Drug & supplement interaction

American Mistletoe + Vardenafil

Vardenafil brand names: Levitra, Staxyn.

Major Interaction
Medically reviewed by · Updated February 2024
The bottom line Major

American Mistletoe has a major interaction with Vardenafil. American mistletoe contains phoratoxin, a compound toxic to humans that induces smooth muscle contraction and vasoconstriction, potentially increasing blood pressure and heart rate.

Read the full interaction report
SeverityMajor
LikelihoodProbable
EvidenceC
What do Severity, Likelihood & Evidence mean?
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Interaction report

American Mistletoe and Vardenafil

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

Major

Vasodilators

Why this applies to Vardenafil

Vardenafil falls under Vasodilators — the group American Mistletoe interacts with.

American mistletoe contains phoratoxin, a compound toxic to humans that induces smooth muscle contraction and vasoconstriction, potentially increasing blood pressure and heart rate. Taking dietary supplements containing American mistletoe may counteract the effects of vasodilator drugs, such as hydralazine. It is important to note that American mistletoe is uncommon in dietary supplements. More commonly, European mistletoe is used as it does not contain phoratoxin.
Severity Major Likelihood Probable Evidence C

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 short version: Vardenafil (Levitra, Staxyn) works by relaxing and widening blood vessels so more blood can flow to the penis. American mistletoe pulls in the opposite direction. Its toxin, phoratoxin, can tighten blood vessels and nudge blood pressure and heart rate upward. So in theory, mistletoe could blunt some of what vardenafil is trying to do and add stress to your heart and circulation.

The honest truth is the evidence here is thin and mostly from lab and animal studies, so I wouldn't lose sleep over it. The bigger point is that American mistletoe is genuinely toxic and isn't something I'd recommend taking at all. If you're considering any mistletoe product, please run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction

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

American Mistletoe Also Interacts With Other Medications

American Mistletoe has 189 major, known drug interactions in our database — the Vardenafil one above is one of them. If you take anything else, check it against the full list below.

Major 189 No known interaction 2,641 (incl. Vardenafil)
Taking anything else?

Check Another of Your Medications Against American Mistletoe

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

From our Q&A

Questions About American Mistletoe or Vardenafil

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

This page covers American Mistletoe only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Vardenafil page lists 144 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), Hawthorn (major), St. John's Wort (major) and Acacia Rigidula (moderate).

By severity: 5 major · 98 moderate · 41 minor.

From our pharmacist’s overview on the Vardenafil page

“Vardenafil (Levitra, Staxyn), the erectile dysfunction pill, is broken down by a single liver enzyme, CYP3A4, and that one fact shapes most of this page. Supplements that block the enzyme, grapefruit being the best documented, can push vardenafil levels up and intensify its side effects, while St.”

Reviewed by 2 · Jul 18, 2026

Open the Vardenafil interaction page

How much people look this up

Where American Mistletoe and Vardenafil 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 American Mistletoe
Steady interest

#1,249 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Vardenafil
Top half

#1,082 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 American Mistletoe

What is American Mistletoe?

American Mistletoe
  • Traditional folk remedies
  • Digestive complaints
  • Decorative holiday plant

American mistletoe is a parasitic plant that is best known as a holiday decoration, not a proven medicine. It contains toxins that can harm the heart, gut, and blood vessels, and it has little reliable evidence to support any health use. We do not recommend taking it, and all parts should be kept away from children and pets.

Read the full American Mistletoe monograph & all interactions
Medication

About Vardenafil

What Is Vardenafil Used For?

Brand names: Levitra, Staxyn

Vardenafil tablets and orally disintegrating tablets are both indicated for the treatment of erectile dysfunction — difficulty getting or keeping an erection firm enough for sex.

Sexual stimulation is required for vardenafil to work. It does not cause an erection on its own.

See full Vardenafil drug information
Keep checking

Other Drugs & American Mistletoe

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

189Major
0Moderate
0Minor
2,640No known interaction
189 Major 2,640 No interaction
Major

189 interactions

Showing 60 of 189 major interactions — see all 189 on the American Mistletoe page.

No interaction 2,640 drugs checked — show the list

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

Showing the 60 most looked-up of 2,640 medications checked with no known interaction — see the full American Mistletoe list.

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

Can you take American Mistletoe with Vardenafil?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the American Mistletoe and Vardenafil interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

Still Have a Question About Vardenafil and American Mistletoe?

Our pharmacists answer your medication & supplement questions — free.

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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.