Evening Primrose Oil Ingredients & Drug Interactions
by 21st Century
What is this page for?
First and foremost: checking Evening Primrose Oil against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.
Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy
Evening Primrose Oil is a dietary supplement by 21st Century with 1 active ingredient. Its ingredients are commonly taken for eczema and skin health, pms symptoms, breast pain (mastalgia).Based on those ingredients, 233 medications have a known interaction with it, the most serious rated moderate. The ingredients most likely to interact are Evening Primrose Seed Oil Concentrate. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.
Check Your Meds Against Evening Primrose Oil by 21st Century
Ask about any prescription or over-the-counter medication and we check it for interactions with Evening Primrose Oil by 21st Century — and tell you which ingredient is responsible.
AI summaries are generated from our interaction database for education only — always confirm with your pharmacist. How we use AI
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HelloPharmacist Scorecard of Evening Primrose Oil by 21st Century
Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.
What’s inside
Full disclosure
This product contains one active ingredient: Evening Primrose Seed Oil Concentrate. Evening primrose oil is derived from the seeds of the evening primrose plant and is rich in gamma-linolenic acid (GLA), a fatty acid your body can use.
The softgel capsule is made with gelatin, glycerin, and purified water as inactive ingredients.
Does it work?
Couldn't assess
The evidence for evening primrose oil is mixed and often limited. For asthma, it's rated as possibly ineffective.
For breast pain (mastalgia), it's likely ineffective. For several other uses — including ADHD, acne, and certain gynecological procedures — there simply isn't enough reliable evidence yet to know whether it works.
If you're considering this supplement for a specific health concern, talk with your pharmacist about what the current evidence actually supports.
How safe is it?
Well-documented data
Evening primrose oil is generally well tolerated when taken short-term by mouth. The most common side effects are mild stomach issues: abdominal pain, bloating, diarrhea, indigestion, gas, nausea, and vomiting.
Some people have reported dizziness, headache, skin rash, or acne. However, quality evidence and long-term safety data are limited, so if you plan to use this regularly, discuss it with your doctor or pharmacist.
During pregnancy, the safety data raises some concerns, so it's best avoided unless your doctor directs otherwise. While nursing, there isn't enough reliable information to know whether it's safe, so talk with your healthcare provider.
There's also a theoretical concern that evening primrose oil might lower seizure threshold in patients taking certain antipsychotic medications, so that's another conversation to have with your doctor if that applies to you.
Meds to double-check
Moderate interaction found
Before taking this product, double-check with your pharmacist if you're on blood thinners or antiplatelet drugs (like warfarin or aspirin) — evening primrose oil may increase bleeding risk. Also check if you take lithium, phenothiazines (antipsychotics), or the HIV medication lopinavir/ritonavir.
Finally, if you take any drugs that use the liver enzyme CYP2C9 to metabolize, let your pharmacist know, as evening primrose oil may raise their levels.
The bottom line
Scorecard at a glanceFully disclosed formula with no assessable stated purpose. Moderate medication interactions have been identified, and safety information is well characterized.
Evening primrose oil may be worth considering if you're exploring options for certain conditions and your doctor approves — but the evidence for most uses is weak or unknown. The real caution is with medications: if you take blood thinners, lithium, antipsychotics, or HIV drugs, you need to check with your pharmacist first.
Talk to your pharmacist before starting, especially if you're on any prescription medication or planning pregnancy or nursing.
Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI
Assessment coverage: 1 of 1 active ingredient matched to our full ingredient reviews (monographs). Based on the product label dated Oct 24, 2024.
This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed
General information
Key facts about Evening Primrose Oil, straight from the product label.
| Brand | 21st Century |
|---|---|
| Barcode (UPC) | 740985218280 |
| Net contents | 60 Softgel(s) |
| Market status | On market |
| Date entered into DSLD | Oct 24, 2024 |
| DSLD ID | 304099 |
| Product type | Botanical |
| Supplement form | Softgel Capsule |
| Dietary claims / uses | Nutrient, All Other, Structure/Function |
| Intended target group(s) | Adult Female (18 - 50 Years), Gluten Free |
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.
Supplement Facts
The label details for Evening Primrose Oil by 21st Century, sourced from the NIH Dietary Supplement Label Database.
Supplement Facts
| Ingredient | Amount | % DV |
|---|---|---|
| Evening Primrose Seed Oil Concentrate | 500 mg | -- |
Other ingredients: Gelatin, Glycerin, Water, Purified
Tap any ingredient to jump to its full detail below.
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
Suggested/Recommended/Usage/Directions
Directions: As a herbal supplement, adults take one (1) softgel with any meal, three (3) times daily or as directed by a healthcare provider. Do not exceed recommended dosage. Individual results may vary.
