PURPOSE: Hot flashes are common experience for menopausal women, and for many, 
are severe enough to significantly compromise their overall sense of well being 
and quality of life. The aim of this study was to compare the efficacy of 
evening primrose with placebo in improvement of menopausal hot flashes.
METHODS: In a 6-week randomized clinical trial, a total of 56 menopausal women 
aged 45-59 years were participated in this study. The patients were asked for 
their hot flashes characteristics and responded to HFRDIS (hot flash related 
daily interference scale) questionnaire before and after the intervention. The 
participants were randomly assigned to take two capsules per day (totally 90 
capsules for 6 weeks) of placebo or evening primrose (500 mg) for continuous 6 
weeks. Then, the improvement in hot flashes was compared between two groups.
RESULTS: The percent of improvement in hot flash frequency, severity and 
duration were 39, 42 and 19 %, in evening primrose group compared with 32, 32 
and 18 % in placebo group, respectively. Although all three characters of hot 
flash was ameliorated in evening primrose arm, only its severity was 
significantly better in this arm compared with placebo group (P < 0.05). All 
HFRDIS score were significantly improved in two groups, but the percentage of 
improvement in social activities, relations with others, and sexuality was 
significantly superior to placebo group (P < 0.05).
CONCLUSIONS: The application of oral evening primrose oil compared with placebo 
for controlling hot flashes may decrease more the intensity of attacks as well 
as ameliorating the HFRDIS score.