Drug & supplement interaction

Grape + Thiotepa

Thiotepa brand names: Thioplex, Tepadina.

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

Grape has a moderate interaction with Thiotepa. It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.

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

Grape and Thiotepa

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Thiotepa

Thiotepa falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Grape interacts with.

It is unclear if grape seed extract inhibits or induces CYP3A4; research is conflicting.
In vitro evidence suggests that grape seed extract might inhibit CYP3A4 enzymes. However, evidence from animal research shows that grape seed extract may induce CYP3A4 in the liver. So far, these interactions have not been reported in humans.
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 wrinkle with thiotepa: it's actually a prodrug. Your liver uses an enzyme called CYP3A4 to convert it into TEPA, the form that does much of the cancer-fighting work. So anything that nudges this enzyme can shift the balance between the parent drug and its active form.

Now, grape seed extract is a real question mark here. Lab dish studies hint it might block CYP3A4, while animal studies suggest it might speed it up. The findings genuinely conflict, and this has never actually been seen in people. Either way, thiotepa is serious chemotherapy with effects like low blood counts, infection risk, and nausea, so you don't want to tinker. Plain grapes in your diet are fine, but skip concentrated supplements unless your oncology team okays them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Nishikawa, M., Ariyoshi, N., Kotani, A., Ishii, I., Nakamura, H., Nakasa, H., Ida, M., Nakamura, H., Kimura, N., Kimura, M., Hasegawa, A., Kusu, F., Ohmori, S., Nakazawa, K., and Kitada, M. Effects of continuous ingestion of green tea or grape seed extra
  2. Etheridge, A. S., Black, S. R., Patel, P. R., So, J., and Mathews, J. M. An in vitro evaluation of cytochrome P450 inhibition and P-glycoprotein interaction with goldenseal, Ginkgo biloba, grape seed, milk thistle, and ginseng extracts and their constitu

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

Grape Also Interacts With Other Medications

Grape has 867 moderate, 42 minor known drug interactions in our database — the Thiotepa one above is one of them. If you take anything else, check it against the full list below.

Moderate 867 Minor 42 No known interaction 1,921 (incl. Thiotepa)
Taking anything else?

Check Another of Your Medications Against Grape

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

From our Q&A

Questions About Grape or Thiotepa

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Grape or Thiotepa, 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 Thiotepa

This page covers Grape only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Thiotepa page lists 146 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Acerola (moderate).

By severity: 3 major · 102 moderate · 41 minor.

From our pharmacist’s overview on the Thiotepa page

“Thiotepa (Thioplex, Tepadina) is chemotherapy, given for several cancers and to prepare patients for stem cell transplant, so its 146 supplement interactions make up a list to respect rather than skim. Three carry a major rating: grapefruit, St.”

Reviewed by 2 · Jul 18, 2026

Open the Thiotepa interaction page

One more smart check

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

We hold 8,053 real supplement products containing Grape, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Grape. Your product may carry other ingredients that interact with Thiotepa too, on top of Grape — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Grape and Thiotepa 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 Grape
Top 5%

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

29 days ago today
Medication Thiotepa
Steady interest

#2,093 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 Grape

What is Grape?

Grape
  • Antioxidant support
  • Heart and circulation health
  • Vein problems (such as varicose veins)
  • Eye health
  • General anti-inflammatory support

Grapes and grape products like grape seed extract contain antioxidant compounds such as resveratrol and proanthocyanidins that may support heart and blood vessel health. While the food is healthy and generally safe, the supplement evidence for treating specific conditions is mostly limited or preliminary. Talk with your pharmacist or doctor before starting a grape supplement.

Read the full Grape monograph & all interactions
Medication

About Thiotepa Injection

What Is Thiotepa Injection Used For?

Brand names: Thioplex, Tepadina

Tepadina (thiotepa) injection is used for several purposes. It treats adenocarcinoma (a type of cancer) of the breast or ovary. It is also used to control malignant effusions — abnormal fluid buildup in body cavities caused by cancer spreading to those areas. For bladder cancer, Tepadina treats superficial papillary carcinoma of the urinary bladder.

Tepadina is also used in pediatric patients with class 3 beta-thalassemia (a severe inherited blood disorder). In those patients, it is given as part of a preparative regimen — a conditioning treatment to reduce the risk of graft rejection before an allogeneic stem cell transplant (a transplant using donor stem cells), alongside the chemotherapy drugs busulfan and cyclophosphamide.

See full Thiotepa Injection drug information
Keep checking

Other Drugs & Grape

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

0Major
867Moderate
42Minor
1,920No known interaction
867 Moderate 42 Minor 1,920 No interaction
Moderate

867 interactions

Showing 60 of 867 moderate interactions — see all 867 on the Grape page.

Minor

42 interactions

No interaction 1,920 drugs checked — show the list

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

Showing the 60 most looked-up of 1,920 medications checked with no known interaction — see the full Grape list.

See the full Grape interactions page
See every supplement checked against Thiotepa, 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
Grape monograph › Uses, safety, and every drug interaction in one place Thiotepa supplement interactions › Every supplement checked against Thiotepa, ranked by severity Thiotepa Injection 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 Grape and Thiotepa Together: Common Questions

Can you take Grape with Thiotepa?
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 Grape and Thiotepa 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 Thiotepa and Grape?

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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.