Precautions
Warning: Consult a healthcare provider prior to use if pregnant, nursing, on medications, have a medical condition or are planning a medical procedure.
Stop use and contact a physician if adverse reactions occur.
Keep out of reach of children.
Do not use if product appears to be tampered with or seal is broken.
May contain soy ingredients.
Storage
Store in a cool, dry place.
Formulation
No added sugar, salt, yeast, preservatives or artificial flavors.
Gluten free
FDA Disclaimer Statement
These statements have not been evaluated by the Food and Drug Administration. this product is not intended to diagnose, treat, cure, or prevent any disease.
Formula
Women's health support
Evening Primrose Oil is a source of gamma-linolenic acid (GLA), an essential fatty acid that has been used to support women's health.
FDA Statement of Identity
Herbal Supplement
Seals/Symbols
Guaranteed Quality Laboratory Tested
Is this label outdated? Report a formula or label change and our pharmacy team will review it.
Evening Primrose Oil by 21st Century label
The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.
Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.
View the full label (PDF)The Ingredients in Evening Primrose Oil by 21st Century
This is the 1 active ingredient this product is made of. Select it to open its full monograph.
Serving size1 Softgel(s) Dosage formSoftgel Capsule Servings per container60 Amounts shown are per serving.
Evening Primrose Seed Oil Concentrate
Interacts with233 drugs
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 bre...
Evening Primrose Seed Oil Concentrate monograph & interactionsOther (inactive) ingredients: Gelatin, Glycerin, Water, Purified. These complete the product’s ingredient list but are not active constituents.
Evening Primrose Oil by 21st Century Drug Interactions
HelloPharmacist Interaction Report
21st Century Evening Primrose Oil has documented interactions with several medication types.
The most serious concern is with blood thinners and antiplatelet drugs (like warfarin or aspirin): evening primrose oil may increase bleeding risk because it can reduce how your blood clots and prolong bleeding time.
Read the full breakdown — every affected drug type, severity by severity
It also interacts moderately with lithium, a mood-stabilizing medication — the oil may lower lithium levels and reduce how well it works. There's a moderate interaction with phenothiazines (antipsychotic drugs used for schizophrenia), where there's concern the oil might lower your seizure threshold.
Additionally, it may increase levels of the HIV medication lopinavir/ritonavir (Kaletra). Finally, evening primrose oil theoretically increases levels of drugs metabolized through a liver enzyme called CYP2C9 — a minor interaction affecting several common medications.
Altogether, these interactions span 230 individual medications. If you take any prescription medication, especially blood thinners, lithium, antipsychotics, or HIV treatments, run your exact drugs through the interaction checker below before starting this product.
Check your own medications below · Editorial policy · How we use AI
Want to check YOUR meds against Evening Primrose Oil?
Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.
Go to the checkerIngredients driving the most interactions
Individual Drug Interactions
The ingredients in Evening Primrose Oil interact with 233 drugs. Click any drug to see the details.
1 of the 1 ingredient in Evening Primrose Oil interact with drugs. Each result below shows which ingredient is responsible. Evening Primrose Seed Oil Concentrate
AbciximabReoPro
How Abciximab interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Abciximab interactionAbrocitinibCibinqo
How Abrocitinib interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateCytochrome P450 2c9 (cyp2c9) Substrates, Anticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose may increase the levels and clinical effects of CYP2C9 substrates.
Read the full Evening Primrose Seed Oil Concentrate + Abrocitinib interactionAcenocoumarolSintrom
How Acenocoumarol interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Acenocoumarol interactionAcepromazineAtravet
How Acepromazine interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentratePhenothiazines Moderate
Interaction Summary
Theoretically, taking evening primrose oil with phenothiazines might increase the risk of convulsions.
Read the full Evening Primrose Seed Oil Concentrate + Acepromazine interactionAcetaminophen, AspirinGemnisyn
How Acetaminophen, Aspirin interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Acetaminophen, Aspirin interactionAcetaminophen, Aspirin, CaffeineExcedrin, Excedrin Extra Strength, Excedrin Migraine
How Acetaminophen, Aspirin, Caffeine interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Acetaminophen, Aspirin, Caffeine interactionAcetaminophen, IbuprofenCombogesic
How Acetaminophen, Ibuprofen interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateCytochrome P450 2c9 (cyp2c9) Substrates, Anticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose may increase the levels and clinical effects of CYP2C9 substrates.
