Drug & supplement interaction

Fennel + Treprostinil (Oral)

Treprostinil (Oral) brand names: Remodulin, Orenitram.

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

Fennel has a moderate interaction with Treprostinil (Oral). Theoretically, fennel might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.

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

Fennel and Treprostinil (Oral)

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

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Treprostinil (Oral)

Treprostinil (Oral) falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Fennel interacts with.

Theoretically, fennel might increase the risk of bleeding when used with antiplatelet or anticoagulant drugs.

Animal research suggests that fennel oil has antithrombotic and antiplatelet effects.
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 short version: oral treprostinil (Remodulin) already nudges your platelets toward not sticking together, which can slightly raise your odds of bruising or bleeding on its own. Fennel may do a little of the same thing. In lab and animal studies, fennel oil showed mild antiplatelet and clot-slowing activity, so stacking the two could, in theory, add up to a bit more bleeding risk.

Keep this in perspective. This is a theoretical concern based only on animal and test-tube work, not on people, and a sprinkle of fennel in your cooking is very unlikely to matter. Concentrated fennel capsules or the essential oil are the bigger question mark. Watch for easy bruising, nosebleeds, or bleeding that won't quit, and check with your pharmacist or doctor before adding a fennel supplement.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Tognolini, M., Ballabeni, V., Bertoni, S., Bruni, R., Impicciatore, M., and Barocelli, E. Protective effect of Foeniculum vulgare essential oil and anethole in an experimental model of thrombosis. Pharmacol.Res 2007;56(3):254-260. PubMed
  2. Tognolini, M., Barocelli, E., Ballabeni, V., Bruni, R., Bianchi, A., Chiavarini, M., and Impicciatore, M. Comparative screening of plant essential oils: phenylpropanoid moiety as basic core for antiplatelet activity. Life Sci. 2-23-2006;78(13):1419-1432. 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

Fennel Also Interacts With Other Medications

Fennel has 739 moderate known drug interactions in our database — the Treprostinil (Oral) one above is one of them. If you take anything else, check it against the full list below.

Moderate 739 No known interaction 2,091 (incl. Treprostinil (Oral))
Taking anything else?

Check Another of Your Medications Against Fennel

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

From our Q&A

Questions About Fennel or Treprostinil (Oral)

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Fennel or Treprostinil (Oral), 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 Treprostinil (Oral)

This page covers Fennel only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Treprostinil (Oral) page lists 291 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Danshen (major) and Piracetam (major).

By severity: 6 major · 258 moderate · 27 minor.

From our pharmacist’s overview on the Treprostinil (Oral) page

“With treprostinil (Orenitram), a medicine that opens narrowed lung arteries in pulmonary arterial hypertension, supplements deserve more scrutiny than usual. The drug widens blood vessels and dampens platelet clumping, and nearly everything on this list leans on one of those two levers.”

Reviewed by 2 · Jul 18, 2026

Open the Treprostinil (Oral) interaction page

One more smart check

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

We hold 2,219 real supplement products containing Fennel, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Fennel. Your product may carry other ingredients that interact with Treprostinil (Oral) too, on top of Fennel — 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 Fennel and Treprostinil (Oral) 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 Fennel
Top 10%

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

29 days ago today
Medication Treprostinil (Oral)
Top 25%

#599 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 Fennel

What is Fennel?

Fennel
  • Digestive upset and bloating
  • Infant colic
  • Menstrual cramps
  • Cough and respiratory complaints
  • Breast milk support (traditional)

Fennel is a Mediterranean herb widely used as a food and spice, and traditionally taken for digestive complaints, colic, and menstrual cramps. Some small studies suggest possible benefit for certain stomach and menstrual symptoms, but the evidence is limited. It is generally well tolerated in food amounts, but concentrated supplements and the essential oil should be used with caution and after checking with your pharmacist or doctor.

Read the full Fennel monograph & all interactions
Medication

About Treprostinil

What Is Treprostinil Used For?

Brand names: Remodulin, Orenitram

Treprostinil treats pulmonary arterial hypertension (PAH; WHO Group 1) — high blood pressure in the arteries of the lungs. Depending on the product and route, it is used to improve exercise ability, delay disease progression, or reduce symptoms tied to physical activity. Remodulin and treprostinil injection products are also indicated for patients who need to transition away from another PAH medicine called epoprostenol.

Tyvaso, Tyvaso DPI, and Yutrepia (inhaled forms) are additionally approved to treat pulmonary hypertension associated with interstitial lung disease (PH-ILD; WHO Group 3) — lung-pressure problems caused by scarring or inflammation in the lung tissue itself. Orenitram (extended-release oral tablet) is specifically indicated to delay disease progression and improve exercise capacity in PAH.

See full Treprostinil drug information
Keep checking

Other Drugs & Fennel

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

0Major
739Moderate
0Minor
2,090No known interaction
739 Moderate 2,090 No interaction
Moderate

739 interactions

Showing 60 of 739 moderate interactions — see all 739 on the Fennel page.

No interaction 2,090 drugs checked — show the list

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

Showing the 60 most looked-up of 2,090 medications checked with no known interaction — see the full Fennel list.

See the full Fennel interactions page
See every supplement checked against Treprostinil (Oral), 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
Fennel monograph › Uses, safety, and every drug interaction in one place Treprostinil (Oral) supplement interactions › Every supplement checked against Treprostinil (Oral), ranked by severity Treprostinil 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 Fennel and Treprostinil (Oral) Together: Common Questions

Can you take Fennel with Treprostinil (Oral)?
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 Fennel and Treprostinil (Oral) 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

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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.