Evening Primrose Oil
Scientific Names: Oenothera biennis and other Oenothera species
Other Common Names: Sun drop, gamma-linolenic acid (GLA), omega-6-fatty acid
Overall Safety: 😊
Therapeutic Efficacy and Considerations:
Atopic Dermatitis: 😊 Several trials have examined use in atopic dermatitis in children and adults with positive results in reduction of itching, redness, and other symptoms and two meta-analyses concluded that EPO does provide benefit. The evidence does support a recommendation for use, but appropriate diagnosis is important as EPO has no benefit for non-atopic dermatitis. EPO may also not be as effective with high potency steroid use. Dose: 4-6 gm EPO daily for adults, 3 gm daily for children.
Diabetic Neuropathy: 😊 Two trials, one large and of high quality, have found benefit for reduction of neuropathy symptoms, with some patients experiencing reversal of symptoms. Although more research is needed to confirm and characterize the extent of efficacy, the evidence does support consideration of EPO as an adjunctive treatment for diabetic neuropathy. Dose: 4 gm EPO daily.
Hypercholesterolemia: 😐 Two small preliminary studies suggest that EPO may reduce triglycerides and increase apolipoprotein B levels. More research is warranted, but current evidence is not sufficient to recommend use for this indication. Dose: 3-3.3 gm EPO daily.
Rheumatoid Arthritis: 🙁 Three small trials with many methodological limitations have demonstrated conflicting results. Current evidence does not support a recommendation for use for this indication.
Premenstrual Syndrome: 🙁 Three small trials with many methodological limitations have demonstrated conflicting results. More research is warranted, but current evidence does not support a recommendation for use for this indication.
Sjogren’s Syndrome: 🙁 Two trials, one large and of high quality, have demonstrated no improvement in symptoms in Sjogren’s Syndrome. Use for this indication is not recommended.
Mastalgia: 🙁 One controlled trial compared placebo of wheat germ oil or corn oil to EPO with placebo of corn oil or EPO with fish oil; no benefit was noted. Use for this indication is not recommended.
Menopausal Flushing: 😐 One small high-quality trial noted significant decreases in hot flushes. Although more research is needed, EPO may be considered an option for women who refuse or cannot tolerate hormone replacement therapy. Dose: 1000 mg EPO with 10 mg vitamin E BID.
Note: No benefits were shown in studies for systemic sclerosis, chronic schizophrenia, attention-deficit hyperactivity disorder, obesity, liver cancer, asthma, tardive dyskinesia, osteoporosis, multiple sclerosis, or claudication.
Evening Primrose Oil (EPO) contains 2-16% gamma-linolenic acid (GLA), 65-80% linoleic acid, and vitamin E. Linolenic and linoleic acid (LA) are essential fatty acids; LA is converted into GLA, but via a long process. GLA is a prostaglandin precursor and is thought to be responsible for the anti-inflammatory activities. It is rapidly converted into dihomo-gamma-linolenic acid and arachidonic acid. GLA is believed to be that active constituent, but the drawback to this theory is the relatively low percentage of GLA: large doses, often more than 8 capsules daily, would be needed to achieve a therapeutic dose of GLA. EPO does appear to be more effective than other sources of GLA, such as borage seed oil, black currant seed oil, and fungal oils (black current seed oil and borage seed oil). Researchers theorize that these other sources may contain a thromboxane synthesis promoter which counteracts the effects of GLA. GLA may also have angiotensin II receptor inhibition properties and have the potential to lower blood pressure.
Phenothiazines (due to documented increased risk of seizures, especially in conjunction with vitamin E use) and anticoagulant/antiplatelet drugs (slight additive inhibition of platelet aggregation). Animal evidence suggests blood pressure lowering activity, so additive effects with antihypertensive agents may occur.
Bleeding disorders, pregnancy, patients undergoing anesthesia, epilepsy/seizures, and schizophrenia. The latter two cautions are because of a potential interaction with phenothiazines rather than the disease state itself.
Generally, well tolerated. Some reports of headache, seizure (possibly due to drug interactions), GI discomfort, and possible complications with pregnancy.