Interpersonal testosterone transfer after topical application of a newly developed testosterone gel preparation

Transdermal testosterone gel treatment is an effective androgen substitution therapy with several advantages over conventional substitution therapies. Whereas side-effects due to overdosing of hypogonadal patients are unlikely, testosterone gel application without protection may cause severe side-effects in other subjects (partners, family members) by contamination. Therefore, the risk of testosterone transfer of a newly developed 2.5% testosterone gel preparation was evaluated.

In two clinical randomized open single-centre studies on healthy male volunteers the percentage of testosterone remaining on the skin after gel application over time (n = 12) and the possibility of a transfer of testosterone to another person (n = 28) was evaluated. In the second study the endogenous testosterone production in the receiving subjects was suppressed by injecting 400 mg norethisterone enanthate (NETE).

After 8 h approximately 60% of testosterone applied to the skin could be recovered. When the skin had been previously washed with water, only about 14% of applied testosterone could be recovered. After intense skin contact with a volunteer who had applied testosterone before on his forearm, no increase in testosterone serum levels could be found in NETE-suppressed men.

Although considerable amounts of testosterone remain on the intact skin for several hours after evaporation of the alcohol vehicle, contamination of a second, especially female or prepubertal, subject causing side-effects seems very unlikely.