A pilot study of the comparative bioavailability of estradiol from two different estradiol transdermal systems: Oesclim ® 50 and Systen ® 50

Abstract

The bioavailability of estradiol from Oesclim ® 50 and Systen ® 50, two matrix-type estradiol transdermal systems with the same nominal delivery rate of 50 μg per 24 hours, was compared in a randomized, crossover pilot study of 12 healthy postmenopausal women. A 7-day washout separated the two 4-day application periods. Serum estradiol levels were determined by using radioimmunoassay before application of the transdermal system and at defined intervals thereafter. Higher serum estradiol levels were observed with Oesclim 50 than with Systen 50. Analysis of log-transformed, baseline-corrected pharmacokinetic values showed significant differences between the two transdermal systems. Except for the maximum serum concentration and concentration at 72 hours, all Oesclim 50 pharmacokinetic values were significantly higher than those of Systen 50 ( P < 0.05). Estradiol bioavailability was approximately 1.5 to 2 times higher after application of Oesclim 50 than after application of Systen 50.