Drug & supplement interaction

Syrian Rue + Tamoxifen Citrate

Tamoxifen Citrate brand names: Nolvadex, Soltamox.

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

Tamoxifen Citrate falls into 3 drug categories that Syrian Rue can interact with; the most serious is rated moderate. Theoretically, Syrian rue might increase the levels and clinical effects of drugs metabolized by CYP2D6.

Read the full interaction report
SeverityModerate
LikelihoodProbable
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Syrian Rue and Tamoxifen Citrate

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Syrian Rue interacts with whole categories of medication. Tamoxifen Citrate falls into 3 of those categories, so it can interact with Syrian Rue in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

1 of 3

Why this applies to Tamoxifen Citrate

Tamoxifen Citrate falls under CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES — the group Syrian Rue interacts with.

Theoretically, Syrian rue might increase the levels and clinical effects of drugs metabolized by CYP2D6.
Syrian rue contains beta-carboline alkaloids, including harmine, harmaline, harmalol, harmol, and harmane. In vitro research suggests that these beta-carboline alkaloids can inhibit CYP2D6 enzymes.
Severity Moderate Likelihood Probable Evidence D

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the wrinkle with tamoxifen: it's actually a prodrug. Your body has to convert it into its active form (called endoxifen), and the enzyme that does most of that heavy lifting is CYP2D6. So tamoxifen needs that enzyme working well to do its job against breast cancer.

Syrian Rue contains compounds that may block CYP2D6, at least based on lab studies. If that happens in a person, you'd make less of the active endoxifen, which could mean tamoxifen works less effectively. That's a real concern, since this is a medicine you're counting on. To be fair, this interaction is theoretical and hasn't been proven in people, but given the stakes I'd play it safe. Please check with your oncologist or pharmacist before using Syrian Rue.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zhao, T., He, Y. Q., Wang, J., Ding, K. M., Wang, C. H., and Wang, Z. T. Inhibition of human cytochrome P450 enzymes 3A4 and 2D6 by β-carboline alkaloids, harmine derivatives. Phytother Res 2011;25(11):1671-1677.
Moderate

HEPATOTOXIC DRUGS

2 of 3

Tamoxifen Citrate also falls under HEPATOTOXIC DRUGS.

Theoretically, high doses of Syrian rue might increase the risk of liver damage when taken with hepatotoxic drugs.
Cases of hepatotoxicity and hepatic failure have been reported in patients who ingested a large quantity (up to 100 grams) of Syrian rue seeds.
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 when you pair these two: tamoxifen is processed by your liver and can occasionally stress it. Syrian Rue, especially in large amounts (we're talking cases where people swallowed huge quantities of the seeds, up to 100 grams), has been linked to liver injury on its own. Put them together and you may, in theory, add more strain on the liver than either would alone.

I want to be honest with you: this is a theoretical caution based on how these substances behave, not on solid studies in people taking both. Still, watch for warning signs like yellowing of the skin or eyes, dark urine, belly pain, or unusual tiredness. Please check with your pharmacist or doctor before combining them, and don't change your tamoxifen on your own.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Yuruktumen, A., Karaduman, S., Bengi, F., and Fowler, J. Syrian rue tea: a recipe for disaster. Clin Toxicol (Phila) 2008;46(8):749-752. PubMed
  2. Berdai MA, Labib S, Harandou M. Peganum harmala L. Intoxication in a Pregnant Woman. Case Rep Emerg Med 2014;2014:783236.
  3. Ghizlane EA, Manal M, Ines HA, et al. Fatal poisoning of pregnant women by peganum harmala L.: a case reports. Ann Med Surg (Lond) 2021;68:102649. PubMed
  4. Durmaz Çelik N, Ger Akarsu F, Ozkan S, Özdemir AÖ, Aykac Ö, Memmedova F. Herbal teas can be harmful: a case of Peganum harmala induced coma in a patient with Parkinson's disease. Neurocase 2021;27(2):117-119.
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

3 of 3

Tamoxifen Citrate also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, Syrian rue might increase the levels and clinical effects of drugs metabolized by CYP3A4.
Syrian rue contains beta-carboline alkaloids, including harmine, harmol, and harmane. In vitro research suggests that these beta-carboline alkaloids competitively inhibit CYP3A4 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 the thing about tamoxifen: your body has to convert it into its active form (called endoxifen) before it can do its job of fighting breast cancer. A few liver enzymes handle that, and CYP3A4 is one of them. Lab studies suggest the harmala alkaloids in Syrian Rue can block CYP3A4. In theory, slowing this enzyme could shift how tamoxifen is processed, though the effect on its real-world benefit is hard to predict.

