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Interactions

Interactions with Drugs

Because of reported seizures in people taking evening primrose oil alone or in combination with certain medications used to treat mental illness, patients should use caution when combining evening primrose oil with medications like chlorpromazine (Thorazine®), thioridazine (Mellaril®), trifluoperazine (Stelazine®), or fluphenazine (Prolixin®). Individuals undergoing surgery requiring general anesthesia may be more sensitive to developing seizures, and should stop taking evening primrose oil two weeks ahead of time. In people with a history of seizures, doses of anti-seizure medications may require adjustment because evening primrose oil may increase the risk of seizures.

An ingredient of evening primrose oil, gamma-linolenic acid, is reported to lower blood pressure in animal studies. Although human studies do not show clear changes in blood pressure, people taking certain blood pressure medications should consult with a healthcare professional before starting evening primrose oil.

Interactions with Herbs and Dietary Supplements

In animal studies, gamma-linolenic acid (an ingredient of evening primrose oil) is reported to lower blood pressure. Therefore, in theory, evening primrose oil may have effects on blood pressure, and should be used cautiously when combined with other agents that may lower blood pressure.

Attribution

This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com): E-P Barrette, MD (Case Western Reserve University School of Medicine); Ethan Basch, MD, MSc, MPhil (Memorial Sloan-Kettering Cancer Center); Samuel Basch, MD (Mt. Sinai Medical Center); Steve Bent, MD (University of California, San Francisco); Heather Boon, BScPhm, PhD (University of Toronto); Cynthia Dacey, PharmD (Northeastern University); Edzard Ernst, MD, PhD (University of Exeter); Paul Hammerness, MD (Massachusetts General Hospital); Catherine Ulbricht, PharmD (Massachusetts General Hospital); Mamta Vora, PharmD (Northeastern University); Wendy Weissner, BA (Natural Standard Research Collaboration); Peter Wolsko, MD (Harvard Medical School).

Bibliography

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Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.