Drug & supplement interaction

Evening Primrose + Treprostinil (IV)

Treprostinil (IV) brand name: Remodulin.

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

Evening Primrose has a moderate interaction with Treprostinil (IV). Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.

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

Evening Primrose and Treprostinil (IV)

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

Moderate

ANTICOAGULANT/ANTIPLATELET DRUGS

Why this applies to Treprostinil (IV)

Treprostinil (IV) falls under ANTICOAGULANT/ANTIPLATELET DRUGS — the group Evening Primrose interacts with.

Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Evening primrose oil contains gamma linolenic acid (GLA). There is preliminary clinical evidence that GLA can reduce platelet aggregation and prolong bleeding time.
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 situation with treprostinil (Remodulin) and evening primrose oil. Treprostinil itself is a powerful medication that, among other things, relaxes blood vessels and can mildly reduce how well platelets clump together. Evening primrose oil contains GLA, which some early studies suggest may also slightly thin the blood and lengthen bleeding time. Stack those two together and, in theory, you could nudge your bleeding risk a little higher.

I want to be honest about how soft this evidence is. It's mostly theoretical and based on pharmacology, not strong human trials. Still, since Remodulin is used for a serious condition and is given IV, I'd play it safe. Watch for things like easy bruising, nosebleeds, or bleeding gums, and check with your doctor or pharmacist before adding evening primrose.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Guivernau M, Meza N, Barja P, Roman O. Clinical and experimental study on the long-term effect of dietary gamma-linolenic acid on plasma lipids, platelet aggregation, thromboxane formation, and prostacyclin production. Prostaglandins Leukot Essent Fatty A 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

Evening Primrose Also Interacts With Other Medications

Evening Primrose has 147 moderate, 85 minor known drug interactions in our database — the Treprostinil (IV) one above is one of them. If you take anything else, check it against the full list below.

Moderate 147 Minor 85 No known interaction 2,598 (incl. Treprostinil (IV))
Taking anything else?

Check Another of Your Medications Against Evening Primrose

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

Everything else you take

See Every Supplement That Interacts With Treprostinil (IV)

This page covers Evening Primrose only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Treprostinil (IV) page lists 212 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: American Mistletoe (major), Danshen (major), Piracetam (major), Aconite (moderate) and African Wild Potato (moderate).

By severity: 3 major · 191 moderate · 18 minor.

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

“Bleeding risk is the thread running through nearly every supplement flagged for treprostinil (Remodulin), the IV therapy for pulmonary arterial hypertension. The drug itself discourages platelets from clumping, so the overwhelming majority of these ingredients could push that tendency further, and I would not add anything from this pag…”

Reviewed by 2 · Jul 18, 2026

Open the Treprostinil (IV) interaction page

One more smart check

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

We hold 98 real supplement products containing Evening Primrose, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Evening Primrose. Your product may carry other ingredients that interact with Treprostinil (IV) too, on top of Evening Primrose — 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 Evening Primrose and Treprostinil (IV) 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 Evening Primrose
Top half

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

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

#626 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 Evening Primrose

What is Evening Primrose?

Evening Primrose
  • Eczema and skin health
  • PMS symptoms
  • Breast pain (mastalgia)
  • Menopause symptoms
  • Inflammation
  • Diabetic nerve pain

Evening primrose oil is a seed oil rich in gamma-linolenic acid (GLA), an omega-6 fatty acid, that is popularly used for skin conditions, PMS, and breast pain. The evidence behind most of these uses is mixed or weak, and it is not proven to be a reliable treatment for any condition. It is generally well tolerated for short-term use, but talk to your pharmacist or doctor before starting it, especially if you are pregnant or have a bleeding disorder.

Read the full Evening Primrose monograph & all interactions
Medication

About Treprostinil Injection

What Is Treprostinil Injection Used For?

Brand name: Remodulin

Treprostinil injection is used to treat pulmonary arterial hypertension (PAH, WHO Group 1) — high blood pressure in the arteries that supply the lungs. It works to reduce the symptoms that make exercise difficult. Clinical studies included patients with moderate-to-severe PAH symptoms (NYHA Class II–IV) due to idiopathic or heritable PAH, PAH related to congenital heart defects, and PAH related to connective tissue diseases.

It is also used for PAH patients who need to transition off epoprostenol — a related medication — to slow the worsening of their condition during that switch. The risks and benefits of the transition should be carefully discussed with a specialist before starting.

See full Treprostinil Injection drug information
Keep checking

Other Drugs & Evening Primrose

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

0Major
147Moderate
85Minor
2,597No known interaction
147 Moderate 85 Minor 2,597 No interaction
Moderate

147 interactions

Showing 60 of 147 moderate interactions — see all 147 on the Evening Primrose page.

Minor

85 interactions

Showing 60 of 85 minor interactions — see all 85 on the Evening Primrose page.

No interaction 2,597 drugs checked — show the list

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

Showing the 60 most looked-up of 2,597 medications checked with no known interaction — see the full Evening Primrose list.

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

Can you take Evening Primrose with Treprostinil (IV)?
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 Evening Primrose and Treprostinil (IV) 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 Treprostinil (IV) and Evening Primrose?

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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.