EPO supplementation should be halted before any surgical procedure. Because of its possible inhibition of lymphocyte function, those with immune deficiency disorders, such as AIDS, should exercise caution in the use of EPO. Evening primrose oil has been studied for several different health problems, but there is no high-quality evidence for any use of it. Research suggests that evening primrose oil is not helpful for premenstrual syndrome or symptoms of menopause. People who are pregnant or have epilepsy should avoid evening primrose oil. It should not be taken with drugs that increase the risk of seizures, drugs that lower blood pressure, phenothiazine drugs or anesthesia.