Drug & supplement interaction

Panax Ginseng + Letrozole

Letrozole brand name: Femara.

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

Panax Ginseng has a moderate interaction with Letrozole. Theoretically, Panax ginseng might increase or decrease levels of drugs metabolized by CYP3A4.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceB
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Panax Ginseng and Letrozole

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

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Letrozole

Letrozole falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Panax Ginseng interacts with.

Theoretically, Panax ginseng might increase or decrease levels of drugs metabolized by CYP3A4.
Panax ginseng may affect the clearance of drugs metabolized by CYP3A4. One such drug is imatinib. Inhibition of CYP3A4 was believed to be responsible for a case of imatinib-induced hepatotoxicity. In contrast, Panax ginseng has been shown to increase the clearance of midazolam, another drug metabolized by CYP3A4. Clinical research shows that Panax ginseng can reduce midazolam area under the curve by 44%, maximum plasma concentration by 26%, and time to reach maximum plasma concentration by 29%. Midazolam metabolism was also increased in animals given Panax ginseng. Until more is known, use Panax ginseng cautiously in combination with CYP3A4 substrates.
Severity Moderate Likelihood Possible Evidence B

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 situation with Femara (letrozole) and Panax ginseng. Your body relies on a liver enzyme called CYP3A4 to help break letrozole down, and ginseng can nudge that enzyme in either direction. In some studies it sped the enzyme up (which could lower letrozole levels and, in theory, make it work less well at controlling your breast cancer), while in other cases it slowed the enzyme down (which could let letrozole build up and bring on more of its usual effects like hot flashes, joint and bone aches, tiredness, or headache).

To be honest, this is mostly theoretical and based on limited research, not strong studies on letrozole itself. Letrozole is not a prodrug, so it doesn't get flipped the other way. Because keeping your cancer treatment reliable really matters, please check with your pharmacist or oncologist before adding ginseng.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Malati CY, Robertson SM, Hunt JD, Chairez C, Alfaro RM, Kovacs JA, Penzak SR. Influence of Panax ginseng on cytochrome P450 (CYP)3A and P-glycoprotein (P-gp) activity in healthy participants. J Clin Pharmacol 2012;52(6):932-9.
  2. Bilgi N, Bell K, Ananthakrishnan AN, Atallah E. Imatinib and Panax ginseng: a potential interaction resulting in liver toxicity. Ann Pharmacother 2010;44(5):926-8.
  3. Kim Y, Jo JJ, Cho P, et al. Characterization of red ginseng-drug interaction by CYP3A activity increased in high dose administration in mice. Biopharm Drug Dispos. 2020;41(7):295-306. 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

Panax Ginseng Also Interacts With Other Medications

Panax Ginseng has 1,129 moderate known drug interactions in our database — the Letrozole one above is one of them. If you take anything else, check it against the full list below.

Moderate 1,129 No known interaction 1,701 (incl. Letrozole)
Taking anything else?

Check Another of Your Medications Against Panax Ginseng

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

From our Q&A

Questions About Panax Ginseng 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 Panax Ginseng 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 Panax Ginseng 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 Panax Ginseng as Part of a Dietary Supplement Product? Check It for Interactions

We hold 517 real supplement products containing Panax Ginseng, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Panax Ginseng. Your product may carry other ingredients that interact with Letrozole too, on top of Panax Ginseng — 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 Panax Ginseng 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 Panax Ginseng
Top 25%

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

29 days ago today
Medication Letrozole
Top 5%

#48 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 Panax Ginseng

What is Panax Ginseng?

Panax Ginseng
  • Boosting energy and fighting fatigue
  • Improving mental focus and memory
  • Coping with stress (adaptogen)
  • Erectile dysfunction
  • Supporting immune health
  • Blood sugar support

Panax ginseng is a popular traditional herb used to boost energy, ease stress, and support overall wellness, though scientific evidence is mixed and mostly preliminary. It is generally well tolerated for short-term use in healthy adults, but it can cause side effects like trouble sleeping and may not be safe during pregnancy or breastfeeding. Always check with your pharmacist or doctor before starting it, especially if you have a medical condition or take other medicines.

Read the full Panax Ginseng monograph & all interactions
Medication

About Letrozole

What Is Letrozole Used For?

Brand name: Femara

Letrozole (brand name Femara) is used to treat breast cancer in postmenopausal women whose tumors are driven by estrogen. It is used in three settings: as adjuvant (after-surgery) treatment for hormone receptor positive early breast cancer; as extended adjuvant treatment for women who have already completed about five years of tamoxifen therapy; and as first- or second-line treatment for locally advanced or metastatic (spread) breast cancer.

Femara is specifically indicated for first-line treatment of hormone receptor positive or receptor-unknown locally advanced or metastatic breast cancer, and for advanced breast cancer in women whose disease has progressed after antiestrogen therapy.

See full Letrozole drug information
Keep checking

Other Drugs & Panax Ginseng

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

0Major
1,129Moderate
0Minor
1,700No known interaction
1,129 Moderate 1,700 No interaction
Moderate

1,129 interactions

Showing 60 of 1,129 moderate interactions — see all 1,129 on the Panax Ginseng page.

No interaction 1,700 drugs checked — show the list

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

Showing the 60 most looked-up of 1,700 medications checked with no known interaction — see the full Panax Ginseng list.

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

Can you take Panax Ginseng with Letrozole?
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 Panax Ginseng and Letrozole 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 Letrozole and Panax Ginseng?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.