Compatibility between the spermicide nonoxynol 9 and mid-cycle human cervical mucus.

The rate of diffusion of [125I]-nonoxynol 9 into mid-cycle human cervical mucus was measured and found to be negligible compared with D-glucose (used as an uncharged small molecule for comparison with nonoxynol 9). These data were confirmed by observation of the lack of inhibition of the movement of spermatozoa in mucus that had been in surface contact, for 3 hours, with a concentration 30 times greater than the ED100 of nonoxynol 9. These results show that the entry of nonoxynol 9 into mucus could be minimal under conditions that would exist in vivo and highlights a limitation of this compound as a vaginal contraceptive.