Drug & supplement interaction

Lacticaseibacillus Casei + Methenamine Mandelate, Potassium Acid Phosphate

Methenamine Mandelate, Potassium Acid Phosphate brand name: Thiacide.

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

Lacticaseibacillus Casei has a moderate interaction with Methenamine Mandelate, Potassium Acid Phosphate. Theoretically, taking Lacticaseibacillus casei 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

Lacticaseibacillus Casei and Methenamine Mandelate, Potassium Acid Phosphate

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

Moderate

ANTIBIOTIC DRUGS

Why this applies to Methenamine Mandelate, Potassium Acid Phosphate

Methenamine Mandelate, Potassium Acid Phosphate falls under ANTIBIOTIC DRUGS — the group Lacticaseibacillus Casei interacts with.

Theoretically, taking Lacticaseibacillus casei with antibiotic drugs might decrease the effectiveness of L. casei.
L. casei 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. casei 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: this interaction works against your probiotic, not your medicine. Methenamine mandelate is an antibacterial used to keep urine clear of infection (it forms formaldehyde in acidic urine to kill germs), and the potassium acid phosphate keeps your urine acidic so it works. Because Lacticaseibacillus casei is a live, friendly bacterium, anything with antibacterial action could kill off some of those organisms and make the probiotic less effective.

The good news is this is theoretical, based on how these products behave rather than strong studies. Your urinary medicine should keep working normally. To give the probiotic its best shot, a common tip is to space them out by about two hours. Check with your pharmacist if you want to be sure about 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

Lacticaseibacillus Casei Also Interacts With Other Medications

Lacticaseibacillus Casei has 181 moderate known drug interactions in our database — the Methenamine Mandelate, Potassium Acid Phosphate 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, Potassium Acid Phosphate)
Taking anything else?

Check Another of Your Medications Against Lacticaseibacillus Casei

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

Everything else you take

See Every Supplement That Interacts With Methenamine Mandelate, Potassium Acid Phosphate

This page covers Lacticaseibacillus Casei only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methenamine Mandelate, Potassium Acid Phosphate 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 Mandelate, Potassium Acid Phosphate page

“Activated charcoal is the single entry here I would flag first for anyone on Thiacide (methenamine mandelate with potassium acid phosphate), a urinary antiseptic taken to keep bladder infections from returning, and this list as a whole calls for real vigilance. Charcoal binds medicines in the gut and can sharply cut how much of the dru…”

Reviewed by 2 · Jul 18, 2026

Open the Methenamine Mandelate, Potassium Acid Phosphate interaction page

How much people look this up

Where Lacticaseibacillus Casei and Methenamine Mandelate, Potassium Acid Phosphate 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 Casei
Steady interest

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

29 days ago today
Medication Methenamine Mandelate, Potassium Acid Phosphate
Top 10%

#146 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 Casei

What is Lacticaseibacillus Casei?

  • Digestive health
  • Diarrhea (including antibiotic-related)
  • Immune support
  • Constipation
  • Gut microbiome balance

Lacticaseibacillus casei (formerly Lactobacillus casei) is a 'friendly' probiotic bacterium found in fermented foods and many supplements. It is most studied for digestive issues like diarrhea, where some evidence is encouraging, but results vary by strain and condition. It is generally well tolerated in healthy people, but those with weakened immune systems should check with a doctor first.

Read the full Lacticaseibacillus Casei monograph & all interactions
Keep checking

Other Drugs & Lacticaseibacillus Casei

Browse every other medication we’ve checked against Lacticaseibacillus Casei — 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 Casei page.

No interaction 2,648 drugs checked — show the list

We also checked Lacticaseibacillus Casei 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 Casei list.

See the full Lacticaseibacillus Casei interactions page
See every supplement checked against Methenamine Mandelate, Potassium Acid Phosphate, 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 Casei monograph › Uses, safety, and every drug interaction in one place Methenamine Mandelate, Potassium Acid Phosphate supplement interactions › Every supplement checked against Methenamine Mandelate, Potassium Acid Phosphate, ranked by severity 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 Casei and Methenamine Mandelate, Potassium Acid Phosphate Together: Common Questions

Can you take Lacticaseibacillus Casei with Methenamine Mandelate, Potassium Acid Phosphate?
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 Casei and Methenamine Mandelate, Potassium Acid Phosphate 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, Potassium Acid Phosphate and Lacticaseibacillus Casei?

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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.