Drug & supplement interaction

Lactobacillus Johnsonii + Methenamine Hippurate

Methenamine Hippurate brand names: Urex, Hiprex.

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

Lactobacillus Johnsonii has a moderate interaction with Methenamine Hippurate. 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 Methenamine Hippurate

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Methenamine Hippurate

Methenamine Hippurate 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 thing to keep in mind: this interaction works against your probiotic, not your medication. Methenamine hippurate (Hiprex, Urex) works by turning into formaldehyde in acidic urine to keep urinary tract infections in check. Lactobacillus johnsonii is made up of live bacteria, and since methenamine acts as a mild antibacterial agent, taking them at the same time could kill off some of those helpful probiotic organisms before they get a chance to settle in your gut.

This is a theoretical concern based on how the two work, not something proven in studies, so don't be alarmed. Your UTI protection from Hiprex stays intact. To give the probiotic a fair shot, a simple fix is to space them apart by at least two hours. As always, your pharmacist can help you set up the best timing.

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 Methenamine Hippurate 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. Methenamine Hippurate)
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 Methenamine Hippurate

This page covers Lactobacillus Johnsonii only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methenamine Hippurate page lists 44 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Bacillus Coagulans (moderate), Bacillus Subtilis (moderate), Bifidobacterium Animalis Subsp. Lactis (moderate) and Bifidobacterium Bifidum (moderate).

By severity: 1 major · 33 moderate · 10 minor.

From our pharmacist’s overview on the Methenamine Hippurate page

“Most people taking methenamine hippurate (Hiprex, Urex) use it daily to prevent repeat urinary tract infections, and many also take probiotics, which is where the bulk of this 44-ingredient list sits. Even so, the page deserves real vigilance, because one entry is rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Methenamine Hippurate 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 Methenamine Hippurate 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 Methenamine Hippurate 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

#1,365 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Methenamine Hippurate
Steady interest

#1,764 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 Methenamine

What Is Methenamine Used For?

Brand names: Urex, Hiprex

Methenamine is used to suppress or prevent frequently recurring urinary tract infections (UTIs), including pyelonephritis (kidney infection) and cystitis (bladder infection). It is intended for long-term or ongoing use after another antibiotic has already cleared the active infection — not as a first treatment for a new, acute infection.

Methenamine Mandelate (available as an oral solution and tablet) is also indicated for infected residual urine that can occur with certain neurologic diseases. It is not appropriate as the sole treatment when an infection is causing systemic symptoms like chills and fever.

See full Methenamine 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 Methenamine Hippurate, 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 Methenamine Hippurate supplement interactions › Every supplement checked against Methenamine Hippurate, ranked by severity Methenamine 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 Methenamine Hippurate Together: Common Questions

Can you take Lactobacillus Johnsonii with Methenamine Hippurate?
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 Methenamine Hippurate 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 Methenamine Hippurate 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.