I want to be honest that this is a theoretical concern based on test-tube data, not proven in people. Even so, with a cancer medicine you don't want to gamble on. Syrian Rue also carries its own toxicity risks, so please check with your oncologist or pharmacist before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zhao, T., He, Y. Q., Wang, J., Ding, K. M., Wang, C. H., and Wang, Z. T. Inhibition of human cytochrome P450 enzymes 3A4 and 2D6 by β-carboline alkaloids, harmine derivatives. Phytother Res 2011;25(11):1671-1677.

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

Syrian Rue Also Interacts With Other Medications

Syrian Rue has 1,121 moderate known drug interactions in our database — the Tamoxifen Citrate one above is among them. If you take anything else, check it against the full list below.

Moderate 1,121 No known interaction 1,709 (incl. Tamoxifen Citrate)
Taking anything else?

Check Another of Your Medications Against Syrian Rue

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

From our Q&A

Questions About Syrian Rue or Tamoxifen Citrate

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

This page covers Syrian Rue only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Tamoxifen Citrate page lists 210 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 166 moderate · 33 minor.

From our pharmacist’s overview on the Tamoxifen Citrate page

“Tamoxifen (Nolvadex, Soltamox) often stands between a breast cancer patient and a recurrence, so the stakes on this page run higher than usual. Eleven of the 210 supplements and herbs on file carry a major rating, and those eleven deserve your attention ahead of everything else.”

Reviewed by 2 · Jul 18, 2026

Open the Tamoxifen Citrate interaction page

How much people look this up

Where Syrian Rue and Tamoxifen Citrate 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 Syrian Rue
Steady interest

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

29 days ago today
Medication Tamoxifen Citrate
Top 10%

#174 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 Syrian Rue

What is Syrian Rue?

  • Traditional remedy for digestive complaints
  • Used as a sedative or for mood
  • Antimicrobial and antiparasitic folk use
  • Used as a dye and incense
  • Recreational psychoactive use

Syrian Rue (Peganum harmala) is a traditional plant whose seeds contain potent compounds called harmala alkaloids, including MAO-inhibiting harmine and harmaline. There is little reliable human evidence that it safely treats any condition, and it carries real risks of toxicity, so it is not recommended for self-treatment. Talk to a pharmacist or doctor before considering it.

Read the full Syrian Rue monograph & all interactions
Medication

About Tamoxifen

What Is Tamoxifen Used For?

Brand names: Nolvadex, Soltamox

Tamoxifen is used to treat metastatic breast cancer (breast cancer that has spread) in both women and men, and as adjuvant (after-surgery) therapy for early-stage breast cancer in women. It also reduces the occurrence of cancer in the opposite breast when used as adjuvant therapy.

In women with ductal carcinoma in situ (DCIS) — a very early, non-invasive form of breast cancer — tamoxifen is used after breast surgery and radiation to reduce the risk of developing invasive breast cancer. It is also approved to reduce the incidence of breast cancer in women who are at high risk but have not yet been diagnosed. Soltamox (oral solution) is specifically indicated for all of these uses in adult patients.

See full Tamoxifen drug information
Keep checking

Other Drugs & Syrian Rue

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

0Major
1,121Moderate
0Minor
1,708No known interaction
1,121 Moderate 1,708 No interaction
Moderate

1,121 interactions

Showing 60 of 1,121 moderate interactions — see all 1,121 on the Syrian Rue page.

No interaction 1,708 drugs checked — show the list

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

Showing the 60 most looked-up of 1,708 medications checked with no known interaction — see the full Syrian Rue list.

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

Can you take Syrian Rue with Tamoxifen Citrate?
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 3 interactions listed for Syrian Rue and Tamoxifen Citrate?
Tamoxifen Citrate belongs to more than one drug category, and Syrian Rue 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 Syrian Rue and Tamoxifen Citrate 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 Tamoxifen Citrate and Syrian Rue?

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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.