Evening Primrose Oil Print Page

Common Names: Evening primrose, primrose oil
Scientific NamesOenotherabiennis

Bottom Line

Effectiveness:  Limited evidence has shown that evening primrose oil is not effective for the management of rheumatoid arthritis. Use in rheumatic conditions is not recommended.

Safety:  Generally well tolerated for short term use up to 1 year.

What is Evening Primrose?

  • Evening primrose belongs to a family of wild flowering plants native to the Americas. The oil from the seeds is used to make medicine.

What it is it used for in people with rheumatic conditions?

  • Evening primrose oil has been used to manage of rheumatoid arthritis.

How is it thought to work?

  • Evening primrose oil contains an omega-6 essential fatty acid called gamma-linolenic acid.  It is involved in regulating inflammation and the immune system.

Does it Work? What the Science Says:

Evening primrose oil: up to 3 grams per day (NIH, Natural Comprehensive)
  • Some preliminary evidence suggests that evening primrose oil may reduce the dose of NSAID required. 
  • However, several systematic reviews found evening primrose oil does not significantly improve pain or functionality score compared to placebo.
  • Most of the trials are small and of poor quality. No significant benefit has been seen in studies. 
  • Use of evening primrose oil is not recommended for rheumatoid arthritis.

What are possible side effects and what can I do about them?

  • Generally well-tolerated orally if taken within recommended doses. It can cause stomach upset, nausea, vomiting, and heartburn, a reduced blood pressure, headache and dizziness.


With drugs:

  • Evening primrose oil may reduce the amount platelets clump together (platelet aggregation).  It may interact with anticoagulant/antiplatelet drugs by increasing risk of bruising and/or bleeding.
    • Common antiplatelet and anticoagulant drugs include: warfarin (Coumadin), ASA (Aspirin), and clopidogrel (Plavix), ticagrelor (Brilinta), prasugrel (Effient), enoxaparin (Lovenox), dalteparin (Fragmin), dabigatran (Pradaxa), rivaroxaban (Xarelto), apixaban (Eliquis) and others.
  • Evening primrose oil may decrease the level of lithium in patients who are taking lithium for bipolar disorder (case report); follow lithium levels closely when starting and stopping evening primrose oil

With other diseases:

  • Evening primrose oil can slow blood clotting (antiplatelet effects). This may increase risk of bleeding during surgeries. Stop evening primrose oil at least 2 weeks prior to surgical procedures.
  • There are reports that evening primrose may increase risk of seizures in patients with conditions such as epilepsy and schizophrenia who are treated with phenothiazines (e.g. chlorpromazine, fluphenazine, prochlorperazine). Until more is known, take evening primrose with caution if you have a seizure disorder or schizophrenia. 
  • Taking evening primrose oil during pregnancy may increase risk of complications. Avoid in pregnancy.

With other natural health products:

  • Evening primrose oil may interact with other natural health products that might affect the amount platelets clump together (called platelet aggregation). This could increase the risk of bleeding. 
    • Such as: garlic, ginger, ginkgo, certain types of ginseng, red clover, and others.

For more information about evening primrose oil, consult your physician and pharmacist.

What is Rheumatology?

Rheumatologists see over 100 different types of diseases. We are known for seeing arthritis, however, we also see many other conditions.

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