Drug & supplement interaction

Evening Primrose + Torsemide

Torsemide brand names: Demadex, Soaanz.

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

Evening Primrose has a minor interaction with Torsemide. Theoretically, evening primrose may increase the levels and clinical effects of CYP2C9 substrates.

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

Evening Primrose and Torsemide

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

Minor

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

Why this applies to Torsemide

Torsemide falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Evening Primrose interacts with.

Theoretically, evening primrose may increase the levels and clinical effects of CYP2C9 substrates.
In vitro research shows that linoleic acid, a constituent of evening primrose oil, inhibits CYP2C9.
Severity Minor 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 gist with these two together. Your body uses a liver enzyme called CYP2C9 to help clear torsemide, your water pill. Lab studies (in test tubes, not in people) suggest a fatty acid in evening primrose oil may slow that enzyme down a bit. In theory, that could let a little more torsemide hang around than usual, nudging its effects up.

If that happened, you might notice more of torsemide's usual actions: extra trips to the bathroom, lightheadedness, dehydration, or a dip in blood pressure. That said, this is theoretical and rated minor, so for most folks it likely won't cause trouble. Still, it's worth a quick chat with your pharmacist or doctor before adding evening primrose, especially if you watch your blood pressure closely.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zou L, Harkey MR, and Henderson GL. Effects of herbal components on cDNA-expressed cytochrome P450 enzyme catalytic activity. Life Sci 8-16-2002;71(13):1579-1589. 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 148 moderate, 84 minor known drug interactions in our database — the Torsemide one above is one of them. If you take anything else, check it against the full list below.

Moderate 148 Minor 84 No known interaction 2,598 (incl. Torsemide)
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 Torsemide

This page covers Evening Primrose only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Torsemide page lists 251 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), Apple (major) and Grapefruit (major).

By severity: 10 major · 204 moderate · 37 minor.

From our pharmacist’s overview on the Torsemide page

“Torsemide (Demadex, Soaanz) is a water pill for fluid buildup from heart failure, kidney disease, or liver disease, and its supplement list earns genuine caution, with 10 of the 251 flagged ingredients rated major. Most entries either pile onto its blood-pressure-lowering effect or add extra diuretic action that can pull your potassium…”

Reviewed by 2 · Jul 18, 2026

Open the Torsemide 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 Torsemide 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 Torsemide 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

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

29 days ago today
Medication Torsemide
Steady interest

#1,847 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 Torsemide

What Is Torsemide Used For?

Brand names: Demadex, Soaanz

Torsemide tablets are used to treat edema — swelling caused by excess fluid — in people with heart failure, renal disease (kidney disease), or hepatic disease (liver disease). It helps the body get rid of that extra fluid through increased urination.

Torsemide tablets are also used to treat high blood pressure (hypertension). Lowering blood pressure reduces the risk of serious events like strokes and heart attacks. It can be used alone or combined with other blood pressure medications.

See full Torsemide 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
148Moderate
84Minor
2,597No known interaction
148 Moderate 84 Minor 2,597 No interaction
Moderate

148 interactions

Showing 60 of 148 moderate interactions — see all 148 on the Evening Primrose page.

Minor

84 interactions

Showing 60 of 84 minor interactions — see all 84 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 Torsemide, 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 Torsemide supplement interactions › Every supplement checked against Torsemide, ranked by severity Torsemide 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 Torsemide Together: Common Questions

Can you take Evening Primrose with Torsemide?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Evening Primrose and Torsemide interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Torsemide 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.