Drug & supplement interaction

Lacticaseibacillus Paracasei + Metronidazole

Metronidazole brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, and others.

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

Lacticaseibacillus Paracasei has a moderate interaction with Metronidazole. Theoretically, taking Lacticaseibacillus paracasei with antibiotic drugs might decrease the effectiveness of L.

Read the full interaction report
SeverityModerate
LikelihoodProbable
EvidenceD
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Lacticaseibacillus Paracasei and Metronidazole

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Metronidazole

Metronidazole falls under ANTIBIOTIC DRUGS — the group Lacticaseibacillus Paracasei interacts with.

Theoretically, taking Lacticaseibacillus paracasei with antibiotic drugs might decrease the effectiveness of L. paracasei.
L. paracasei preparations usually contain live and active organisms. Therefore, simultaneously taking antibiotics might kill a significant number of the organisms. Tell patients to separate administration of antibiotics and L. paracasei preparations by at least two hours.
Severity Moderate Likelihood Probable Evidence D

Interaction 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..

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

Here's the key thing to know: this interaction runs in one direction, and it's the probiotic that loses out, not your antibiotic. Metronidazole (Flagyl) will still work just fine to clear your infection. But since L. paracasei is made of live bacteria, an antibiotic that kills bacteria can wipe out a good chunk of those probiotic organisms if you swallow them at the same time.

The practical fix is simple: space them out by at least two hours. Many people actually take a probiotic while on antibiotics to help with the loose stools or stomach upset that drugs like metronidazole can cause, and that's reasonable. This concern is based on pharmacology reasoning rather than hard studies, so don't stress over it. If you want a plan that fits your situation, your pharmacist can help you time them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.

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

Lacticaseibacillus Paracasei Also Interacts With Other Medications

Lacticaseibacillus Paracasei has 181 moderate known drug interactions in our database — the Metronidazole one above is one of them. If you take anything else, check it against the full list below.

Moderate 181 No known interaction 2,649 (incl. Metronidazole)
Taking anything else?

Check Another of Your Medications Against Lacticaseibacillus Paracasei

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

From our Q&A

Questions About Lacticaseibacillus Paracasei or Metronidazole

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Lacticaseibacillus Paracasei or Metronidazole, 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 Metronidazole

This page covers Lacticaseibacillus Paracasei only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metronidazole page lists 83 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 7 major · 63 moderate · 13 minor.

From our pharmacist’s overview on the Metronidazole page

“Metronidazole (Flagyl) can stretch the heart's QT interval on its own, and most of the seven major-rated interactions among its 83 flagged supplement ingredients do the same thing, so I read this list with more wariness than most antibiotics earn. Grapefruit and ephedra stand out for adding to that heart-rhythm risk, while activated ch…”

Reviewed by 2 · Jul 18, 2026

Open the Metronidazole interaction page

How much people look this up

Where Lacticaseibacillus Paracasei and Metronidazole 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 Lacticaseibacillus Paracasei
Steady interest

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

29 days ago today
Medication Metronidazole
Top half

#972 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 Lacticaseibacillus Paracasei

What is Lacticaseibacillus Paracasei?

  • Digestive health and regularity
  • Immune support
  • Diarrhea (including antibiotic-associated)
  • Allergy and eczema symptoms
  • Gut microbiome balance

Lacticaseibacillus paracasei (formerly Lactobacillus paracasei) is a probiotic bacterium found in fermented foods and supplements that is widely used to support gut and immune health. Some strains have promising research for digestion, diarrhea, and allergies, but results vary by strain and many uses are not firmly proven. It is generally well tolerated in healthy people, but those who are seriously ill or immune-compromised should check with a doctor first.

Read the full Lacticaseibacillus Paracasei monograph & all interactions
Medication

About Metronidazole

What Is Metronidazole Used For?

Brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, MetroGel, Flagyl IV, Metronidazole Redi-Infusion, Flagyl IV RTU, Metro IV, Anabact, Metrosa, Metrotop, Noritate, Rozex Cream, Rozex Gel, Zyomet, Likmez

Metronidazole treats infections caused by certain parasites and by bacteria that grow without oxygen (anaerobic bacteria). Which use applies depends on the product.

Oral products (tablets, capsules and Likmez suspension) are used for trichomoniasis, a sexually transmitted infection. Likmez is also used for amebiasis and for anaerobic bacterial infections in adults. Metronidazole injection treats serious anaerobic infections. Vaginal gels treat bacterial vaginosis. Topical cream and lotion treat rosacea.

See full Metronidazole drug information
Keep checking

Other Drugs & Lacticaseibacillus Paracasei

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

0Major
181Moderate
0Minor
2,648No known interaction
181 Moderate 2,648 No interaction
Moderate

181 interactions

Showing 60 of 181 moderate interactions — see all 181 on the Lacticaseibacillus Paracasei page.

No interaction 2,648 drugs checked — show the list

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

Showing the 60 most looked-up of 2,648 medications checked with no known interaction — see the full Lacticaseibacillus Paracasei list.

See the full Lacticaseibacillus Paracasei interactions page
See every supplement checked against Metronidazole, 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
Lacticaseibacillus Paracasei monograph › Uses, safety, and every drug interaction in one place Metronidazole supplement interactions › Every supplement checked against Metronidazole, ranked by severity Metronidazole 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 Lacticaseibacillus Paracasei and Metronidazole Together: Common Questions

Can you take Lacticaseibacillus Paracasei with Metronidazole?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Lacticaseibacillus Paracasei and Metronidazole interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Metronidazole and Lacticaseibacillus Paracasei?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.