Effect of St John's wort on severity, frequency, and duration of hot flashes in premenopausal, perimenopausal and postmenopausal women: a randomized, double-blind, placebo-controlled study.

OBJECTIVE: Because of a decline in estradiol levels, premenopausal, perimenopausal, and postmenopausal women experience symptoms related to vasomotor instability. Certain plants have been found to have molecular components that are identical in structure and function to human hormones. We conducted this study to compare the efficacy of St John's wort with that of placebo in women with hot flashes. METHODS: A total of 100 women participated in a clinical trial conducted in an academic medical center in Shiraz-Iran. Women were treated with St John's wort extract or placebo for 8 weeks. Climacteric complaints were evaluated by using the Blatt-Kupperman Index at two follow-up visits. Statistical analysis was carried out by using descriptive statistics and multivariate analysis. RESULTS: The mean age of the participants was 50.4 years. Both groups responded to the interventions, and the within-group differences in frequency, duration, and severity of hot flashes were statistically significant (P < 0.05). The difference in duration of hot flashes between groups was not significant on the 4th week of intervention (P = 0.27); however, it was statistically significant between the two groups on the 8th week of treatment (P < 0.001). The fall-off in frequency of hot flashes on the 4th and 8th weeks of intervention was more evident in women receiving St John's wort, and the differences between groups were statistically significant (P = 0.005 and P < 0.001, respectively). Furthermore, comparing both study groups, we showed that the decrease in the severity of flashes in women who received St John's wort was more evident on the 4th and 8th weeks (P = 0.004 and P < 0.001, respectively). CONCLUSIONS: St John's wort can be used as an effective treatment for the vasomotor symptoms of perimenopausal or postmenopausal women.