Health Care Professional Information
EPO, night willow herb, fever plant, king’s cure-all
Derived from the plant Oenothera biennis, evening primrose oil (EPO) is used for rheumatoid arthritis, premenstrual syndrome, eczema, fatigue, diabetic neuropathy and mastalgia. It contains gamma-linolenic acid (GLA), a primary fixed oil, which is converted to dihomo-gamma-linolenic-acid, a prostaglandin precursor (2) (3).
In vitro studies indicate that EPO may inhibit platelet aggregation (6) (7) but clinical data are inconsistent.
Small studies suggest its effectiveness against atopic dermatitis (18) and 5-azacitidine-induced skin reactions in patients with myelodysplastic syndromes (MLD) (19), and in preventing weight regain following extensive weight loss (5).
Conclusions from a meta analysis indicate utility of EPO in relieving symptoms of rheumatoid arthritis (21). Supplementation with vitamin E and EPO reduced cyclical mastalgia (20); however, a meta analysis showed that EPO is ineffective against mastalgia (1)and a systematic review suggests it may not be useful in alleviating premenstrual syndrome (22).
Evening primrose oil has not been studied extensively for cancer, but data from one study indicate that GLA may be an effective adjunctive therapy for breast cancer (4). More studies are needed.
Reduced seizure threshold has been reported with a combination of EPO and phenothiazine antipsychotics (9).
Although EPO does not have intrinsic estrogenic properties, some commercial products combine EPO with phytoestrogens. Therefore patients with hormone-sensitive cancer should use EPO products with caution.
- Cancer treatment
- Diabetic neuropathy
- GI disorders
- High cholesterol
- Menopausal symptoms
- Premenstrual syndrome
- Rheumatoid arthritis
- Fixed oils: Cis-Linoleic acid, cis-gammalinolenic acid (GLA), oleic acid, palmitic acid and stearic acid
Mechanism of Action
Theoretically, GLA can be converted directly to the prostaglandin, precursor dihomo-GLA. The administration of the oil might be beneficial to individuals unable to metabolize cis-linolenic acid to GLA and to produce subsequent intermediates of considerable metabolic significance, including prostaglandins.
Repeated oral administration of evening primrose oil (480 mg/day gamma-linoleic acid/day) to healthy volunteers resulted in mean Cmax of approximately 20.7-22.6 mcg/ml. Gamma-linoleic acid levels were approximately 4.5 times greater from baseline in all patients, but serum levels of other fatty acids did not change significantly from baseline. Gastric absorption and Tmax for morning doses was longer than Tmax for identical doses given in the evening.
Pregnant women should not take evening primrose oil due to increased risk of pregnancy complications. (8)
Reported: Headache, GI upset, nausea, and increased risk of pregnancy complications
Petechiae and ecchymoses were observed in a neonate whose mother used raspberry leaf tea and evening primrose oil (vaginally and orally) 1 week before childbirth.
Anticoagulants / Antiplatelets: May have additive effects and increase risk of bleeding.
Phenothiazines (e.g. fluphenazine): Evening primrose oil may lower the seizure threshold and precipitate seizures in patients taking phenothiazines.
Literature Summary and Critique
Srivastava A, et al. Evidence-based management of Mastalgia: a meta-analysis of randomised trials. Breast. Oct 2007;16(5):503-512.
In a meta-analysis of commonly used treatments for mastalgia, including Evening primrose oil (EPO), Bromocriptine, Danazol, and Tamoxifen, previously reported randomized, placebo-controlled trials were analyzed. Three randomized, controlled trials of EPO were included along with 1 trial of gamma-linolenic acid. Although Bromocriptine, Danazol, and Tamoxifen improved mastalgia, EPO was ineffective and therefore should not be used for mastalgia relief.
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- Srivastava A, Mansel RE, Arvind N, et al. Evidence-based management of Mastalgia: a meta-analysis of randomised trials. Breast. Oct 2007;16(5):503-512.
- Belch JJ, Hill A. Evening primrose oil and borage oil in rheumatologic conditions. Am J Clin Nutr 2000;71:352S-6S.
- Tyler, V. Herbs of Choice, the Therapeutical Use of Phytomedicinals. Binghamton: Pharmaceutical Press; 1994.
- Kenny FS, et al. Gamma linolenic acid with Tamoxifen as primary therapy in breast cancer. Int J Cancer 2000; 85:643-8.
- Schirmer MA, Phinney SD. Gamma-linolenate reduces weight regain in formerly obese humans. J Nutr. Jun 2007;137(6):1430-1435.
- De La Cruz JP, Martin-Romero M, Carmona JA, et al. Effect of evening primrose oil on platelet aggregation in rabbits fed an atherogenic diet. Thromb Res. Jul 1 1997;87(1):141-149.
- 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 Acids. Nov 1994;51(5):311-316.
- Dove D, Johnson P. Oral evening primrose oil: its effect on length of pregnancy and selected intrapartum outcomes in low-risk nulliparous women. J Nurse Midwifery. 1999 May-Jun;44(3):320-4.
