Drug & supplement interaction

Canthaxanthin + Letrozole

Letrozole brand name: Femara.

No Known Interaction
Medically reviewed by · Updated October 2026 · Pair last verified Oct 4, 2026
The bottom line No known interaction

We found no known interaction between Canthaxanthin and Letrozole in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Canthaxanthin and Letrozole

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Letrozole and Canthaxanthin in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

Worth understanding: our licensed dataset holds no drug-interaction record for Canthaxanthin at all — not against Letrozole, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Canthaxanthin safety at a glance

Canthaxanthin overall Use caution Generally fine in small food-coloring amounts, but high-dose supplements have been linked to eye and other problems.
Pregnancy Avoid Not enough safety data; avoid supplemental doses during pregnancy.
Breastfeeding Avoid Safety while breastfeeding is unknown, so avoid supplemental use.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Letrozole and Canthaxanthin? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Canthaxanthin and Letrozole May Share a Side Effect

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Nausea Additional detail

    Canthaxanthin

    “Orally, large amounts of canthaxanthin can cause orange-brown coloration of the skin, brick-red coloration of stools, orange discoloration of plasma, discolored body secretions, diarrhea, nausea, stomach cramps, dry and itchy skin, urticaria, welts, gold and yellow crystalline deposits around the macula of the retina, and hepatitis.”

    Canthaxanthin · Natural Medicines adverse-effect record, reported in anemia.

    6 sources cited
    1. 5632. Lober CW. Canthaxanthin- the "tanning" pill. J Am Acad Dermatol 1985;13:660. PubMed
    2. 5631. Jackson R. Quick suntan pills in Canada. J Am Acad Dermatol 1981;4:233. PubMed
    3. 5634. Rock GA, Decary F, Cole RS. Orange plasma from tanning capsules. Lancet 1981;1:1419-20. PubMed
    4. 5637. Herbert V. Canthaxanthin toxicity. Am J Clin Nutr 1991;53:573-4. DOI
    5. 5635. Bluhm R, Branch R, Johnston P, Stein R. Aplastic anemia associated with canthaxanthin ingested for 'tanning' purposes. JAMA 1990;264:1141-2. DOI
    6. 5636. Harnois C, Samson J, Malenfant M, Rousseau A. Canthaxanthin retinopathy. Anatomic and funtional reversibility. Arch Ophthalmol 1989;107:538-40. DOI

    Letrozole

    Listed in the ADVERSE REACTIONS section of the FDA label for Letrozole. Read the label on DailyMed ›

Reported for Canthaxanthin but not commonly for Letrozole: stomach pain, itching, hives and liver problems.

Effects for Letrozole come from the ADVERSE REACTIONS section of its FDA label; effects for Canthaxanthin come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Overlapping uses

What Letrozole Is Prescribed For, and What Canthaxanthin Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Letrozole is a prescription medicine with approved uses on its FDA label. Canthaxanthin is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Letrozole is prescribed for: Letrozole (brand name Femara, or available as generic letrozole tablets) is used to treat breast cancer in postmenopausal women whose tumors are hormone receptor positive — meaning the cancer feeds on estrogen. It is used in several situations: as an adjuvant treatment (therapy given after primary treatment to reduce the risk of the cancer returning) for early breast cancer, and as extended adjuvant treatment for women who have already completed five years of tamoxifen therapy. Femara and letrozole tablets are also used as first-line or second-line treatment for locally advanced or metastatic (spread to other areas) breast cancer in postmenopausal women, including cases where the cancer has progressed after other anti-estrogen therapy.

Canthaxanthin has been studied for:

  • Cancer studied, not established Canthaxanthin has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Canthaxanthin for cancer

    Although there has been interest in using oral canthaxanthin for cancer, there is insufficient reliable information about the clinical effects of canthaxanthin for this purpose.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Letrozole on your own; if you are taking Canthaxanthin for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Canthaxanthin or Letrozole

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

This page covers Canthaxanthin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Letrozole page lists 142 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), 7-methoxyflavone (moderate) and Acacia Rigidula (moderate).

By severity: 3 major · 99 moderate · 40 minor.

From our pharmacist’s overview on the Letrozole page

“Letrozole (Femara) is prescribed to keep hormone-driven breast cancer from returning, so a supplement that shifts its blood level can quietly undercut treatment. Give this list of 142 ingredients genuine respect, and learn the three major entries first.”

Reviewed by 2 · Jul 18, 2026

Open the Letrozole interaction page

One more smart check

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

We hold 1 real supplement products containing Canthaxanthin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Canthaxanthin. Even though Canthaxanthin itself has no known interaction with Letrozole, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Canthaxanthin and Letrozole 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 Canthaxanthin
Steady interest

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

29 days ago today
Medication Letrozole
Top 5%

#58 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Canthaxanthin reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified October 4, 2026. The Canthaxanthin and Letrozole records this page draws on were last updated October 6, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Canthaxanthin

What is Canthaxanthin?

