The FDA yesterday proposed a new label for over-the-counter contraceptives that contain the spermicide nonoxynol-9, warning that the substance does not protect against HIV or other sexually transmitted diseases and may increase the risk of HIV and STD transmission, according to an agency press release. The proposed labeling is based on recent studies examining nonoxynol-9, including recently published data from a World Health Organization study of 991 HIV-negative sex workers in Africa and Thailand, which found that nonoxynol-9 is ineffective at preventing HIV infection. The spermicide works as a vaginal contraceptive by damaging the cell membranes of sperm, and some laboratory evidence shows that nonoxynol-9 damages the cell walls of some organisms that cause STDs and is active against some bacteria and viruses. According to data presented in the labeling proposal, the FDA believes that nonoxynol-9's membrane-damaging effect can also harm the cell lining of the vagina and cervix, possibly increasing the risk of STD and HIV transmission in women who use the spermicide. The proposed warning label is published in the Jan. 16 Federal Register, and the FDA is allowing a 90-day public comment period on the statements and the most appropriate way of presenting the new warning (FDA release, 1/16).