Avoid in individuals with allergy or sensitivity to gamma linolenic acid. However, no reports of allergy or hypersensitivity have been reported in the available literature.
Side Effects and Warnings
GLA is generally considered nontoxic and well tolerated for up to 18 months. Possible side effects may include upset and bloated stomach, soft stool, nausea and vomiting, flatulence (gas) and belching.
Supplementation with GLA at high levels and for a long duration has been suggested to produce excess levels of arachidonic acid. Chronic use may result in changes in the blood and increase bleeding time. However, studies of diets rich in GLA did not reveal any significant change in blood parameters. Until more research resolves this controversy, caution is advised in those using anticoagulant or antiplatelet (blood thinning) agents.
Pregnancy and Breastfeeding
GLA is not recommended in pregnant or breastfeeding women due to a lack of available scientific evidence.
Adults (over 18 years old)
There is no proven effective dose for GLA in adults. GLA is likely safe when taken by mouth short-term (up to 18 months) in recommended doses. GLA is possibly safe when used long term (up to 36 months). Doses as high as 6 grams per day have been taken for treatment of hyperlipidemia (high cholesterol), and dose as high as 2.8 grams have been taken for rheumatoid arthritis and as an adjuvant treatment with tamoxifen, although there is some concern that these high levels may have adverse effects. However, studies following patients taking large doses, for example, 1.4g to 2.8 grams per day for up to one year, have found GLA to be non-toxic.
Common doses of GLA range between 500-1,000 milligrams per day. For atopic eczema, up to 920 milligrams has been taken daily. For diabetic neuropathy, up to 480 milligrams has been taken daily. Intravenous preparations (injections) have also been studied, although injections should only be given under the supervision of a qualified healthcare professional, including a pharmacist.
Children (under 18 years old)
There is no proven safe or effective dose for GLA in children. However, for atopic eczema, 360-460 milligrams daily has been used.
Interactions with Drugs
GLA may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
Theoretically, GLA may increase the effectiveness of ceftazidime, an antibiotic in a class known as cephalosporins, against a variety of bacterial infections. It is unknown whether effectiveness of other cephalosporin antibiotics are likewise affected.
GLA may alter the effects of certain anti-cancer treatments. Caution is advised.
Theoretically, taking omega-6 fatty acids, such as GLA, during therapy with cyclosporine, a medication used to suppress the immune system after an organ transplant, for example, may increase the immunosuppressive effects of cyclosporine and may protect against kidney damage associated with cyclosporine.
Individuals taking phenothiazines (such as chlorpromazine, fluphenazine, perphenazine, promazine, and thioridazine) to treat schizophrenia should not take evening primrose oil, a source of GLA, because it may interact with these medications and increase the risk of seizures. Theoretically, the same may be true for other GLA containing supplements.
Interactions with Herbs and Dietary Supplements
GLA may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Although not well studied in humans, coenzyme Q10 and vitamin E reversed the inhibition of cell growth associated with GLA. Thus, nutritional antioxidants may inhibit certain effects associated with GLA.