Preventive effect of oral estetrol in a menopausal hot flush model.

OBJECTIVE: To evaluate the efficacy of estetrol (E(4)) in alleviating hot flushes in an experimental animal model considered representative for menopausal vasomotor symptoms.
METHODS: Recording of the thermal responses in the tail skin of morphine-dependent ovariectomized rats after morphine withdrawal by administration of naloxone. Six groups of rats were treated orally for 8 days as follows: vehicle (negative) control; E(4): 0.1, 0.3, 1.0 and 3.0 mg/kg/day; and, as active (positive) control, ethinylestradiol 0.3 mg/kg/day. On day 8, tail skin temperature was recorded at baseline and for 60 min at 5-min intervals following naloxone administration. Results In control animals, tail skin temperature increased sharply by about 4.5 degrees C after naloxone treatment and reverted to baseline by 60 min. Estetrol suppressed the tail skin temperature increase in a dose-dependent fashion. The highest dose of E(4) tested (3 mg/kg/day) was equipotent to a 10-fold lower dose of ethinylestradiol. Both fully suppressed tail skin temperature changes.
CONCLUSION: Estetrol is effective in alleviating hot flushes in an experimental animal model considered representative for studying menopausal hot flushes (vasomotor symptoms). In this model, the potency of estetrol is 10-fold lower compared to ethinylestradiol.