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Nonoxynol-9

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Public Policy Documents on Nonoxynol-9: Updated in April 2005

Nonoxynol-9 (or N-9) is the active ingredient in most over-the-counter birth control products available in the United States, Canada and Europe. Contraceptive jellies and creams (such as those used with the diaphragm), Conceptrol suppositories, Delfin foam, Vaginal Contraceptive Film (VCF), Encare Oval suppositories and Advantage-S gel are all products that contain N-9. These products work as contraceptives because the N-9 disrupts the sperm's outer membrane, thereby deactivating it.

N-9 products were designed and approved by the FDA as contraceptives, not as microbicides. But, since N-9 kills HIV and a wide variety of other STI pathogens in the test tube, the idea of using it for disease prevention has been around for decades.

Nonoxynol-9 provides little, if any, protection against bacterial STIs such as chlamydia and gonorrhea.

Until recently, scientists believed that vaginal use of nonoxynol-9 offered some --albeit limited-- protection against bacterial STIs such as gonorrhea and chlamydia.

Recent evidence, however, has called into question even modest claims of protection. Three randomized controlled trials have failed to detect any statistically significant effect of N-9 against common bacterial STIs (Roddy et al. 1998; Van Damme 2000; Roddy et al. 2002). As a result, the US Centers for Disease Control and the World Health Organization have concluded that products containing N-9 should not be promoted for STI protection.

N-9 also provides no protection against HIV.

Early hopes that N-9 might be effective against HIV proved to be false. When scientists first began looking for vaginal microbicides, they decided to first evaluate whether any existing products might work for this purpose. They began testing existing spermicides containing N-9 to see if they prevented HIV transmission when used in the vagina.

After a long and complicated history of testing, scientists have concluded that products containing N-9 do not offer protection against HIV. It appears that when used frequently, N-9 containing products may increase risk of HIV transmission by causing small disruptions in the vaginal epithelium (cell wall). Scientists are concerned that these disruptions may increase a woman's risk of acquiring HIV. More on the history of N-9 testing...

The fact that N-9 does not work as a microbicide is disappointing, but says nothing about the feasibility of microbicides in general.

Although it would have been nice if N-9 worked as a microbicide, it was designed as a contraceptive not as an anti-HIV agent. Testing of N-9 was based on the hope that it might offer some protection, while scientists worked to identify and test a new generation of products.

Some people have assumed that because N-9 did not work as a microbicide that the entire concept of anti-infective microbicides has been proven not to work. This conclusion is wrong and misleading.

Saying that the concept won't work just because one product lead has shown to be ineffective is like saying that combination therapy to suppress HIV replication doesn't work because one early drug trial failed to show positive results.

The N-9 clinical trials do not suggest that effective microbicides cannot be found -- only that Nonoxynol-9 probably is not one of them. Dozens of product leads are now in the research pipeline and most work by mechanisms of action entirely different from that of Nonoxynol-9.

Is it safe for women to continue using N-9 containing products for birth control?

Evidence suggests that it is safe for women at low or no risk of HIV to continue to use spermicides containing N-9 for birth control purposes. Women who may be at risk of HIV and who plan to use the product more than once a day should consider switching to another form of birth control.

Apparently, the irritating effects of N-9 are dependent on dose and frequency of product use. Studies that have looked specifically at vaginal irritation have demonstrated that epithelial disruption is related to the frequency of product use, with lower dose products (52-150 mg.) causing little or no disruption when used once a day or less (Niruthisard 1992; Roddy 1993; Stevens et al. 1996).

Surprisingly, the sensation of "irritation" does not correlate well with actual microscopic or laboratory evidence of epithelial disruption. Thus, not all women who experience "irritation" actually have epithelial disruption or inflammation. Likewise, a woman may have lesions or disruption but not experience a sensation of irritation.