Evening Primrose Oil
- Indications with possible efficacy:
- Indications with possible, but poorly documented efficacy:
- Indications with no proof of efficacy:
Chronic fatigue syndrome
Flushing associated with menopause
Hyperactivity in children
Post-viral fatigue syndrome
Weight loss (to enhance)
- Risk of Drug Interactions: Low
- Adverse Effects: Not Frequent
Part of the plant used: seeds (oil)
Evening primrose oil contains essential fatty acids: gamma linoleic acid (GLA) and linoleic acid. GLA appears to inhibit production of inflammatory metabolites. Low levels of GLA are associated with some diseases.
The body can naturally produce small quantities of gamma linoleic acid. Taking GLA supplements can significantly increase blood levels.
Evening primrose oil is usually available in oral capsules standardized to 8% GLA.
Direction of use
It is administer 2 or 3 times daily with meals and use should last at least 3 to 6 months.
- Atopic eczema:
Mild improvement of atopic eczema symptoms.
Children less than 12 years of age: 160 to 320 mg of GLA
Adult: 160 to 640 mg daily.
- Diabetic neuropathy:
Used doses: 320 to 480 mg of GLA daily have been used.
Available data are still limited. In one study, 90% of women with endometriosis experienced a reduction of their symptoms when taking GLA combined with eicosapentaenoic acid.
Used doses: 160 to 320 mg of GLA daily
GLA and fish oils with calcium supplements seems to be more effective then calcium to increase bone mineral density.
- Raynaud's disease:
Evening primrose oil could attenuate extremity excessive sensitivity to cold temperature.
- Rheumatoid arthritis:
A few studies have shown improvement of subjective symptoms when compared to placebo. Data are still limited.
Used doses: 240 to 540 mg of GLA daily for at least 6 to 12 months before results are observed.
There is insufficient reliable information to conclude that evening primrose is effective in any other indication.
- Side effects
Evening primrose oil is not associated with severe toxicity. It is usually well tolerated. On occasions, people may suffer from upset stomach, nausea, soft stools or headaches. Large doses may be associated with abdominal pain.
Contraindicated if active bleeding and epilepsia (may decrease seizure threshold).
It is believed that patients taking drugs that affect the nervous system (phenothiazines) may be more at risk for seizures. Evening primrose oil apparently interacts with oral anticoagulants, such as Coumadin, and increase the effects of antiplatelet agents. Bleeding risks may be increased. Before taking evening primrose, check with your pharmacist to make sure that there are no interactions with your regular medication.
- Pregnancy and lactation
Evening primrose oil might increase the risk for delivery complications. Pregnant women should not take this product. High levels of GLA are naturally excreted in breast milk. It is reasonable to assume that evening primrose oil may be taken while breast feeding.
- Evening primrose oil is approved in the United Kingdom as a prescription product for the treatment of atopic eczema and mastalgia. In Europe, doctors use it to treat diabetic neuropathy. In Canada, it is approved as a dietary supplement to increase the intake of essential fatty acids.
- Many evening primrose oil formulations contains vitamin E.
In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication.
Medicinal plant contents vary naturally from plant to plant - just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.
For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.
- Pharmacist's Letter, CE Booklet: Therapeutic Uses of Herbs Part. 2, Spring 1998
- Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2010
- Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
- Barnes J. et Al. Herbal Medicines, 2nd edition, Pharmaceutical Press, 2002
- Passeportsanté.net. Huile d'onagre. www.passeportsante.net
- Rotblatt M. et Ziment I. Evidence-Based Herbal Medicine, Hanley & Belfus, 2002
- Natural Therapeutics Pocket Guide, 2000-2001
- The Review of Natural Products, 6th Edition, 2010
- Health Canada, Natural Products Database
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.