HIV infection and AIDS continue to spread worldwide, and women account for an estimated 50 percent of those infected. Unprotected heterosexual vaginal intercourse is an important source of new cases. Condoms are widely recognized as effective in prevention, but their availability has not stopped the pandemic. This method is controlled by the male partner. It would be beneficial to have a safe, effective prevention method that is controlled by the female partner. A recent medical review article reports that women around the world face social, economic, and legal disadvantages which limit their ability to protect themselves from sexually transmitted infections using currently available means.
A promising approach is microbicidal drug products designed for vaginal use. Ideally, the same product could kill pathogenic microbes that cause several different, common sexually transmitted infections. Issues in the development of these products include the drug delivery system and the choice of drug. The review article reports that 50 drug candidates were in preclinical development as of late 2008. An update posted online in October 2009 reports 11 of these in clinical trials.
Drugs already on the market for vaginal use include treatment for yeast infection. Researchers also recognize the potential of vaginally administered drugs for systemic use. Oral drugs have the disadvantage of “first pass metabolism” because everything absorbed from the intestines goes to the liver first. Skin patches are available for some drugs in order to reach their targets with less of the dose metabolized by the liver. The vagina has an excellent blood supply and large surface area that can be used for drug absorption. Thus, anti-HIV drugs administered vaginally have a double potential for killing the virus with minimal side effects.
Most drug delivery systems for vaginal use are in the form of gels or ointments. These may not be optimum for HIV prevention. Women in clinical trials report negative experiences with the products leaking or dripping. Alternate systems include vaginal rings, currently used for contraception, and films.