Women currently have a robust variety of birth control options. Now advances in microbicide gels that can be applied to the vagina raise the possibility of providing women greater choices when it comes to preventing the spread of HIV.
A microbicide gel containing the antiretroviral drug tenofovir had a 39% success rate in protecting women from acquiring HIV from their sexual partners, according to results released last year from a clinical trial in South Africa. Though the success rate is relatively low, a microbicide may appear on the market within a few years, pending other studies of the gel's effectiveness. Scientists are hopeful that further advances in the microbicide's composition will improve the success rate, providing women with the first form of protection they can use against infection.
'Tenofovir gel could fill an important HIV prevention gap by empowering women who are unable to successfully negotiate mutual faithfulness or condom use with their male partners,' study co'principal investigator Quarraisha Abdool Karim, Ph.D., told Science Daily.
A further microbicide trial under way, known as VOICE, is comparing the effectiveness of tenofovir gel versus oral pre-exposure prophylaxis (PrEP)'the use of antiretroviral pills to prevent HIV transmission. Results from that study are expected by 2013.
Even though researchers expect that a PrEP regimen might be approved before the tenofovir gel, the gel still has advantages. Since the drug contained in the gel remains in the vaginal tissue, it's unlikely that a woman who becomes infected while using the gel would develop a drug-resistant form of the virus. And microbicides show promise in preventing other sexually transmitted diseases, including genital herpes.
Scientists are also working to develop a rectal microbicide gel, designed for the 95% of gay men and 40% of heterosexual women who have engaged in anal sex at least once during their lifetime. Because tissues in the rectum are more fragile than vaginal tissue, a different type of gel is needed. Large-scale human trials for a rectal gel are not expected to begin for another two to three years, according to The New York Times.