Comparative bioavailability study of a matrix versus a reservoir transdermal estradiol patch in healthy postmenopausal women

Abstract

The single-application bioavailability of estradiol from a new matrix (Climaderm ®) versus a standard reservoir (Estraderm ® TTS 50) transdermal therapeutic system was investigated in a prospective, open-label, randomized, two-period crossover study in healthy postmenopausal volunteers. Each system was labeled to deliver approximately 0.05 mg of estradiol per day and was applied to the abdominal area and worn continuously for 4 days; there was a minimum 5-day washout between the two study periods. For each study period, venous blood samples were obtained before patch application, during treatment (20 samples), and after patch removal (3 samples) and assayed for estradiol and estrone. In addition, the samples obtained at 0, 8, 12, 24, 48, 72, 96, and 120 hours after application were assayed for follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Twenty-six women completed both study periods. No differences between the patches were detected with regard to peak concentration and time to peak concentration. Based on area under the curve, the two patches were bioequivalent through 48 hours. From 48 to 96 hours, however, the matrix patch produced a more consistent level of estradiol. Mean values for the levels of estradiol, estrone, FSH, and LH for the entire study period are presented.