Microbicides are compounds that can be applied inside the vagina or rectum to protect against sexually transmitted infections (STIs) including HIV. They can be formulated as gels, creams, films, or suppositories. Microbicides may or may not have spermicidal activity (contraceptive effect). At present, an effective microbicide is not available.

There are different ways in which microbicides act to prevent infection with genital pathogens. Some microbicides (e.g Carraguard®, Cyanoviran®, cellulose sulphate, PRO 2000®) provide a physical barrier that keeps HIV and other pathogens from reaching the target cells. Another class of microbicides