AbstractObjective:To evaluate secondary exposure of testosterone transferred to females from a male partner, dosed with 1.62% testosterone gel after direct skin-to-skin contact with the application site, and to investigate the effect of wearing a t-shirt on testosterone transfer.Research design and methods:Across three studies, a total of 72 healthy males applied 5.0 g 1.62% testosterone gel to their abdomen alone, upper arms/shoulders alone, or a combination of their upper arms/shoulders and abdomen (single dose or once daily for 7 days). Male–female contact occurred 2 or 12 hours after testosterone gel application, with males either wearing or not wearing a t-shirt. There were 15 minutes of supervised contact with the application site between the male and his female partner. Blood samples were collected over a 24 hour period in females for assessment of serum testosterone levels at baseline and after contact.Main outcome measures:Pharmacokinetic parameters included Cmax(maximum serum concentration), AUC0–24(area under the serum concentration–time curve from 0–24 hours), and Cav(time-averaged concentration over the 24-hour period post-contact). Subjects were monitored for adverse events.Clinical trial registration NCT numbers:Study 1 was not registered (first subject enrolled 8 March 2007); Study 2: 00998933; Study 3, 01130298.Results:Testosterone levels (Cavand Cmax) in females increased 86–185% from baseline after direct abdominal skin contact, although Cavlevels remained within female eugonadal range. Testosterone concentrations returned to baseline within 48 hours after last skin contact. A t-shirt barrier reduced testosterone transfer by approximately 40–48% when 5.0 g of testosterone gel was applied to the abdomen alone. A t-shirt barrier prevented transfer when 5.0 g of testosterone gel was applied to the upper arms and shoulders or to a combination of the upper arms and shoulders and the abdomen (Cmaxand Cavincreased by approximately 5–11%). No major safety events were observed during the studies.Conclusions:There is a risk of testosterone transfer from males using 1.62% testosterone gel to others who come in contact with the application site for at least 12 hours after application. Secondary exposure can be mitigated by means of a t-shirt barrier.Study limitations:Women for these studies were not selected by menopausal status. The study designs were intended to simulate exaggerated conditions of transfer. [ABSTRACT FROM AUTHOR]