Each Imvaggis pessary contains 30 microgram estriol. One is administered once daily at bedtime for 3 weeks, then twice weekly for maintenance treatment.
In a double-blind, placebo-controlled trial, 436 postmenopausal women with vaginal atrophy were randomised to use pessaries containing 200 microgram estriol, 30 microgram estriol or placebo once daily for 20 days, then twice weekly for a further 9 weeks. The primary efficacy endpoints were increase in vaginal maturation index, decrease in vaginal pH and decrease in intensity of most bothersome symptom.
At week 12, a significantly greater increase in vaginal maturation index was seen in women who used 200 microgram or 30 microgram estriol (46.3 and 38.4, respectively) than in those who used placebo pessaries (23.9; p < 0.001 for both comparisons).
Moreover, compared with the placebo group, the 200 microgram and 30 microgram estriol groups showed significantly greater decline in vaginal pH (−1.6 and −1.4, respectively, vs −0.6; p < 0.001 for both comparisons) and in intensity of most bothersome symptom (−52.2 and −47.1, respectively, vs −31.8; p < 0.001 for both comparisons).
Although there were indications of slightly better effectiveness with 200 microgram estriol, 30 microgram was sufficient to achieve statistically significant and clinically relevant improvement in all efficacy variables.
Another study evaluated the bioavailability of the 30 microgram estriol pessary in 19 postmenopausal women with vaginal atrophy who were treated daily for 21 days. The study found that a single administration resulted in a very low systemic bioavailability, which decreased even more after multiple dosing.
The low-dose estriol pessary was well tolerated in both studies. The most commonly reported adverse events were headache, local irritation and vaginal discharge.