Drug & supplement interaction

Evening Primrose + Zafirlukast

Zafirlukast brand name: Accolate.

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

Evening Primrose has a minor interaction with Zafirlukast. 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 Zafirlukast

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

Minor

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

Why this applies to Zafirlukast

Zafirlukast 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 short version: your body uses an enzyme called CYP2C9 to help break down zafirlukast (Accolate). Evening primrose oil contains a fatty acid that, at least in lab studies, can mildly slow that same enzyme down. If it's slowed, a little more zafirlukast could linger in your system, which in theory might nudge up its effects or side effects, like headache, stomach upset, or nausea.

I want to be honest about the strength of this, though. It's theoretical, drawn only from test-tube research, and rated as a minor interaction. For most people taking both, nothing dramatic happens. Zafirlukast isn't a prodrug, so it doesn't flip the other direction. Still, if you notice new side effects or plan to take primrose regularly, run it by your pharmacist or doctor first.

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 Zafirlukast 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. Zafirlukast)
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 Zafirlukast

This page covers Evening Primrose only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Zafirlukast page lists 88 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Adrafinil (moderate), African Wild Potato (moderate), Bacopa (moderate) and Berberine (moderate).

By severity: 1 major · 64 moderate · 23 minor.

Open the Zafirlukast 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 Zafirlukast 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 Zafirlukast 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

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

29 days ago today
Medication Zafirlukast
Top half

#1,237 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 Zafirlukast

What Is Zafirlukast Used For?

Brand name: Accolate

Zafirlukast tablets are used for the prophylaxis (prevention) and chronic treatment of asthma in adults and children 5 years of age and older. It is taken daily to help control ongoing asthma symptoms — not to relieve a sudden asthma attack.

It is available under the brand names Accolate and Zafirlukast as an oral tablet.

See full Zafirlukast 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 Zafirlukast, 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 Zafirlukast supplement interactions › Every supplement checked against Zafirlukast, ranked by severity Zafirlukast 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 Zafirlukast Together: Common Questions

Can you take Evening Primrose with Zafirlukast?
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 Zafirlukast 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 Zafirlukast 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.