Read the full Evening Primrose Seed Oil Concentrate + Acetaminophen, Ibuprofen interactionAcetylsalicylic AcidEntrophen
How Acetylsalicylic Acid interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Acetylsalicylic Acid interactionAlteplase, TpaActilyse, Activase
How Alteplase, Tpa interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Alteplase, Tpa interactionAluminum Hydroxide, Aspirin, Codeine Phosphate, Magnesium HydroxideAscriptin Codeine #2
How Aluminum Hydroxide, Aspirin, Codeine Phosphate, Magnesium Hydroxide interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aluminum Hydroxide, Aspirin, Codeine Phosphate, Magnesium Hydroxide interactionAluminum Hydroxide, Aspirin, Magnesium HydroxideAscriptin
How Aluminum Hydroxide, Aspirin, Magnesium Hydroxide interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aluminum Hydroxide, Aspirin, Magnesium Hydroxide interactionAmitriptyline, PerphenazineEtrafon, Etrafon-A, Etrafon-Forte, Triavil
How Amitriptyline, Perphenazine interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateCytochrome P450 2c9 (cyp2c9) Substrates, Phenothiazines Moderate
Interaction Summary
Theoretically, evening primrose may increase the levels and clinical effects of CYP2C9 substrates.
Read the full Evening Primrose Seed Oil Concentrate + Amitriptyline, Perphenazine interactionAnacaulase-bcdbNexoBrid
How Anacaulase-bcdb interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Anacaulase-bcdb interactionAnagrelideAgrylin
How Anagrelide interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Anagrelide interactionAnisindioneMiradon
How Anisindione interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Anisindione interactionAntithrombin IiiThrombate III
How Antithrombin Iii interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Antithrombin Iii interactionApixabanEliquis
How Apixaban interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Apixaban interactionArgatrobanArgatroban
How Argatroban interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Argatroban interactionAspirinAngettes 75, ASA, Asaphen, Aspirin, Caprin, Cartia +8 more
How Aspirin interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin interactionAspirin, Aluminum Hydroxide, Codeine Phosphate, Magnesium HydroxideAscriptin Codeine #3
How Aspirin, Aluminum Hydroxide, Codeine Phosphate, Magnesium Hydroxide interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Aluminum Hydroxide, Codeine Phosphate, Magnesium Hydroxide interactionAspirin, ButalbitalAxotal
How Aspirin, Butalbital interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Butalbital interactionAspirin, Butalbital, CaffeineFiorinal
How Aspirin, Butalbital, Caffeine interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Butalbital, Caffeine interactionAspirin, Butalbital, Caffeine, Codeine PhosphateFiorinal w/ Codeine
How Aspirin, Butalbital, Caffeine, Codeine Phosphate interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Butalbital, Caffeine, Codeine Phosphate interactionAspirin, Butalbital, Caffeine, PhenacetinMarnal
How Aspirin, Butalbital, Caffeine, Phenacetin interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Butalbital, Caffeine, Phenacetin interactionAspirin, CaffeineAnacin
How Aspirin, Caffeine interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine interactionAspirin, Caffeine, Codeine PhosphateAnacin w/ Codeine
How Aspirin, Caffeine, Codeine Phosphate interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine, Codeine Phosphate interactionAspirin, Caffeine, Dihydrocodeine BitartrateSynalgos DC
How Aspirin, Caffeine, Dihydrocodeine Bitartrate interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine, Dihydrocodeine Bitartrate interactionAspirin, Caffeine, Dover's PwdAcedoval, Dovacet
How Aspirin, Caffeine, Dover's Pwd interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine, Dover's Pwd interactionAspirin, Caffeine, HydrocodoneDamason-P
How Aspirin, Caffeine, Hydrocodone interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine, Hydrocodone interactionAspirin, Caffeine, Isobutylallylbarbituric Acid, PhenacetinLanorinal
How Aspirin, Caffeine, Isobutylallylbarbituric Acid, Phenacetin interacts with Evening Primrose Oil — through 1 ingredient. Tap an ingredient for the detail:
Evening Primrose Seed Oil ConcentrateAnticoagulant/antiplatelet Drugs Moderate
Interaction Summary
Theoretically, evening primrose oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Read the full Evening Primrose Seed Oil Concentrate + Aspirin, Caffeine, Isobutylallylbarbituric Acid, Phenacetin interactionEach ingredient & the kinds of drugs it affects
For each ingredient in Evening Primrose Oil with known interactions, here are the types of medications it can affect. Open any type for the detail — or search your exact drug in the checker above.
Evening Primrose Seed Oil Concentrate
Anticoagulant/Antiplatelet Drugs
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.
Lithium
Theoretically, concomitant use of lithium with evening primrose oil might decrease lithium levels and effects.
In a case report, a patient on a stable dose of lithium for 10 years experienced a reduction in lithium levels after taking evening primrose oil 500 mg daily. Baseline levels were 0.69 mmol/L, which decreased to 0.37 mmol/L after 2 months and 0.23 mmol/L after 3 months of use. Lithium levels increased within 6 weeks of discontinuing evening primrose oil, to 0.73 mmol/L; no clinical effects were noted.
