Materia Medica

Oenothera biennis,  Onagraceae.  Commonly known as evening primrose.

Evening primrose is indigenous to the United States and was used by several Native American groups both as food and medicine.  They ate the leaves, roots and seedpods and made medicines from these parts also. It was used for asthma treatment, as a painkiller, for hemorrhoids and as a poultice for wounds and bruises.  Europeans began using the plant during the eighteenth century as poultice for wounds. It was also a popular Shaker medicine.  They recommend the leaves or roots for healing wounds and a tea of the leaf and root to settle an upset stomach.

Evening primrose is a biannual plant, indigenous to the North America, that is often found in old fields, ditches and waste places.  The first year it grows a rosette of leaves and in the second year it has creamy to bright yellow four petaled flowers.  These flowers bloom after sunset, throughout the night and on overcast days from June through September.  It is from 3 to 8 feet tall.

Oil pressed from the seed is the primary product.  It is available in capsules.

Evening primrose oil (EPO) contains essential fatty acids that can help balance body deficiencies due to diet or system imbalances.  These imbalances can be related to aging, diabetes, arthritis, asthma, inflammations, metabolic irregularities and alcoholism.  EPO consists of cis-linoleic acid, alpha-linolenic acid and cis-gamma-linolenic acid (GLA). GLA  is found in few other dietary sources.  GLA can theoretically be converted directly to the prostaglandin precursor dihomo-GLA (DGLA), bypassing the conversion step of  linoleic acid, which is more common in the body.^[1]   Both GLA and DGLA are involved with the formation of prostaglandins, favoring the production of PGE1 which are vasodilatory, immune-modulating, anti-inflammatory, inhibit platelet aggregation, block cholesterol synthesis and lower blood pressure.^[2]

Many studies have been conducted with EPO with variable results, some favorable and some not.  Atopic dermatitis and other dermatologic disorders are treated with EPO and have been approved in Germany for this use.^[3]  Women with cyclical mastalgia or noncyclical mastalgia have shown positive results from treatment with EPO.^[4]  Although frequently recommended for PMS  and apparently of some value, more studies need to be done, the results thus far have been variable and many of the studies have been flawed. Menopausal hot flashes appear not to be favorable effected by EPO.^[5] Rheumatoid arthritis, lowering plasma cholesterol, cardiovascular disease, multiple sclerosis and cancer are under investigation for improvement by EPO, again with variable results. Diabetic neuropathy has shown improvement in trials, particularly in relatively well controlled than in poorly controlled diabetic patients.

GLA and LA are important components of breast milk, and EPO is recommended for nursing mothers and during pregnancy.^[6]

EPO is a popular supplement for essential fatty acids and is used in the treatment of  PMS, mastalgia, cardiovascular disease, rheumatoid arthritis, multiple sclerosis, diabetic neuropathy, atopic dermatitis and other skin disorders.

Seeds contain up to 25% of a fixed oil which can contain from 50% to 70% cis-linoleic acid and from 7% to 10% cis-GLA.  Cis-6,9,12-ocadecatrienoic acid, oleic, palmitic and stearic acids, steroids, campesterol, beta-sitosterol are also contained in EPO.

Dosage Parameters: The maximum recommended dosage should not exceed 4 g a day, although occasional short time usage for atopic eczema the dosage could be higher, up to 8 g a day. For children, the advisable dose is 2 to 4 grams a day.

EPO is contraindicated when patients are taking epiloptogenic drugs such as phenothiazines.^[7]  EPO may worsen temporal lobe epilepsy or schizophrenia if administered with conventional drug therapy.