OBJECTIVE: To evaluate the efficacy of gamolenic acid provided by evening 
primrose oil in treating hot flushes and sweating associated with the menopause.
DESIGN: Randomised, double blind, placebo controlled study.
SETTING: District general hospital and teaching hospital.
SUBJECTS: 56 menopausal women suffering hot flushes at least three times a day.
INTERVENTION: Four capsules twice a day of 500 mg evening primrose oil with 10 
mg natural vitamin E or 500 mg liquid paraffin for six months.
MAIN OUTCOME MEASURES: Change in the number of hot flushes or sweating episodes 
a month.
RESULTS: 56 diaries were analysed, 28 from women taking gamolenic acid and 28 
from those taking placebo. Only 18 women given gamolenic acid and 17 given 
placebo completed the trial. The mean (SE) improvement in the number of flushes 
in the last available treatment cycle compared with the control cycle was 1.9 
(0.4) (P < 0.001) for daytime flushes and 0.7 (0.3) (P < 0.05) for night time 
flushes in women taking placebo; the corresponding values for women taking 
gamolenic acid were 0.5 (0.4) and 0.5 (0.3). In women taking gamolenic acid the 
only significant improvement was a reduction in the maximum number of night time 
flushes (1.4 (0.6); P < 0.05).
CONCLUSION: Gamolenic acid offers no benefit over placebo in treating menopausal 
flushing.