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Microbicide Products Enter Human Trials -- May 15, 2000

In many countries around the world, scientists are working on experimental products similar to contraceptive spermicides -- new products a woman can use to protect against HIV infections and other sexually transmitted diseases (STDs).

More than 50 experimental substances are being studied for these new products, called "microbicides." Many of them are in the early stages of clinical trials among female volunteers, according to the current issue of Family Health International’s Network, an international quarterly health bulletin.

Nevertheless, this group of experimental products to protect against HIV and other STDs is many years away from being available for general use. When they do become available, the first products are likely to provide only limited protection against infections.

Meanwhile, experts say that correct and consistent use of the male latex condom provides the most effective protection against STDs. Consistent use means that a condom is used with every act of sexual intercourse.

For couples who do not use condoms consistently and correctly, a safe and effective microbicide would offer an alternative method of protection. But how soon these products can be developed is anyone’s guess. "At this point, we just do not know which substance will turn out best," says Dr. Zeda Rosenberg, scientific director of FHI’s HIV Prevention Trials Network, a research project involving FHI and other institutions to evaluate HIV prevention interventions, including microbicides.

"All of these substances are active against microorganisms in the laboratory, and some animal studies and human safety trials are promising," she says. "But we still need more information" about the effectiveness of experimental products. A variety of other issues are also important to study, such as whether couples will find a particular product acceptable to use.

In addition to new microbicide products being studied worldwide, other research is examining whether existing contraceptive spermicides prevent STDs. These products to prevent pregnancy, available for decades, have already undergone extensive studies involving safety and other issues.

Consequently, if the active ingredients in spermicides can protect against STDs, they may be available for general use sooner than experimental microbicide products. Commercially available spermicides typically use one or more of three active ingredients: nonoxynol-9, benzalkonium chloride or octoxynol-9. A woman applies a spermicide before intercourse, and the active ingredient prevents pregnancy by killing the man’s sperm cells upon contact.

Some of the experimental microbicide products being developed work the same way as spermicides -- by killing or disabling disease cells (bacteria or viruses) upon contact.

Other experimental microbicides work either by blocking passage of a disease cell from one person to another or by preventing disease cells that enter another person’s body from multiplying.

In addition to disease protection, there are many features that would be desirable in a microbicide product. For example, microbicides that do not prevent a pregnancy would be important to women who need protection from STDs but wish to conceive. About 15 products under study do not seem to harm sperm, making them likely candidates for a noncontraceptive microbicide.

Scientists are also looking for products that could protect someone from HIV or other STDs even when applied soon after intercourse, just as emergency contraceptive pills can be used within 72 hours of intercourse to reduce the risk of pregnancy.

Clinical studies among volunteer women to examine the safety of experimental microbicides have taken place or are planned in the United States, the United Kingdom, Finland, Brazil, Chile, the Dominican Republic, