More Bad News About Commonly Used Spermicide
The widely used spermicide nonoxynol-9 (N-9) was found to enhances genital transmission of human papillomavirus (HPV) in an animal model:
"The findings add to the growing list of why it is preferable to recommend alternative contraceptives to N-9 spermicides," Dr. John T. Schiller from National Cancer Institute, Bethesda, Maryland told Reuters Health. "Others are that they are not particularly effective and may increase the risk of HIV infection."
Dr. Schiller and associates used a mouse model of cervicovaginal infection with HPV16 to investigate the effects of nonoxynol-9 and carrageenan on genital transmission of HPV.
Both N-9 and an over-the-counter spermicide that contains 4% N-9 sensitized the genital tract to HPV infection, the authors report.
N-9 treatment was associated with disruption of the epithelium which allowed viral capsids to enter and bind to the basement membrane.
In contrast, carrageenan prevented infection in the genital mucosa rendered susceptible to infection by either mechanical disruption or chemical disruption with N-9.
Dr. Schiller said that his team is working with the NCI's Division of Cancer Prevention to initiate a placebo-controlled trial of carrageenan as a topical microbicide to prevent HPV infection in women.
"If a trial confirmed broad spectrum activity against genital HPV types, carrageenan might become a useful adjunct to the current prophylactic HPV vaccines, which target a narrower spectrum of genital HPVs," the investigators write. "Because spermicidal activity of N-9 is retained in carrageenan-based gels, carrageenan might also be considered as a protective additive in over-the-counter vaginal contraceptives."
However, note this:
"We actually don't want to overly discourage the use of N-9 containing spermicides at this point, if a woman doesn't have other choices at hand," Dr. Schiller said. "This is because unwanted pregnancy will be more of problem than unwanted HPV infection for most women."