Drug & supplement interaction

Bifidobacterium Breve + Methylnaltrexone

Methylnaltrexone brand name: Relistor.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Bifidobacterium Breve and Methylnaltrexone in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Methylnaltrexone states a food rule worth keeping to, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Bifidobacterium Breve and Methylnaltrexone

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Methylnaltrexone and Bifidobacterium Breve in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Bifidobacterium Breve safety at a glance

Bifidobacterium Br... overall Use caution Generally well tolerated in healthy people, but caution is needed for those who are very ill or immunocompromised.
Pregnancy Use caution Probiotics are often considered low-risk, but evidence is limited, so use only with your doctor's guidance.
Breastfeeding Use caution Limited safety data exist, so check with your healthcare provider before use.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Methylnaltrexone and Bifidobacterium Breve? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Methylnaltrexone

Interactions in our licensed database are recorded against drug classes, not just single drug names. Methylnaltrexone is filed under a single classification — cytochrome p450 2d6 (cyp2d6) inhibitors. Bifidobacterium Breve has documented interactions with 1 drug class — the most serious being antibiotic drugs (moderate) — and none of Methylnaltrexone’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Bifidobacterium Breve Does Interact With Other Medications

Bifidobacterium Breve has 182 moderate known drug interactions in our database — Methylnaltrexone isn’t one of them. If you take anything else, check it against the full list below.

Moderate 182 No known interaction 2,648 (incl. Methylnaltrexone)
Taking anything else?

Check Another of Your Medications Against Bifidobacterium Breve

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

What to actually watch for

No Interaction Found — But Data Suggests Bifidobacterium Breve and Methylnaltrexone May Share a Side Effect

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas Additional detail

    Bifidobacterium Breve

    “Bloating and flatulence have been reported with probiotic use; however, these adverse effects have not been reported from ingestion of Bifidobacterium breve in particular.”

    Bifidobacterium Breve · Natural Medicines adverse-effect record, reported in flatulence.

    Methylnaltrexone

    Listed in the ADVERSE REACTIONS section of the FDA label for Methylnaltrexone. Read the label on DailyMed ›

Reported for Bifidobacterium Breve but not commonly for Methylnaltrexone: a higher chance of infection and a bowel blockage.

Effects for Methylnaltrexone come from the ADVERSE REACTIONS section of its FDA label; effects for Bifidobacterium Breve come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

How to take them

Some Methylnaltrexone Products Have a Food Rule — Bifidobacterium Breve Should Not Break It

At least one FDA label for a product containing Methylnaltrexone says to take it on an empty stomach. Most supplements — Bifidobacterium Breve included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Methylnaltrexone on its own and move Bifidobacterium Breve to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Methylnaltrexone products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

o In patients with chronic non-cancer pain and OIC, take RELISTOR tablets with water on an empty stomach at least 30 minutes before the first meal of the day.

From the Dosage and Administration section of the FDA label we read for Methylnaltrexone — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

Overlapping uses

What Methylnaltrexone Is Prescribed For, and What Bifidobacterium Breve Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Methylnaltrexone is a prescription medicine with approved uses on its FDA label. Bifidobacterium Breve is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Methylnaltrexone is prescribed for: Methylnaltrexone, sold as Relistor, treats opioid-induced constipation (OIC) — constipation caused by opioid pain medications. Both Relistor tablets and Relistor injection are approved for adults with chronic non-cancer pain, including those with pain related to a prior cancer or its treatment who do not need frequent opioid dose increases. Relistor injection is also approved for adults with advanced illness or active cancer pain who require increasing opioid doses as part of palliative care.

Bifidobacterium Breve has been studied for:

  • Constipation studied, not established Bifidobacterium Breve has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Bifidobacterium Breve for constipation

    Most early research shows that oral Bifidobacterium breve seems to be beneficial for constipation.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Methylnaltrexone on your own; if you are taking Bifidobacterium Breve for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

Everything else you take

See Every Supplement That Interacts With Methylnaltrexone

This page covers Bifidobacterium Breve only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Methylnaltrexone page lists 3 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Fever Bark (moderate), Iboga (moderate) and Yohimbe (moderate).

By severity: 3 moderate.

From our pharmacist’s overview on the Methylnaltrexone page

“If you take methylnaltrexone (Relistor) for opioid-induced constipation, the supplement list to know is short: three ingredients, all rated moderate, none major. Yohimbe, fever bark, and iboga are all cleared by the same liver enzyme, CYP2D6, and methylnaltrexone can slow that enzyme, letting their active compounds build up in your blood.”

Reviewed by 2 · Jul 18, 2026

Open the Methylnaltrexone interaction page

One more smart check

Taking Bifidobacterium Breve as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,771 real supplement products containing Bifidobacterium Breve, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Bifidobacterium Breve. Even though Bifidobacterium Breve itself has no known interaction with Methylnaltrexone, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Bifidobacterium Breve and Methylnaltrexone 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 Bifidobacterium Breve
Top 25%

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

29 days ago today
Medication Methylnaltrexone
Steady interest

#2,186 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Bifidobacterium Breve reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Bifidobacterium Breve and Methylnaltrexone records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Bifidobacterium Breve

What is Bifidobacterium Breve?

  • Digestive health and regularity
  • Infant colic and gut support
  • Diarrhea (including antibiotic-related)
  • Constipation
  • General immune and gut microbiome support

Bifidobacterium breve is a 'friendly' gut bacterium taken as a probiotic, most often to support digestion and balance the gut microbiome. Some studies suggest possible benefits for certain digestive and infant conditions, but evidence is still limited and varies by strain. It is generally well tolerated in healthy people, but anyone with a weak immune system or serious illness should check with a doctor or pharmacist first.

