Drug & supplement interaction

Vitamin C + Dactinomycin

Dactinomycin brand names: Cosmegen, Cosmegan.

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

Vitamin C has a moderate interaction with Dactinomycin. Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.

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

Vitamin C and Dactinomycin

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

Moderate

ANTITUMOR ANTIBIOTICS

Why this applies to Dactinomycin

Dactinomycin falls under ANTITUMOR ANTIBIOTICS — the group Vitamin C interacts with.

Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.
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 idea behind this one. Dactinomycin is a chemotherapy drug that partly works by creating free radicals, the unstable molecules that damage and kill cancer cells. Vitamin C is an antioxidant, which means its whole job is to mop up free radicals. So in theory, taking high-dose vitamin C could blunt some of that cancer-fighting action and make the treatment less effective.

I want to be honest with you though: this is a theoretical concern based on how these two work, not solid proof from human studies. Some researchers even think antioxidants could help. The amount of vitamin C in a normal diet is very unlikely to matter. The bigger question is concentrated supplement doses. Because this is cancer treatment where every bit of effectiveness counts, please don't start or stop any vitamin C supplement without first checking with your oncology team.

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 C Also Interacts With Other Medications

Vitamin C has 100 moderate, 106 minor known drug interactions in our database — the Dactinomycin one above is one of them. If you take anything else, check it against the full list below.

Moderate 100 Minor 106 No known interaction 2,624 (incl. Dactinomycin)
Taking anything else?

Check Another of Your Medications Against Vitamin C

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

From our Q&A

Questions About Vitamin C or Dactinomycin

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

This page covers Vitamin C only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Dactinomycin page lists 6 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Acerola (moderate), Alpha-lipoic Acid (moderate), Rose Hip (moderate), Turmeric (moderate) and Vitamin E (moderate).

By severity: 6 moderate.

From our pharmacist’s overview on the Dactinomycin page

“Every supplement flagged against dactinomycin (Cosmegen) tells the same story. This chemotherapy drug works partly by generating free radicals inside cancer cells, and each ingredient on this page is an antioxidant, vitamin C and vitamin E among them, plus turmeric and a couple of vitamin C rich botanicals.”

Reviewed by 2 · Jul 18, 2026

Open the Dactinomycin interaction page

One more smart check

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

We hold 36,382 real supplement products containing Vitamin C, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Vitamin C. Your product may carry other ingredients that interact with Dactinomycin too, on top of Vitamin C — 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 C and Dactinomycin 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 C
Most looked up

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

29 days ago today
Medication Dactinomycin
Top half

#797 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 C

What is Vitamin C?

  • Common cold and immune support
  • Antioxidant support
  • Skin health and collagen formation
  • Wound healing
  • Preventing or treating scurvy
  • Improving iron absorption

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for immune function, collagen, and acts as an antioxidant, but taking large doses doesn't prevent colds for most people and may cause stomach upset. Most people get enough from a balanced diet, so check with your pharmacist or doctor before taking high-dose supplements.

Read the full Vitamin C monograph & all interactions
Medication

About Dactinomycin

What Is Dactinomycin Used For?

Brand names: Cosmegen, Cosmegan

Dactinomycin is used to treat a range of cancers in both adults and children. These include Wilms tumor (a kidney cancer), rhabdomyosarcoma (a soft-tissue cancer), Ewing sarcoma (a bone and soft-tissue cancer), and metastatic nonseminomatous testicular cancer. For each of these, it is used as part of a multi-drug chemotherapy regimen.

It is also used in post-menarchal patients (those who have had their first period) with gestational trophoblastic neoplasia — a tumor that grows from pregnancy tissue — either alone or in combination with other drugs. In adults, it can be used as part of a regional perfusion procedure to treat locally recurrent or locoregional solid tumors.

See full Dactinomycin drug information
Keep checking

Other Drugs & Vitamin C

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

0Major
100Moderate
106Minor
2,623No known interaction
100 Moderate 106 Minor 2,623 No interaction
Moderate

100 interactions

Showing 60 of 100 moderate interactions — see all 100 on the Vitamin C page.

Minor

106 interactions

Showing 60 of 106 minor interactions — see all 106 on the Vitamin C page.

No interaction 2,623 drugs checked — show the list

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

Showing the 60 most looked-up of 2,623 medications checked with no known interaction — see the full Vitamin C list.

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

Can you take Vitamin C with Dactinomycin?
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 Vitamin C and Dactinomycin 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 Dactinomycin and Vitamin C?

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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.