Research efforts are currently under way to develop safe and effective topical gel or cream products or suppositories, called microbicides, that can be inserted into the vagina or rectum to prevent or minimize the risk of being infected with HIV and other STIs. These products would be applied before sexual intercourse, but they would not be a substitute for condoms. Rather, they would provide extra protection at low cost. In the developing world, where financial resources are limited and women are often unable to depend on male cooperation, microbicides would offer an especially benefi­cial option for STI prevention (Mahan et al., 2011).

Technically, the term microbicide means "a product that kills microbes." However, there are several ways that microbicide products could function to prevent STIs. Some microbicides would kill or destroy infection-causing organisms present in semen or vag­inal secretions. Other microbicides under development would work not by destroying an infection-causing pathogen but by blocking its entry or fusion with target cells or by stopping its replication once inside target cells.

chapter 15

Several microbicide candidates are currently being studied in clinical trials with large study populations in developing countries that are at risk for infection by HIV and other STIs (Stadler & Saethre, 2011). The National Institutes of Health (2009) issued a report on a large-scale clinical trial of a microbicide known as PRO 2000 that was conducted with several thousand women in Africa and the United States. Although the findings of this study indicate that PRO 2000 may effectively protect women against HIV infection, more data are necessary to conclusively determine the effectiveness of this microbicide candidate.

The effectiveness of microbicide products is related to adherence to or consistency of use. This connection was revealed in the PRO 2000 study in which only about 60% of the enrolled subjects reported using the microbicide gel during every sexual act (Hei – sea et al., 2011).

Unfortunately, a recent research trial in Africa found that a vaginal gel microbicide containing the antiretroviral drug tenofovir was no more effective than a placebo gel in preventing HIV infection (Friedrich, 2012).

Some of the products under investigation have both spermicidal and antimicrobial capabilities. Health officials hope to eventually have effective products from both cat­egories, because some users will want protection against both unwanted pregnancies and STIs, whereas others will seek only protection against infection. We hope that one or more of these much-needed products will be available soon.