Drug & supplement interaction

Coenzyme Q10 + Thiotepa

Thiotepa brand names: Thioplex, Tepadina.

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

Coenzyme Q10 has a moderate interaction with Thiotepa. Coenzyme Q10 has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals.

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

Coenzyme Q10 and Thiotepa

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

Moderate

ALKYLATING AGENTS

Why this applies to Thiotepa

Thiotepa falls under ALKYLATING AGENTS — the group Coenzyme Q10 interacts with.

Coenzyme Q10 has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals.
Theoretically, antioxidants such as coenzyme Q10 might protect tumor cells from chemotherapeutic agents that work by inducing oxidative stress, such as alkylating agents (e.g., cyclophosphamide) and radiation therapy. The clinical importance of this interaction is unknown.
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 concern with pairing CoQ10 and Thiotepa. Thiotepa is a chemotherapy drug (an alkylating agent), and part of how some of these treatments hurt cancer cells is by creating oxidative stress, basically harmful free radicals that damage the cells. CoQ10 is an antioxidant, so the worry on paper is that it could mop up some of those free radicals and, in theory, shield tumor cells and make the chemo work a little less well.

I want to be honest about the strength of this, though. This is a theoretical concern based on how the drugs work, not on solid human studies, so the real-world importance is genuinely unknown. Because Thiotepa is serious cancer treatment, please don't add or stop CoQ10 on your own. Run it by your oncologist or pharmacist first so nothing undercuts your therapy.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Portakal O, Ozkaya O, Erden Inal M, et al. Coenzyme Q10 concentrations and antioxidant status in tissues of breast cancer patients. Clin Biochem 2000;33:279-84. PubMed
  2. Lund EL, Quistorff B, Spang-Thomsen M, Kristjansen PE. Effect of radiation therapy on small-cell lung cancer is reduced by ubiquinone intake. Folia Microbiol (Praha) 1998;43:505-6. 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

Coenzyme Q10 Also Interacts With Other Medications

Coenzyme Q10 has 25 moderate, 172 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 25 Minor 172 No known interaction 2,633 (incl. Thiotepa)
Taking anything else?

Check Another of Your Medications Against Coenzyme Q10

Covers the 2,830 medications we’ve checked against Coenzyme Q10. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Thiotepa

This page covers Coenzyme Q10 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 Coenzyme Q10 as Part of a Dietary Supplement Product? Check It for Interactions

We hold 6,926 real supplement products containing Coenzyme Q10, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Coenzyme Q10. Your product may carry other ingredients that interact with Thiotepa too, on top of Coenzyme Q10 — 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 Coenzyme Q10 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 Coenzyme Q10
Top 5%

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

29 days ago today
Medication Thiotepa
Steady interest

#1,995 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 Coenzyme Q10

What is Coenzyme Q10?

  • Heart health
  • Statin-related muscle aches
  • Migraine prevention
  • Energy and fatigue
  • Aging and antioxidant support

CoQ10 is a vitamin-like substance your body makes naturally that helps cells produce energy and acts as an antioxidant. It is generally well tolerated and is most studied for heart conditions, statin-related muscle symptoms, and migraine prevention, though the strength of the evidence varies. Talk with your pharmacist or doctor before starting it, especially if you take heart or blood pressure medicines.

Read the full Coenzyme Q10 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 & Coenzyme Q10

Browse every other medication we’ve checked against Coenzyme Q10 — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
25Moderate
172Minor
2,632No known interaction
25 Moderate 172 Minor 2,632 No interaction
Moderate

25 interactions

Minor

172 interactions

Showing 60 of 172 minor interactions — see all 172 on the Coenzyme Q10 page.

No interaction 2,632 drugs checked — show the list

We also checked Coenzyme Q10 against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,632 medications checked with no known interaction — see the full Coenzyme Q10 list.

See the full Coenzyme Q10 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
Coenzyme Q10 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 Coenzyme Q10 and Thiotepa Together: Common Questions

Can you take Coenzyme Q10 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 Coenzyme Q10 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 Coenzyme Q10?

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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.