate · 41 minor.

From our pharmacist’s overview on the Ketoconazole page

“Ketoconazole (Nizoral) is already hard on the liver, so treat its 182 interacting supplements with genuine care, starting with the six rated major. Most of the list runs through CYP3A4, the liver enzyme ketoconazole strongly blocks, so it can raise levels of over a hundred herbal ingredients, while grapefruit pushes ketoconazole itself…”

Reviewed by 2 · Jul 18, 2026

Open the Ketoconazole interaction page

One more smart check

Taking Saccharomyces Boulardii as Part of a Dietary Supplement Product? Check It for Interactions

We hold 608 real supplement products containing Saccharomyces Boulardii, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Saccharomyces Boulardii. Your product may carry other ingredients that interact with Ketoconazole too, on top of Saccharomyces Boulardii — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Saccharomyces Boulardii and Ketoconazole Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Saccharomyces Boulardii
Top 25%

#253 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Ketoconazole
Steady interest

#2,009 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Saccharomyces Boulardii

What is Saccharomyces Boulardii?

Saccharomyces Boulardii
  • Acute diarrhea
  • Antibiotic-associated diarrhea
  • Traveler's diarrhea
  • Preventing C. difficile recurrence
  • General gut health

Saccharomyces boulardii is a beneficial yeast used as a probiotic, with the strongest evidence for preventing and treating certain types of diarrhea, including antibiotic-associated diarrhea. It is generally well tolerated in healthy people, but those who are seriously ill or have weakened immune systems should avoid it because of rare but serious bloodstream infections. Talk with your pharmacist or doctor before starting it.

Read the full Saccharomyces Boulardii monograph & all interactions
Medication

About Ketoconazole

What Is Ketoconazole Used For?

Brand name: Nizoral

Ketoconazole 2% shampoo and foam are used to treat tinea versicolor (also called pityriasis versicolor) — a fungal infection caused by Pityrosporum orbiculare (also known as Malassezia furfur), a yeast that naturally lives on the skin.

This infection creates light or dark patches, most often on the trunk, neck, arms, and upper thighs. Even after the fungus is cleared, those skin patches may take months to return to their normal color — that's normal, and depends on your skin type and sun exposure. Tinea versicolor can also come back, since the fungus lives on healthy skin even when there's no active infection.

See full Ketoconazole drug information
Keep checking

Other Drugs & Saccharomyces Boulardii

Browse every other medication we’ve checked against Saccharomyces Boulardii — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
0Moderate
39Minor
2,790No known interaction
39 Minor 2,790 No interaction
Minor

39 interactions

No interaction 2,790 drugs checked — show the list

We also checked Saccharomyces Boulardii against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,790 medications checked with no known interaction — see the full Saccharomyces Boulardii list.

See the full Saccharomyces Boulardii interactions page
See every supplement checked against Ketoconazole, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Saccharomyces Boulardii monograph › Uses, safety, and every drug interaction in one place Ketoconazole supplement interactions › Every supplement checked against Ketoconazole, ranked by severity Ketoconazole drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Saccharomyces Boulardii and Ketoconazole Together: Common Questions

Can you take Saccharomyces Boulardii with Ketoconazole?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Saccharomyces Boulardii and Ketoconazole interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Ketoconazole and Saccharomyces Boulardii?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.