Drug & supplement interaction

Lactobacillus Jensenii + Methenamine Mandelate

Methenamine Mandelate brand names: Mandelamine, Methimazole.

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

Lactobacillus Jensenii has a moderate interaction with Methenamine Mandelate. Theoretically, taking Lactobacillus jensenii 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 Jensenii and Methenamine Mandelate

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Methenamine Mandelate

Methenamine Mandelate falls under ANTIBIOTIC DRUGS — the group Lactobacillus Jensenii interacts with.

Theoretically, taking Lactobacillus jensenii with antibiotic drugs might decrease the effectiveness of L. jensenii.
Lactobacillus jensenii 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. jensenii 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: methenamine mandelate works as a urinary antiseptic. Once it reaches acidic urine, it releases formaldehyde, which kills bacteria in the urinary tract. That same germ-fighting action is the catch when it comes to a probiotic like Lactobacillus jensenii. Because the probiotic is made of live, active bacteria, an antibacterial agent can knock out a chunk of those organisms before they ever do their job.

This concern is theoretical, based on how the two work rather than on strong human studies, so don't be alarmed. The medicine still treats your infection normally. To give the probiotic a fair shot, a common suggestion is to space them out by at least two hours. Check with your pharmacist or doctor to confirm the best timing for you.

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 Jensenii Also Interacts With Other Medications

Lactobacillus Jensenii has 181 moderate known drug interactions in our database — the Methenamine Mandelate 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 Mandelate)
Taking anything else?

Check Another of Your Medications Against Lactobacillus Jensenii

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

Everything else you take

See Every Supplement That Interacts With Methenamine Mandelate

This page covers Lactobacillus Jensenii only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methenamine Mandelate page lists 91 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Siberian Cocklebur (major), Wine (major) and Ascophyllum Nodosum (moderate).

By severity: 4 major · 77 moderate · 10 minor.

From our pharmacist’s overview on the Methenamine Mandelate page

“People take methenamine mandelate (Mandelamine) day after day to keep urinary tract infections at bay, and that long habit is exactly why the 91 supplements on this page deserve genuine vigilance. Four carry a major rating, and most of those point at the liver: Siberian cocklebur has been linked to outright liver failure, and heavy bee…”

Reviewed by 2 · Jul 18, 2026

Open the Methenamine Mandelate interaction page

How much people look this up

Where Lactobacillus Jensenii and Methenamine Mandelate 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 Jensenii
Top half

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

29 days ago today
Medication Methenamine Mandelate
Top half

#996 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 Jensenii

What is Lactobacillus Jensenii?

  • Vaginal health
  • Maintaining healthy vaginal flora
  • Bacterial vaginosis support
  • Yeast infection support
  • General probiotic use

Lactobacillus jensenii is one of the natural 'good' bacteria found in a healthy vagina, and it is sometimes added to probiotic products marketed for vaginal health. While its role in the body is well recognized, there is only limited human research on taking it as a supplement, so the benefits are not proven. Talk with your pharmacist or doctor before using it, especially if you have a weakened immune system.

Read the full Lactobacillus Jensenii monograph & all interactions
Medication

About Methimazole

What Is Methimazole Used For?

Brand names: Mandelamine, Methimazole

Methimazole tablets are used in adults and children with hyperthyroidism (an overactive thyroid) due to Graves' disease or toxic multinodular goiter when surgery or radioactive iodine is not the right option. They work to lower thyroid hormone levels and ease symptoms.

Methimazole tablets are also used to bring thyroid hormone levels down before a patient undergoes thyroidectomy (thyroid surgery) or radioactive iodine treatment, making those procedures safer.

See full Methimazole drug information
Keep checking

Other Drugs & Lactobacillus Jensenii

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

No interaction 2,648 drugs checked — show the list

We also checked Lactobacillus Jensenii 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 Jensenii list.

See the full Lactobacillus Jensenii interactions page
See every supplement checked against Methenamine Mandelate, 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 Jensenii monograph › Uses, safety, and every drug interaction in one place Methenamine Mandelate supplement interactions › Every supplement checked against Methenamine Mandelate, ranked by severity Methimazole 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 Jensenii and Methenamine Mandelate Together: Common Questions

Can you take Lactobacillus Jensenii with Methenamine Mandelate?
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 Jensenii and Methenamine Mandelate 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 Mandelate and Lactobacillus Jensenii?

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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.