Drug & supplement interaction

Genistein Combined Polysaccharide + Mefenamic Acid

Mefenamic Acid brand name: Ponstel.

Minor Interaction
Medically reviewed by · Updated June 2023
The bottom line Minor

Genistein Combined Polysaccharide has a minor interaction with Mefenamic Acid. Some evidence suggests that genistein can alter the pharmacokinetics of CYP2C9 substrates and should be used cautiously with them.

Read the full interaction report
SeverityMinor
LikelihoodPossible
EvidenceC
What do Severity, Likelihood & Evidence mean?
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Interaction report

Genistein Combined Polysaccharide and Mefenamic Acid

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

Minor

Cytochrome P450 2C9 (Cyp2C9) Substrates

Why this applies to Mefenamic Acid

Mefenamic Acid falls under Cytochrome P450 2C9 (Cyp2C9) Substrates — the group Genistein Combined Polysaccharide interacts with.

Some evidence suggests that genistein can alter the pharmacokinetics of CYP2C9 substrates and should be used cautiously with them. This has only been seen in animal studies however. (PUBMED https://pubmed.ncbi.nlm.nih.gov/29387488/)
Severity Minor Likelihood Possible Evidence C

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 short version: your body relies on a liver enzyme called CYP2C9 to clear mefenamic acid (Ponstel). The genistein in GCP may slow that enzyme down a bit, at least in the lab. If that happened in people, mefenamic acid could hang around longer and you might notice more of its usual NSAID side effects, like stomach upset, heartburn, nausea, or in some cases stomach irritation or bleeding.

That said, I don't want you to worry too much. This effect has only shown up in animal studies, the rating on file is minor, and the evidence is weak. Mefenamic acid is also usually taken short-term for pain or cramps. Still, since you're considering GCP for a hormone-related reason, please run both past your oncologist or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction

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

Genistein Combined Polysaccharide Also Interacts With Other Medications

Genistein Combined Polysaccharide has 29 moderate, 110 minor known drug interactions in our database — the Mefenamic Acid one above is one of them. If you take anything else, check it against the full list below.

Moderate 29 Minor 110 No known interaction 2,691 (incl. Mefenamic Acid)
Taking anything else?

Check Another of Your Medications Against Genistein Combined Polysaccharide

Covers the 2,830 medications we’ve checked against Genistein Combined Polysaccharide. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Mefenamic Acid

This page covers Genistein Combined Polysaccharide only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Mefenamic Acid page lists 118 supplements it has a documented interaction with, worst first, each one explained.

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

By severity: 5 major · 86 moderate · 27 minor.

From our pharmacist’s overview on the Mefenamic Acid page

“Mefenamic acid (Ponstel), an NSAID mostly used for menstrual cramps and short-term pain, has a supplement list that earns genuine caution, and the five major-rated entries are where to start. Beer and wine are two of them, because alcohol plus any NSAID raises the risk of stomach and intestinal bleeding.”

Reviewed by 2 · Jul 18, 2026

Open the Mefenamic Acid interaction page

How much people look this up

Where Genistein Combined Polysaccharide and Mefenamic Acid 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 Genistein Combined Polysaccharide
Top half

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

29 days ago today
Medication Mefenamic Acid
Top 25%

#680 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 Genistein Combined Polysaccharide

What is Genistein Combined Polysaccharide?

  • Prostate cancer support
  • Bladder cancer support
  • Breast cancer support
  • Hormone-related cancers
  • Immune support

Genistein Combined Polysaccharide (GCP) is a soy-and-mushroom supplement studied mostly for hormone-related cancers like prostate cancer, but solid human evidence is still limited. It should never replace standard cancer treatment, and you should talk with your oncologist and pharmacist before using it, especially if you have a hormone-sensitive condition.

Read the full Genistein Combined Polysaccharide monograph & all interactions
Medication

About Mefenamic Acid

What Is Mefenamic Acid Used For?

Brand name: Ponstel

Mefenamic acid capsules are approved to manage mild to moderate pain in adults and adolescents 14 years of age and older, but only for short-term use — no longer than 7 days.

They are also approved to treat primary dysmenorrhea (painful menstrual periods), started at the onset of bleeding and associated symptoms.

See full Mefenamic Acid drug information
Keep checking

Other Drugs & Genistein Combined Polysaccharide

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

0Major
29Moderate
110Minor
2,690No known interaction
29 Moderate 110 Minor 2,690 No interaction
Moderate

29 interactions

Minor

110 interactions

Showing 60 of 110 minor interactions — see all 110 on the Genistein Combined Polysaccharide page.

No interaction 2,690 drugs checked — show the list

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

Showing the 60 most looked-up of 2,690 medications checked with no known interaction — see the full Genistein Combined Polysaccharide list.

See the full Genistein Combined Polysaccharide interactions page
See every supplement checked against Mefenamic Acid, 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
Genistein Combined Polysaccharide monograph › Uses, safety, and every drug interaction in one place Mefenamic Acid supplement interactions › Every supplement checked against Mefenamic Acid, ranked by severity Mefenamic Acid 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 Genistein Combined Polysaccharide and Mefenamic Acid Together: Common Questions

Can you take Genistein Combined Polysaccharide with Mefenamic Acid?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Genistein Combined Polysaccharide and Mefenamic Acid interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Mefenamic Acid and Genistein Combined Polysaccharide?

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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.