Drug & supplement interaction

Vitamin E + Cyclophosphamide

Cyclophosphamide brand names: Cytoxan, Neosar.

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

Cyclophosphamide falls into 2 drug categories that Vitamin E can interact with; the most serious is rated moderate. Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Vitamin E and Cyclophosphamide

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Vitamin E interacts with whole categories of medication. Cyclophosphamide falls into 2 of those categories, so it can interact with Vitamin E in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 2

Why this applies to Cyclophosphamide

Cyclophosphamide falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Vitamin E interacts with.

Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.
Vitamin E appears to bind with the nuclear receptor, pregnane X receptor (PXR), which results in increased expression of CYP3A4. Although the clinical significance of this is not known, use caution when considering concomitant use of vitamin E and other drugs affected by these enzymes.
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 a wrinkle worth knowing about. Cyclophosphamide is a prodrug, meaning it shows up inactive and your liver enzymes (including CYP3A4) have to switch it on before it can fight cancer. The theory on file is that high-dose vitamin E may gently speed up CYP3A4. With most drugs, speeding up that enzyme would lower their levels, but because cyclophosphamide needs that enzyme to activate, faster processing could actually nudge more drug into its active form.

I'll be honest, this is theoretical and based on how things work in the lab, not real patient outcomes, so don't panic. Still, with a chemotherapy drug, even small shifts matter. Please loop in your oncology team or pharmacist before adding any vitamin E supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Landes N, Pfluger P, Kluth D, et al. Vitamin E activates gene expression via the pregnane X receptor. Biochem Pharmacol 2003;65:269-73. . PubMed
  2. Brigelius-Flohe R. Vitamin E and drug metabolism. Biochem Biophys Res Commun 2003;305:737-40. PubMed
Moderate

ALKYLATING AGENTS

2 of 2

Cyclophosphamide also falls under ALKYLATING AGENTS.

Theoretically, antioxidant effects of vitamin E might reduce the effectiveness of alkylating agents.
There's concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa. However, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that might interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin E have on chemotherapy. Advise patients to consult their oncologist before using vitamin E supplements, especially in high doses.
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. Cyclophosphamide is part of a group of chemo drugs that fight cancer partly by creating free radicals, the very unstable molecules that vitamin E is designed to mop up. So on paper, taking high-dose vitamin E (a strong antioxidant) might blunt how well your chemo works. That said, this is purely theoretical. Some researchers actually wonder if antioxidants could help chemo work better, and good human evidence simply doesn't exist yet either way.

So I wouldn't panic, but I also wouldn't add vitamin E supplements on your own during treatment. The amount in a normal diet isn't the concern; concentrated supplement doses are. Please loop in your oncologist before taking any, since they're steering your cancer care.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Labriola D, Livingston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology 1999;13:1003-8.
  2. Prasad KN. Rationale for using high-dose multiple dietary antioxidants as an adjunct to radiation therapy and chemotherapy. J Nutr 2004;134:3182S-3S. PubMed
  3. Conklin KA. Cancer chemotherapy and antioxidants. J Nutr 2004;134:3201S-3204S. 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

Vitamin E Also Interacts With Other Medications

Vitamin E has 762 moderate, 1 minor known drug interactions in our database — the Cyclophosphamide one above is among them. If you take anything else, check it against the full list below.

Moderate 762 Minor 1 No known interaction 2,067 (incl. Cyclophosphamide)
Taking anything else?

Check Another of Your Medications Against Vitamin E

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

Everything else you take

See Every Supplement That Interacts With Cyclophosphamide

This page covers Vitamin E only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cyclophosphamide page lists 220 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 176 moderate · 38 minor.

Open the Cyclophosphamide interaction page

One more smart check

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

We hold 22,182 real supplement products containing Vitamin E, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin E. Your product may carry other ingredients that interact with Cyclophosphamide too, on top of Vitamin E — 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 Vitamin E and Cyclophosphamide 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 Vitamin E
Top 10

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

29 days ago today
Medication Cyclophosphamide
Steady interest

#1,750 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 Vitamin E

What is Vitamin E?

Vitamin E
  • General antioxidant support
  • Skin and hair care
  • Heart health
  • Eye health (age-related conditions)
  • Immune support

Vitamin E is an essential fat-soluble vitamin and antioxidant that most people get in adequate amounts from a normal diet. Supplements can help correct a true deficiency, but high-dose vitamin E has not been clearly proven to prevent heart disease or cancer and may carry risks. Talk to your pharmacist or doctor before taking high doses.

Read the full Vitamin E monograph & all interactions
Medication

About Cyclophosphamide

What Is Cyclophosphamide Used For?

Brand names: Cytoxan, Neosar

Cyclophosphamide is used to treat many types of cancer in adults and children, including malignant lymphomas (such as Hodgkin's disease and Burkitt's lymphoma), multiple myeloma, several forms of leukemia, breast cancer, ovarian cancer, neuroblastoma, retinoblastoma, and advanced mycosis fungoides (a type of skin lymphoma). It is often given alongside other chemotherapy drugs rather than on its own.

Oral and injectable powder formulations (but not the Cyclophosphamide Injection solution concentrate) are also approved for minimal change nephrotic syndrome — a kidney condition — in children who have not responded well to, or cannot tolerate, steroid therapy. The injectable solution concentrate is approved for adult patients only due to its alcohol content, and is not approved for use in children.

See full Cyclophosphamide drug information
Keep checking

Other Drugs & Vitamin E

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

0Major
762Moderate
1Minor
2,066No known interaction
762 Moderate 1 Minor 2,066 No interaction
Moderate

762 interactions

Showing 60 of 762 moderate interactions — see all 762 on the Vitamin E page.

Minor

1 interaction

No interaction 2,066 drugs checked — show the list

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

Showing the 60 most looked-up of 2,066 medications checked with no known interaction — see the full Vitamin E list.

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

Can you take Vitamin E with Cyclophosphamide?
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.
Why are there 2 interactions listed for Vitamin E and Cyclophosphamide?
Cyclophosphamide belongs to more than one drug category, and Vitamin E interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Vitamin E and Cyclophosphamide 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 Cyclophosphamide and Vitamin E?

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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.