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Nonoxynol-9 (N-9)


Updated July 30, 2012

Nonoxynol-9 (N-9)

Spermicides with N9

Photo © 2010 Dawn Stacey

Nonoxynol-9 (N-9) is a chemical detergent and can be found in many common spermicides. It has been used for contraception purposes since the 1950s. N-9 works by damaging sperm cell membranes. By breaking these outer barrier membranes, N-9 immobilizes and kills sperm. Once the sperm are destroyed, they are no longer able to fertilize an egg.

Spermicides that contain N-9 can be used as:

Although the U.S. Food and Drug Association (FDA) recognizes that N-9 has been shown in laboratory studies to be an active against some STD-causing bacteria and viruses by damaging the cell walls of STD causing pathogens, the agency cautions people about using this spermicide for that purpose. So, in 2007, the FDA issued a labeling change -- manufacturers of over-the-counter spermicide products that contain N-9 must now include a warning statement that the chemical Nonoxynol-9 (N9) does not provide protection against infection from HIV or other sexually transmitted diseases.

The official stance of the Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and the FDA is that N-9 is a safe, effective contraceptive option for women who are at low risk for HIV/STDs as long as they do not use N-9 more than once a day. This is based on research that when used frequently or in high dosages, N-9 may cause cell damage to vaginal skin cells or cause inflammation of the vagina and/or cervix. The WHO further explains that repeated and/or high-dose use of N-9 is associated with increased risk of vaginal lesions (abnormal tissue changes) -- this damage could potentially increase a woman’s risk for contracting HIV/STDs during vaginal sex. Because N-9 can also disrupt cervical mucus, viral shedding can be increased, making it easier for a woman to transmit HIV/STDs to her partner. These types of vaginal irritations can also make a woman more susceptible to urinary tract infections. Studies also show that N-9 may cause even more damage when use rectally.

The FDA also requires that spermicides that contain N-9 warn that nonoxynol-9 is for vaginal use only (not for rectal/anal use). Labels also must state that use of N-9 may increase the risk of getting HIV from an infected partner, and that you should not use N-9 if you or your sexual partner has HIV/AIDS. Finally, N-9 product labels caution that you may experience vaginal irritation (burning, itching, or a rash) when using these products.

Pronunciation: Nonoxynol-9: /non·ox·y·nol 9/; non-ok´sĭ-nol nīn
Also Known As: N-9, N9, Spermicide

N-9 is a chemical found in spermicide; because it can cause vaginal irritation, a woman should not use products containing N-9 more than once a day.


Centers for Disease Control and Prevention. U.S. Medical Eligibility Criteria for Contraceptive Use, 2010. MMWR Early Release 2010;59 May 28:1-86.

Department of Health and Human Services, Food and Drug Administration. (2007). Over-the-counter Vaginal Contraceptive and Spermicide Drug Products Containing Nonoxynol9; Required Labeling.[Docket No. 1980N-02801]:1-61a.

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