Drug & supplement interaction

Lactobacillus Johnsonii + Gentamicin (IV)

Gentamicin (IV) brand name: Garamycin.

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

Lactobacillus Johnsonii has a moderate interaction with Gentamicin (IV). Theoretically, taking Lactobacillus johnsonii with antibiotic drugs might decrease the effectiveness of L.

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

Lactobacillus Johnsonii and Gentamicin (IV)

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Gentamicin (IV)

Gentamicin (IV) falls under ANTIBIOTIC DRUGS — the group Lactobacillus Johnsonii interacts with.

Theoretically, taking Lactobacillus johnsonii with antibiotic drugs might decrease the effectiveness of L. johnsonii.
Lactobacillus johnsonii 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. johnsonii 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 simple version: gentamicin is a powerful antibiotic, and it doesn't know the difference between bad bacteria and the friendly probiotic bacteria in a Lactobacillus johnsonii supplement. So if you take them around the same time, the gentamicin can wipe out a good chunk of those live probiotic organisms before they ever get a chance to do their job. This works one direction only: it's your probiotic that loses its punch, not your gentamicin.

The good news is your antibiotic still works just fine, so your infection treatment isn't at risk. This concern is theoretical, based on how these two interact in principle. If you want the probiotic to count, talk with your pharmacist about spacing the doses, often at least two hours apart.

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

Lactobacillus Johnsonii Also Interacts With Other Medications

Lactobacillus Johnsonii has 181 moderate known drug interactions in our database — the Gentamicin (IV) 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. Gentamicin (IV))
Taking anything else?

Check Another of Your Medications Against Lactobacillus Johnsonii

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

Everything else you take

See Every Supplement That Interacts With Gentamicin (IV)

This page covers Lactobacillus Johnsonii only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Gentamicin (IV) page lists 35 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Asarabacca (major), Siberian Cocklebur (major), Aristolochia (moderate), Bacillus Coagulans (moderate) and Bacillus Subtilis (moderate).

By severity: 2 major · 31 moderate · 2 minor.

From our pharmacist’s overview on the Gentamicin (IV) page

“Kidney protection is the reason this list deserves real attention. Gentamicin (Garamycin) is an IV antibiotic that can stress the kidneys on its own, and both of the major-rated entries among the 35 supplements on file share that same weakness.”

Reviewed by 2 · Jul 18, 2026

Open the Gentamicin (IV) interaction page

One more smart check

Taking Lactobacillus Johnsonii as Part of a Dietary Supplement Product? Check It for Interactions

We hold 17 real supplement products containing Lactobacillus Johnsonii, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lactobacillus Johnsonii. Your product may carry other ingredients that interact with Gentamicin (IV) too, on top of Lactobacillus Johnsonii — 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 Lactobacillus Johnsonii and Gentamicin (IV) 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 Lactobacillus Johnsonii
Steady interest

#1,345 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Gentamicin (IV)
Steady interest

#2,446 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 Lactobacillus Johnsonii

What is Lactobacillus Johnsonii?

  • Digestive and gut health
  • Supporting healthy gut bacteria
  • Diarrhea prevention or relief
  • Immune support
  • Helping with stomach (H. pylori) discomfort

Lactobacillus johnsonii is a probiotic bacterium found naturally in the human gut and in some fermented foods, and it is used mainly for digestive and immune support. Human evidence for most specific health claims is still limited, so its benefits are uncertain. It is generally well tolerated in healthy people, but anyone with a weakened immune system, serious illness, or who is pregnant should talk to a pharmacist or doctor first.

Read the full Lactobacillus Johnsonii monograph & all interactions
Medication

About Gentamicin Topical

What Is Gentamicin Topical Used For?

Brand name: Garamycin

Gentamicin sulfate topical is used to treat primary skin infections — infections that start directly in the skin — such as impetigo contagiosa, superficial folliculitis (infected hair follicles), furunculosis (boils), ecthyma, sycosis barbae, and pyoderma gangrenosum.

It also treats secondary skin infections, where bacteria have moved into already-irritated or damaged skin. This includes infected eczema, infected contact dermatitis (like poison ivy that gets infected), pustular acne, pustular psoriasis, infected seborrheic dermatitis, and bacterial infections on top of fungal or viral skin conditions. It has also been used successfully for infected stasis ulcers, infected superficial burns, infected insect bites and stings, infected lacerations and abrasions, paronychia (infected nail folds), and wounds from minor surgery.

See full Gentamicin Topical drug information
Keep checking

Other Drugs & Lactobacillus Johnsonii

Browse every other medication we’ve checked against Lactobacillus Johnsonii — 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 Lactobacillus Johnsonii page.

No interaction 2,648 drugs checked — show the list

We also checked Lactobacillus Johnsonii 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 Lactobacillus Johnsonii list.

See the full Lactobacillus Johnsonii interactions page
See every supplement checked against Gentamicin (IV), 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
Lactobacillus Johnsonii monograph › Uses, safety, and every drug interaction in one place Gentamicin (IV) supplement interactions › Every supplement checked against Gentamicin (IV), ranked by severity Gentamicin Topical 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 Lactobacillus Johnsonii and Gentamicin (IV) Together: Common Questions

Can you take Lactobacillus Johnsonii with Gentamicin (IV)?
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 Lactobacillus Johnsonii and Gentamicin (IV) 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 Gentamicin (IV) and Lactobacillus Johnsonii?

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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.