Bifidobacterium breve · Bifidobacteriaceae · Live bacterial cells (probiotic strain) · Capsules, powders, sachets, chewables, drops, and fortified foods or drinks

An interaction check asks whether these two react with each other — it does not ask whether Bifidobacterium Breve is a good idea for someone in your situation. Here is what our Bifidobacterium Breve record says about it on its own.

Bifidobacterium Breve: dosing

There is no single standard dose of Bifidobacterium breve. Probiotic amounts are usually measured in colony-forming units (CFU), and products vary widely in their strain and strength.The best approach is to follow the directions on the product label, since dosing was often based on the specific strain studied.

From our Bifidobacterium Breve monograph — the full record covers uses, side effects and every documented interaction.

Read the full Bifidobacterium Breve monograph & all interactions
Medication

About Methylnaltrexone

What Is Methylnaltrexone Used For?

Brand name: Relistor

Methylnaltrexone, sold as Relistor, treats opioid-induced constipation (OIC) — constipation caused by opioid pain medications. Both Relistor tablets and Relistor injection are approved for adults with chronic non-cancer pain, including those with pain related to a prior cancer or its treatment who do not need frequent opioid dose increases.

Relistor injection is also approved for adults with advanced illness or active cancer pain who require increasing opioid doses as part of palliative care.

See full Methylnaltrexone drug information
Keep checking

Other Drugs & Bifidobacterium Breve

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

0Major
182Moderate
0Minor
2,647No known interaction
182 Moderate 2,647 No interaction
Moderate

182 interactions

Showing 60 of 182 moderate interactions — see all 182 on the Bifidobacterium Breve page.

No interaction 2,647 drugs checked — show the list

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

Showing the 60 most looked-up of 2,647 medications checked with no known interaction — see the full Bifidobacterium Breve list.

See the full Bifidobacterium Breve interactions page
See every supplement checked against Methylnaltrexone, ranked by severity
Evidence & sources

Bifidobacterium Breve References

The 9 references that drive our Bifidobacterium Breve monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.
  2. Xiao JZ, Takahashi S, Odamaki T, et al. Antibiotic susceptibility of bifidobacterial strains distributed in the Japanese market. Biosci Biotechnol Biochem. 2010;74(2):336-42. PubMed
  3. Pruccoli G, Silvestro E, Pace Napoleone C, Aidala E, Garazzino S, Scolfaro C. Are probiotics safe? Bifidobacterium bacteremia in a child with severe heart failure. Infez Med. 2019;27(2):175-178.
  4. Ohishi A, Takahashi S, Ito Y, et al. Bifidobacterium septicemia associated with postoperative probiotic therapy in a neonate with omphalocele. J Pediatr. 2010;156(4):679-81. PubMed
  5. Sakurai Y, Watanabe T, Miura Y, et al. Clinical and bacteriologic characteristics of six cases of Bifidobacterium breve bacteremia due to probiotic administration in the neonatal intensive care unit. Pediatr Infect Dis J 2022;41(1):62-65. PubMed
  6. Esaiassen E, Hjerde E, Cavanagh JP, Simonsen GS, Klingenberg C; Norwegian Study Group on Invasive Bifidobacterial Infections. Bifidobacterium bacteremia: Clinical characteristics and a genomic approach to assess pathogenicity. J Clin Microbiol. 2017;55(7) PubMed
  7. Wakabayashi Y, Nakayama S, Yamamoto A, et al. First case of necrotizing fasciitis and bacteremia caused by Bifidobacteriumbreve. Anaerobe 2022;76:102613.
  8. Takeda Y, Ota K, Kondo A, et al. A case of necrotizing fasciitis caused by Bifidobacterium breve. IDCases 2022;31:e01667. PubMed
  9. Suwantarat N, Romagnoli M, Wakefield T, Carroll KC. Ventriculoperitoneal shunt infection caused by Bifidobacterium breve. Anaerobe 2014;28:1-3. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Bifidobacterium Breve and Methylnaltrexone Together: Common Questions

Is it safe to take Bifidobacterium Breve with Methylnaltrexone?
We do not list a known interaction between Bifidobacterium Breve and Methylnaltrexone. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Bifidobacterium Breve and Methylnaltrexone have any of the same side effects?
Yes — our sources link each of them separately to one of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Should I take Bifidobacterium Breve and Methylnaltrexone at the same time of day?
At least one FDA label for a product containing Methylnaltrexone says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Methylnaltrexone on its own and move Bifidobacterium Breve to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.
Are Bifidobacterium Breve and Methylnaltrexone used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Bifidobacterium Breve in each. That is a conversation for your prescriber, especially if Methylnaltrexone is being adjusted to a target.
How was the Bifidobacterium Breve and Methylnaltrexone combination checked?
Interactions in our licensed database are recorded against drug classes. Methylnaltrexone is filed under 1 classification, and Bifidobacterium Breve has documented interactions with 1 drug class — none of Methylnaltrexone's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Bifidobacterium Breve interact with any other medications?
Yes. Bifidobacterium Breve has 182 documented drug interactions in our database — Methylnaltrexone is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Methylnaltrexone interact with any supplements?
Yes. Methylnaltrexone has documented interactions with 3 supplements in our database — Bifidobacterium Breve is not one of them. The Methylnaltrexone interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Bifidobacterium Breve monograph Uses, safety profile, and every drug interaction in one place Methylnaltrexone drug information The full plain-English guide to this medication Methylnaltrexone supplement interactions Every supplement checked against Methylnaltrexone, 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 References The 9 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Methylnaltrexone and Bifidobacterium Breve?

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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.