  • Skin coloring or 'tanning pills'
  • Food and feed coloring (e.g., to color farmed fish/poultry)
  • Antioxidant supplement
  • Erythropoietic protoporphyria (light sensitivity, historical/medical use)

Canthaxanthin is a reddish-orange carotenoid pigment used mainly as a coloring agent and in 'tanning pills.' There is little good evidence it provides health benefits, and high doses have been linked to a serious eye problem called canthaxanthin retinopathy, so the tanning-pill use is widely discouraged.

Carotenoid pigment (synthetic or from sources like the mushroom Cantharellus cinnabarinus, certain algae, and crustaceans) · Oral tablets and capsules, often marketed as 'tanning pills'; also used as a food coloring additive

An interaction check asks whether these two react with each other — it does not ask whether Canthaxanthin is a good idea for someone in your situation. Here is what our Canthaxanthin record says about it on its own.

Canthaxanthin: dosing

There is no established, recommended supplement dose of canthaxanthin for any health condition, and the high doses once used for skin coloring are not considered safe. Given the known risks at high doses, most people are better off avoiding supplemental canthaxanthin entirely.

From our Canthaxanthin monograph — the full record covers uses, side effects and every documented interaction.

Read the full Canthaxanthin monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara, or available as generic letrozole tablets) is used to treat breast cancer in postmenopausal women whose tumors are hormone receptor positive — meaning the cancer feeds on estrogen. It is used in several situations: as an adjuvant treatment (therapy given after primary treatment to reduce the risk of the cancer returning) for early breast cancer, and as extended adjuvant treatment for women who have already completed five years of tamoxifen therapy.

Femara and letrozole tablets are also used as first-line or second-line treatment for locally advanced or metastatic (spread to other areas) breast cancer in postmenopausal women, including cases where the cancer has progressed after other anti-estrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Canthaxanthin

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Canthaxanthin list.

See the full Canthaxanthin interactions page
See every supplement checked against Letrozole, ranked by severity
Evidence & sources

Canthaxanthin References

The 12 references that drive our Canthaxanthin monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Jackson R. Quick suntan pills in Canada. J Am Acad Dermatol 1981;4:233. PubMed
  2. Lober CW. Canthaxanthin- the "tanning" pill. J Am Acad Dermatol 1985;13:660. PubMed
  3. Rock GA, Decary F, Cole RS. Orange plasma from tanning capsules. Lancet 1981;1:1419-20. PubMed
  4. Bluhm R, Branch R, Johnston P, Stein R. Aplastic anemia associated with canthaxanthin ingested for 'tanning' purposes. JAMA 1990;264:1141-2. DOI
  5. Harnois C, Samson J, Malenfant M, Rousseau A. Canthaxanthin retinopathy. Anatomic and funtional reversibility. Arch Ophthalmol 1989;107:538-40. DOI
  6. Herbert V. Canthaxanthin toxicity. Am J Clin Nutr 1991;53:573-4. DOI
  7. White GL Jr, Beesley R, Thiese SM, Murdock RT. Retinal crystals and oral tanning agents. Am Fam Physician 1988;37:125-6.
  8. Chang TS, Aylward W, Clarkson JG, Gass JD. Asymmetric canthaxanthin retinopathy. Am J Ophthalmol 1995;119:801-2. PubMed
  9. Leyon H, Ros AM, Nyberg S, Algvere P. Reversibility of canthaxanthin deposits within the retina. Acta Ophthalmol (Copenh) 1990;68:607-11. PubMed
  10. Espaillat A, Aiello LP, Arrigg PG, et al. Canthaxanthine retinopathy. Arch Ophthalmol 1999;117:412-3.. PubMed
  11. Bareford, D., Cumberbatch, M., and Derrick, Tovey L. Plasma discolouration due to sun-tanning aids. Vox Sang. 1984;46(3):180-182. DOI
  12. Gunson, H. H., Merry, A. H., Britton, G., and Stratton, F. Detection of carotenoids in blood donors taking Orobronze: a cautionary note. Clin.Lab Haematol. 1984;6(3):287-292. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Canthaxanthin and Letrozole Together: Common Questions

Is it safe to take Canthaxanthin with Letrozole?
We do not list a known interaction between Canthaxanthin and Letrozole. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Canthaxanthin and Letrozole have any of the same side effects?
Yes — our sources link each of them separately to one of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Canthaxanthin and Letrozole used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Canthaxanthin in each. That is a conversation for your prescriber, especially if Letrozole is being adjusted to a target.
Does Letrozole interact with any supplements?
Yes. Letrozole has documented interactions with 142 supplements in our database — Canthaxanthin is not one of them. The Letrozole interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Canthaxanthin monograph Uses, safety profile, and every drug interaction in one place Letrozole drug information The full plain-English guide to this medication Letrozole supplement interactions Every supplement checked against Letrozole, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 12 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Letrozole and Canthaxanthin?

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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.