Evening primrose oil and treatment of premenstrual syndrome.

The therapeutic effectiveness of evening primrose oil (Efamol, Vita-Glow) in the relief of 10 symptoms associated with premenstrual syndrome (PMS) as well as menstrual symptoms was studied in 38 women. The prospective trial was randomised, double-blind and placebo-controlled and was crossed-over after three cycles. Although the results showed an improvement in symptoms of PMS during the trial, no significant differences in the scoring between the active and placebo groups were found over six cycles. No "carry-over" effect of active medication was observed; the beneficial effect on all symptoms (psychological, fluid retention, breast) was rapid, the scores decreasing in the first cycle but increasing slightly at the change-over period after the third cycle, irrespective of whether the active or placebo medication was next given. These findings indicate that the improvement experienced by these women with moderate PMS was solely a placebo effect.