Steady-state pharmacokinetics following application of a novel transdermal estradiol spray in healthy postmenopausal women

This study was designed to evaluate the steady-state pharmacokinetics (PK) of estradiol and its metabolites, estrone and estrone sulfate, following application of a novel estradiol transdermal spray to healthy postmenopausal women. Participants were randomly assigned in parallel to receive 1-, 2-, or 3-spray doses (24 participants/dose level) of a 1.7% estradiol metered-dose transdermal spray (1.53 mg/spray) once daily for 14 days. Blood was collected predose on days 1 to 14 and over 7 days after the last dose. Serum concentrations for all 3 analytes reached steady state by day 7 or 8 and were still slightly above baseline on day 21. Estradiol, estrone, and estrone sulfate serum concentrations generally increased with increasing dose. Mean estradiol and estrone maximum serum concentration (C_max) following 1, 2, or 3 sprays for 14 days were 36 and 50, 57 and 60, and 54 and 71 pg/mL, respectively. Estradiol time when maximum concentration occurred (t_max) was 18 to 20 hours. The area under the serum concentration-time curve over 24 hours following the last dose of study drug (AUC_{0-24 h} ) on day 14 for the 1-, 2-, and 3-spray groups, respectively, was 471, 736, and 742 pg·h/mL for estradiol; 886, 1208, and 1367 pg·h/mL for estrone; and 16 501, 26 515, and 27 971 pg·h/mL for estrone sulfate. The metered-dose estradiol transdermal spray delivers estradiol at therapeutic levels and produces low serum estrone concentrations.