Drug & supplement interaction

Galacto-oligosaccharides (gos) + Mercaptopurine

Mercaptopurine brand name: Purixan.

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

Galacto-oligosaccharides (gos) has a moderate interaction with Mercaptopurine. Theoretically, GOS might reduce the effects of immunosuppressants.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Galacto-oligosaccharides (gos) and Mercaptopurine

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

Moderate

IMMUNOSUPPRESSANTS

Why this applies to Mercaptopurine

Mercaptopurine falls under IMMUNOSUPPRESSANTS — the group Galacto-oligosaccharides (gos) interacts with.

Theoretically, GOS might reduce the effects of immunosuppressants.
Human and animal studies suggest that GOS may stimulate the immune system. This could theoretically alter the effects of immunosuppressant medications.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thinking behind this one. Mercaptopurine works partly by calming down or suppressing certain immune cells, which is why it's used in leukemia. GOS, the prebiotic fiber, may gently nudge your immune system the other way by feeding helpful gut bacteria. So on paper, GOS could work against what mercaptopurine is trying to do, possibly making it a little less effective.

I want to be honest with you though: this is theoretical only, based on how things work in the lab, not from real cases of people on mercaptopurine. Since this is a serious cancer medicine where steady, reliable effects really matter, please don't add a GOS supplement without first checking with your oncologist or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Bakker-Zierikzee AM, Tol EA, Kroes H, et al. Faecal sIgA secretion in infants fed on pre- or probiotic infant formula. Pediatr Allergy Immunol 2006;17(2):134-140. PubMed
  2. Vos AP, Haarman M, Buco A, et al. A specific prebiotic oligosaccharide mixture stimulates delayed-type hypersensitivity in a murine influenza vaccination model. Int Immunopharmacol 2006;6(8):1277-1286. PubMed

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

Galacto-oligosaccharides (gos) Also Interacts With Other Medications

Galacto-oligosaccharides (gos) has 120 moderate known drug interactions in our database — the Mercaptopurine one above is one of them. If you take anything else, check it against the full list below.

Moderate 120 No known interaction 2,710 (incl. Mercaptopurine)
Taking anything else?

Check Another of Your Medications Against Galacto-oligosaccharides (gos)

Covers the 2,830 medications we’ve checked against Galacto-oligosaccharides (gos). Pick one to open its full report.

From our Q&A

Questions About Galacto-oligosaccharides (gos) or Mercaptopurine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Galacto-oligosaccharides (gos) or Mercaptopurine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Mercaptopurine

This page covers Galacto-oligosaccharides (gos) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Mercaptopurine page lists 106 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 Active Hexose Correlated Compound (ahcc) (moderate).

By severity: 4 major · 92 moderate · 10 minor.

From our pharmacist’s overview on the Mercaptopurine page

“Mercaptopurine (Purixan) works by deliberately suppressing the immune system, whether for leukemia or inflammatory bowel disease, and the supplement interactions on this page deserve genuine care rather than a quick skim. Two problems dominate.”

Reviewed by 2 · Jul 18, 2026

Open the Mercaptopurine interaction page

How much people look this up

Where Galacto-oligosaccharides (gos) and Mercaptopurine 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 Galacto-oligosaccharides (gos)
Steady interest

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

29 days ago today
Medication Mercaptopurine
Steady interest

#1,865 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 Galacto-oligosaccharides (gos)

What is Galacto-oligosaccharides (gos)?

  • Prebiotic to support gut bacteria
  • Constipation
  • Digestive health
  • Immune support
  • Infant gut health

Galacto-oligosaccharides (GOS) are a type of prebiotic fiber that feed the helpful bacteria in your gut. They are generally well tolerated and may help with digestive regularity and gut balance, though they can cause gas and bloating, especially at higher doses. Evidence is promising but still limited for many uses, so talk with your pharmacist or doctor before starting.

Read the full Galacto-oligosaccharides (gos) monograph & all interactions
Medication

About Mercaptopurine

What Is Mercaptopurine Used For?

Brand name: Purixan

Mercaptopurine — available as a tablet and as an oral suspension — is used to treat acute lymphoblastic leukemia (ALL), a type of blood cancer. It is given as part of a combination chemotherapy maintenance regimen, meaning it works alongside other cancer medicines to keep leukemia in remission.

Both the tablet form and the oral suspension form carry this indication for adult and pediatric patients. The oral suspension is particularly useful for patients who cannot swallow tablets.

See full Mercaptopurine drug information
Keep checking

Other Drugs & Galacto-oligosaccharides (gos)

Browse every other medication we’ve checked against Galacto-oligosaccharides (gos) — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
120Moderate
0Minor
2,709No known interaction
120 Moderate 2,709 No interaction
Moderate

120 interactions

Showing 60 of 120 moderate interactions — see all 120 on the Galacto-oligosaccharides (gos) page.

No interaction 2,709 drugs checked — show the list

We also checked Galacto-oligosaccharides (gos) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,709 medications checked with no known interaction — see the full Galacto-oligosaccharides (gos) list.

See the full Galacto-oligosaccharides (gos) interactions page
See every supplement checked against Mercaptopurine, 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
Galacto-oligosaccharides (gos) monograph › Uses, safety, and every drug interaction in one place Mercaptopurine supplement interactions › Every supplement checked against Mercaptopurine, ranked by severity Mercaptopurine 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 Galacto-oligosaccharides (gos) and Mercaptopurine Together: Common Questions

Can you take Galacto-oligosaccharides (gos) with Mercaptopurine?
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 Galacto-oligosaccharides (gos) and Mercaptopurine 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 Mercaptopurine and Galacto-oligosaccharides (gos)?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.