Evening primrose
Evening primrose

Background

Evening primrose (Oenothera biennis) is a plant native to the Americas. Its yellow flowers open at sunset. The oil in its seeds contains omega-6 fatty acids.

Evening primrose oil contains gamma-linolenic acid (GLA). GLA is an omega-6 essential fatty acid that has anti-inflammatory effects in the body.

People use evening primrose oil for premenstrual syndrome (PMS), menopause symptoms, arthritis, high cholesterol, acne, and many other conditions, but there is no good scientific evidence to support these uses.

Don't confuse evening primrose oil with other plants or oils that are sources of GLA and omega-6 fatty acids, such as black currant, borage, and flaxseed oil.
When taken by mouth: Evening primrose oil is likely safe for most people when taken in doses up to 6 grams daily for up to 1 year. It might cause mild side effects including upset stomach, nausea, diarrhea, and headache in some people. There isn't enough reliable information to know if other parts of the evening primrose plant are safe or what the side effects might be.

When applied to the skin: There isn't enough reliable information to know if evening primrose is safe or what the side effects might be.

Special Precautions & Warnings:

Pregnancy: Taking evening primrose oil by mouth is possibly safe during pregnancy. Taking up to 4 grams by mouth daily for up to 10 weeks seems to be safe. But until this is confirmed, be cautious. Taking evening primrose oil during the last weeks of pregnancy might delay labor. Don't use this product close to the end of pregnancy.

Breast-feeding: It is possibly safe to take evening primrose oil while breast-feeding, but it's best to check with your healthcare provider first.

Children: Evening primrose oil is possibly safe when taken by mouth in doses up to 6 grams daily. It is also possibly safe when applied to the skin.

Bleeding disorders: Evening primrose oil might increase the chance of bruising and bleeding. Don't use it if you have a bleeding disorder.

Epilepsy or another seizure disorder: Evening primrose oil might make seizures more likely in some people.

Surgery: Evening primrose oil might increase the chance of bleeding during or after surgery. Stop using it at least 2 weeks before a scheduled surgery.

Effectiveness

NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
Likely ineffective Effectiveness definitions
  • Breast pain (mastalgia). Taking evening primrose oil by mouth doesn't seem to reduce breast pain.
There is interest in using evening primrose for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Possibly ineffective Effectiveness definitions
  • Asthma. Taking evening primrose oil by mouth doesn't seem to improve asthma symptoms.
Insufficient evidence Effectiveness definitions

Dosing & administration

Evening primrose oil has most often been used by adults in doses of 2-6 grams by mouth daily for 3-12 months. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Lithium

Interaction Rating=Moderate Be cautious with this combination.

Evening primrose oil might decrease the levels of lithium in the body. Taking evening primrose oil along with lithium might decrease the effects of lithium.

Lopinavir/Ritonavir (Kaletra)

Interaction Rating=Moderate Be cautious with this combination.

Evening primrose oil might decrease how quickly the body breaks down lopinavir / ritonavir. Taking evening primrose oil along with lopinavir / ritonavir might increase the effects and side effects of lopinavir / ritonavir.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Interaction Rating=Minor Be watchful with this combination.

Some medications are changed and broken down by the liver. Evening primrose oil might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)

Interaction Rating=Moderate Be cautious with this combination.

Evening primrose oil might slow blood clotting. Taking evening primrose oil along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Phenothiazines

Interaction Rating=Moderate Be cautious with this combination.

Taking evening primrose oil with phenothiazines might increase the risk of a seizure in some people.

Interactions with herbs & supplements

Herbs and supplements that might slow blood clotting: Evening primrose oil might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include garlic, ginger, ginkgo, nattokinase, and Panax ginseng.

Interactions with foods

There are no known interactions with foods.
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This monograph was last reviewed on 04/07/2024 10:00:00 and last updated on 19/10/2022 06:27:54. Monographs are reviewed and/or updated multiple times per month and at least once per year.
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