Diffusion of nonoxynol-9 into human semen in vitro

The diffusion of [125I]-nonoxynol-9 into human semen was investigated in vitro before and after liquefaction. No significant difference was found in the distribution of [125I]-nonoxynol-9 within columns of preliquefied semen, liquefied semen, seminal plasma, or water after < or = 120 minutes of diffusion; however, significantly more nonoxynol-9 entered preliquefied semen. The concentration of nonoxynol-9 that entered semen in vitro was greater than its ED100 and the bioavailability was confirmed by demonstration of the retention of spermicidal action. These results indicate that the gel state of preliquefied semen does not inhibit the entry or action of nonoxynol-9 and, consequently, sperm would be exposed to it immediately when it is used in vivo as a vaginal spermicide.