- Holman CP, et al. A trial of evening primrose oil in the treatment of chronic schizophrenia. J Orthomolecular Psychiatry 1983;12:302-4.
- Newall C. Herbal Medicines, A Guide for Health Care Professionals. London: Pharmaceutical Press; 1997.
- Martens-Lobenhoffer J, Meyer FP. Pharmacokinetic data of gamma-linoleic acid in healthy volunteers after the administration of evening primrose oil (Epogam). Int J Clin Pharmacology Therapeutics 1998;36:363-6.
- Wedig KE, Whitsett JA. Down the primrose path: petechiae in a neonate exposed to herbal remedy for parturition. J Pediatr. Jan 2008;152(1):140, 140 e141.
- Zurier RB, et al. Gamma-linolenic acid treatment of rheumatoid arthritis. A randomized, placebo-controlled trial. Arthritis Rheum 1996;39:1808-17.
- Budeiri D, et al. Is evening primrose oil of value in the treatment of premenstrual syndrome? Control Clin Trials 1996;17:60-8.
- Keen H, et al. Treatment of diabetic neuropathy with gamma-linolenic acid. Diabetes Care 1993;16:8-15.
- Pye JK, et al. Clinical experience of drug treatment for mastalgia. Lancet 1985;2:373-7.
- Blommers J, et al. Evening primrose oil and fish oil for severe chronic astalgia: a randomized, double-blind, controlled trial. Am J Obstet Gynecol. 2002 Nov;187(5):1389-94.
- Senapati S, Banerjee S, Gangopadhyay DN. Evening primrose oil is effective in atopic dermatitis: a randomized placebo-controlled trial. Indian J Dermatol Venereol Leprol. 2008 Sep-Oct;74(5):447-52.
- Platzbecker U, Aul C, Ehninger G, Giagounidis A. Reduction of 5-azacitidine induced skin reactions in MDS patients with evening primrose oil. Ann Hematol. 2009 Aug 28. [Epub ahead of print]
- Pruthi S, Wahner-Roedler DL, Torkelson CJ, et al. Vitamin E and evening primrose oil for management of cyclical mastalgia: a randomized pilot study. Altern Med Rev. 2010 Apr;15(1):59-67.
- Dante G, Facchinetti F. Herbal treatments for alleviating premenstrual symptoms: a systematic review. Journal of psychosomatic obstetrics and gynaecology. 2011 Mar;32(1):42-51.
How It Works
Bottom Line: Evening primrose oil has not been shown to treat or prevent cancer.
Scientists have not figured out how exactly evening primrose oil exerts its effects, but theorize that it has anti-inflammatory activity. It may be beneficial for patients with mastalgia (breast pain). It may also help those with diabetes, heart disease, cancer, premenstrual syndrome, eczema, or high cholesterol but there is not enough data to support such effects.
- To treat cancer
Evening primrose oil had no effect on tumor size or survival in patients with liver cancer. In another study, patients with breast cancer who received GLA in addition to Tamoxifen had faster response to treatment than those who received Tamoxifen alone.
- To treat diabetic neuropathy
Studies in animals suggest that evening primrose oil can prevent or reverse diabetic neuropathy, and one clinical trial almost 20 years ago supported this use. However, more research is needed.
- To treat eczema
Clinical trials show conflicting results.
- To treat gastrointestinal disorders such as colitis or irritable bowel syndrome
One clinical trial has studied the effects of evening primrose oil on ulcerative colitis, showing weak effects. In general, there is little support for this use.
- To reduce high cholesterol
One small clinical trial suggested that evening primrose oil led to a decrease in LDL (“bad”) cholesterol, but these findings have not been confirmed by additional studies.
- To relieve breast pain (mastalgia)
A handful of clinical trials support this use, especially for mastalgia associated with menstrual cycle.
- To relieve menopausal symptoms
One clinical trial found that evening primrose oil was no better than placebo at relieving menopausal hot flashes.
- To prevent premenstrual syndrome (PMS)
Results of clinical trials are inconsistent.
- To reduce inflammation of rheumatoid arthritis
Clinical studies show that evening primrose rose oil may be useful in reducing symptoms of RA.
Mastalgia (breast pain):
The results of several clinical trials and volunteer studies conducted in the United Kingdom were compiled to measure the effect of evening primrose oil on mastalgia (breast pain). Overall, evening primrose oil was found to have a similar level of effectiveness as bromocriptine (a drug used to treat mastalgia), having beneficial effects in 44% of women treated. However, this was less effective than treatment with danazol, another medication. Treatment with evening primrose oil was more effective in women with cyclical mastalgia than in women with non-cyclical pain. Another study found evening primrose oil no more effective than wheat-germ oil in the treatment of breast pain.
Do Not Take If
- You are pregnant.
- You are taking anticoagulants or antiplatelet agents (Evening primrose oil may enhance their effects.)
- You are taking phenothiazines such as fluphenazine (Evening primrose oil may lower the seizure threshold and increase the risk of seizures in patients taking phenothiazines).
Last updated: June 4, 2012