BACKGROUND: The most common complaints during climacteric are vasomotor 
symptoms. A circadian rhythm has been observed when hot flashes start; however, 
not much information is available in this field.
AIMS: To analyze whether the time (morning/evening) of administration of a 
compound containing 60 mg of dry soy seed extract (glycine max) with 40% of 
total isoflavones, primrose oil and α-tocopherol modifies the effect on the 
climacteric syndrome.
TRIAL DESIGN: Multicentric, observational, open, prospective, longitudinal and 
cross-sectional study. Subjects and methods. One thousand six hundred eighty-two 
postmenopausal women with climacteric symptoms were allocated in two groups in 
order to receive the treatment in the morning (Group 1) or in the evening (Group 
2), switching administration time after 3 months. Clinical evaluation was 
carried out at 0, 3 and 6 months of follow-up using Blatt-Kupperman and Greene 
scales.
RESULTS: 233 (13.9%) women dropped out from the study. Both administration times 
improved the climacteric symptoms after 3 and 6 months of treatment, showing a 
reduction in the scores of Blatt-Kupperman and Greene scales (p < 0.001). No 
differences between both groups during the follow-up were identified.
CONCLUSIONS: The time of administration of isoflavones does not modify its 
effect on climacteric symptoms.