Vaginal absorption of two estriol preparations: A comparative study in postmenopausal women

Abstract

In a comparative randomized cross-over study the absorption of a single dose of 0.5 mg estriol from a vaginal cream or a vaginal suppository (Ovestin^R, Organon, The Netherlands) was studied. Eight healthy postmenopausal women participated and the preparations were given with an interval of 14 days. Blood sampling was performed twice before application and then after 1/4, 1/2, 1, 2, 4, 6, 8, 24 and 48 hours. Serum was analysed for unconjugated and conjugated estriol (E₃), FSH and LH by radio-immunoas-say. Considerable interindividual variations in serum levels of unconjugated E₃ were found but mean values were about equal throughout the study for the two preparations. Peak levels of 0.5 — 0.6 nmol/1 were achieved 1 — 2 hours after application of the preparations and after 24 hours no unconjugated E₃ was measurable. Conjugated E₃ rose rapidly but within 48 hours serum concentrations reached baseline levels. A maximum decrease in serum LH levels of about 40% was obtained with both preparations after 6 hours and the return to baseline within 24 hours indicates a relationship to unconjugated E₃. FSH in serum was maximally suppressed 6—12%. Estriol is thus readily absorbed by the vaginal route and peak levels of unconjugated E₃ after insertion of 0.5 mg estriol seem to be comparable to those obtained after 8-12 mg estriol given orally.