Lopinavir/Ritonavir (Kaletra)
Theoretically, evening primrose oil might increase the levels and effects of lopinavir.
In a case report, an HIV patient who took evening primrose oil (Efamol) along with lopinavir/ritonavir experienced an increase in serum levels of lopinavir to 15.2 mg/L. Six weeks after discontinuing evening primrose oil, levels of lopinavir returned to the normal range of 5-10 mg/L. When re-challenged with evening primrose oil for a week, the patient's lopinavir levels increased from 6.69 to 8.11 mg/L. It is suspected that evening primrose oil increases levels of lopinavir by inhibiting cytochrome P450 3A4 (CYP3A4), which metabolizes lopinavir. However, this effect has not been reported in other research.
Phenothiazines
Theoretically, taking evening primrose oil with phenothiazines might increase the risk of convulsions.
Evening primrose oil contains gamma-linolenic acid (GLA). There is some concern that taking supplements containing GLA might cause seizures, or lower the seizure threshold, when taken with phenothiazines. In one report, three patients with schizophrenia who had received phenothiazines developed EEG changes suggestive of temporal lobe epilepsy after starting treatment with GLA, although none experienced an actual seizure. In another report, two patients with schizophrenia who were stabilized on phenothiazines developed seizures when evening primrose oil 4 grams daily was added. One of these patients had a prior history of seizures. It is unclear whether evening primrose oil had any additive epileptogenic effects with the phenothiazines; there is no evidence that taking evening primrose oil alone causes seizures.
Cytochrome P450 2C9 (Cyp2C9) Substrates
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.
Brand information
Manufacturer and brand details for Evening Primrose Oil, from the product label.
21st Century
See all 21st Century products- Name
- 21st Century HealthCare, Inc.
- Street Address
- 2119 S. Wilson St.
- City
- Tempe
- State
- AZ
- ZipCode
- 85282
- Web Address
- www.21stcenturyvitamins.com
Evening Primrose Oil by 21st Century: Common Questions
Does Evening Primrose Oil by 21st Century interact with any medications?
How can one product interact with so many drugs?
Where does this information come from?
What's actually in this product?
Does evening primrose oil really work for the conditions I'm interested in?
What side effects might I experience?
Is it safe to use while pregnant or breastfeeding?
Can I take evening primrose oil if I'm on a blood thinner?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Not sure if Evening Primrose Oil is safe with your meds?
Our pharmacists answer your medication & supplement questions — free.
Label information is sourced from the NIH Dietary Supplement Label Database and reflects the product version on file; always read your actual product label. This page is for education only and is not a substitute for professional medical advice. Confirm with your pharmacist or doctor before combining supplements and medications.
The Full Monographs Behind Evening Primrose Oil’s Ingredients
Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.
Sources & How We Checked
Evening Primrose Oil's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.
- NIH Dietary Supplement Label Database (DSLD) — The official product label on file for this supplement.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference behind the ingredient interaction data.
Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.
The 33 references behind this product’s interaction data
Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.
Evening Primrose 33 references
- Shaw D, Leon C, Kolev S, Murray V. Traditional remedies and food supplements: a 5-year toxicological study (1991-1995). Drug Saf 1997;17:342-56.
- Laivuori H, Hovatta O, Viinikka L, et al. Dietary supplementation with primrose oil or fish oil does not change urinary excretion of prostacyclin and thromboxane metabolites in pre-eclamptic women. Prostaglandins Leukot Essent Fatty Acids 1993;49:691-4. PubMed
- Dove D, Johnson P. Oral evening primrose oil: its effect on length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women (abstract). J Nurse Midwifery 1999;44:320-4. PubMed
- 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
- Cant A, Shay J, Horrobin DF. The effect of maternal supplementation with linoleic and gamma- linolenic acids on the fat composition and content of human milk: a placebo-controlled trial. J Nutr Sci Vitaminol (Tokyo) 1991;37:573-9. PubMed
- Keen H, Payan J, Allawi J, et al. Treatment of diabetic neuropathy with gamma-linolenic acid. The gamma-Linolenic Acid Multicenter Trial Group. Diabetes Care 1993;16:8-15.
- Blommers J, de Lange-De Klerk ES, Kuik DJ, et al. Evening primrose oil and fish oil for severe chronic mastalgia: a randomized, double-blind, controlled trial. Am J Obstet Gynecol 2002;187:1389-94.. DOI
- Cheung KL. Management of cyclical mastalgia in oriental women: pioneer experience of using gamolenic acid (Efamast) in Asia. Aust N Z J Surg 1999;69:492-4..
- Das UN. The lipids that matter from infant nutrition to insulin resistance. Prostaglandins Leukot Essent Fatty Acids 2002;67:1-12. PubMed
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