Absorption, Bioavailability, and Partner Transfer of Estradiol from a Topical Emulsion

STUDY OBJECTIVE: To investigate the systemic absorption of estradiol in partners of postmenopausal women after making skin-to-skin contact with the application sites of estradiol topical emulsion. DESIGN: Open-label, nonrandomized clinical study. SETTING: Clinical study unit. SUBJECTS: Fourteen postmenopausal women and their male partners (mean +/- SD age 57.6+/-8.7 and 49.1+/-13.3 yrs, respectively). INTERVENTION: Women applied 1.74 g/day of estradiol topical emulsion (containing 2.5 mg estradiol/g) to each leg on 2 consecutive days. Their male partners were exposed to the application sites by mean of vigorous skin-to-skin contact at 2 and 8 hours after application. MEASUREMENTS AND MAIN RESULTS: Serum concentrations of estradiol, estrone, and estrone sulfate were measured in the female subjects and their male partners. The mean +/- SD estradiol level in the women at baseline was 2.9+/-1.5 pg/ml. Their average concentration (C(average)) increased from 15.3+/-14.8 pg/ml on the first day of treatment to 27.6+/-22.7 pg/ml on the second day. Among male partners, C(average) for serum estradiol increased from 17.0+/-4.3 pg/ml at baseline to 21.0+/-4.4 pg/ml on the second exposure day. Their geometric mean fold ratio for the area under the serum concentration-time curve from 0-24 hours was 1.25 (baseline vs after second exposure, p<0.0001). CONCLUSIONS: Estradiol was transferred to male partners by means of vigorous skin-to-skin contact at application sites. Although the increase in postexposure levels of estradiol was statistically significant, all levels were still below the upper limit of the normal range for men (45 pg/ml).