Common Name Evening Primrose
Latin Binomial Oenothera biennis L.
Family: Onagraceae
Part Used Seed Oil
Pharmacopoeial & Other Monographs
Active Constituents
  • Linoleic acid, 18:2 (n-6)
  • gamma-linolenic acid (GLA), 18:3 (n-6)
  • Oleic acid, 18:1 (n-9)
  • Palmitic acid, 16:0
  • Stearic acid, 18:0
Food Use The root can be eaten as a vegetable with a peppery flavor. (48)
The seed oil contains the essential fatty acids (EFAs) linoleic acid and gamma-linolenic acid.
Contra-Indications Evening primrose should be used with caution by patients with a history of epilepsy or who are taking phenothiazines. Pregnancy and lactation
No data is available and therefore evening primrose oil should not be taken during pregnancy. Both linolenic acid and gammalinolenic acid are normally present in breast milk.
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Herbal Use/Indication An infusion of the whole plant is thought to have a sedative and astringent properties, and has traditionally been used for asthmatic coughs, gastrointestinal disorders, whooping cough, and as a sedative painkiller. Poultices were reputed to ease bruises and to speed wound-healing. (48)
Evening Primrose oil has been used for premenstrual syndrome, psoriasis, multiple sclerosis, hypercholesterolaemia, rheumatoid arthritis, Reynaurd's phenomenon, Sjorgren's syndrom, post-viral fatigue syndrome, asthma, and diabetic neuropathy. (48)(49)(50)(51)
Pharmacological Action The seed oil of evening primrose contains the EFAs linoleic acid and gamma-linolenic acid (GLA). Both are prostaglandin precursors. GLA is though to increase the ratio of non-inflammatory compounds. (1)
GLA and its metabolite dihomogamma-linolenic acid (DGLA) are precursors of both of the inflammatory prostaglandins E2 (PGE2) series via arachadonic acid (AA), and the less inflammatory prostaglandin E1 (PGE1) series. (1)
PGE1 acts as an anti-inflammatory, immunoregulatory, vasodilator, inhibits platelet aggregation and cholesterol bio-synthesis, promotes hypo-tension, and elevates cyclic AMP (inhibits phospholipase A2). (49)(50)(51)
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GLA is thought to increase the DGLA:AA ratio. DGLA inhibits the conversion of arachidonic acid to inflammatory lipoxygenase metabolites such as leukotrienes. (1)
PGE1 inhibits the enzyme phospholipase A2, which is responsible for removing AA from the phospholipid membrane stores. DGLA desaturation to AA is a rate-limiting step in humans and proceeds slowly. (51)
The body metabolizes linolenic acid (LA) to gamma-linolenic acid (GLA). This conversion is reduced in aging, diabetes, cardiovascular disorders, and high cholesterol intake, high alcohol intake, viral infections, cancer, nutritional deficits, atopic eczema, and PMS. (49)(50)(51)
Direct dietary supplementation of GLA bypasses this slow-step, converting LA to GLA, and increases the ratio of DGLA:AA.
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Summary There is a large body of literature on the effects of evening primrose oil and gamma-linolenic acid (GLA) in various disease states associated with low concentrations of GLA. The available data are inconclusive and/or arise from studies with methodological limitations. The efficacy of evening primrose oil in these conditions, therefore, has not been established and further, rigorous research is required. (1)
Dosage Dose is based on gamma-linolenic acid (GLA) content equal to 8%.
Product licenses in the UK, that followed these dosing regimens, were withdrawn in 2002 due to lack of data to support the efficacy of the product. Should not be taken for more than three months.
Atopic eczema: 6-8g per day for adults; 2-4g per day for children.
Cyclical & Non-cyclical mastalgia: 3-4g per day.
Side effects Evening primrose oil appears to be well tolerated when taken at recommended doses. (51)
Mild gastrointestinal effects, indigestion, nausea, soft stools, and headache have been reported. (51)(48)
Evening primrose may increase the risk of temporal lobe epilepsy in schizophrenic patients being treated with epileptogenic drugs, such as phenothiazines. (52)

BP 2007

British Pharmacopoeia 2007. London: The Stationery Office, 2007.

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Martindale 35th Edition

Martindale. The Complete Drug Reference, 35th edn. (Sweetman S, ed.) London: Pharmaceutical Press, 2007.

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Ph Eu 2007

European Phamcopoeia, 5th edn, and Supplements 5.1-5.7. Strasbourg: Council of Europe, 2004-2007.

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Briggs CJ. Evening primrose. Rev Pharm Can 1986; 119: 249-254.

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Li Wan Po A. Evening primrose oil. Pharm J 1991; 246: 670-676.

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Barber HJ. Evening primrose oil: a panacea? Pharm J 1988; 240: 723-725.

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Horrobin DF. Gammalinolenic acid: an intermediate in essential fatty acid metabolism with potential as an ethical pharmaceutical and as a food. Rev Contemp Pharmacother 1990; 1: 1-45.

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Barnes J, Anderson LA, Phillipson DJ. Herbal Medicines. Third edition. Grayslake, Il Phrmaceutical Press; 2007. 710p.

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Aron. Data Sheet Compendium 1994-95, 1520-1. Efamast, Epogam, Epogam Pedietric (Searle).

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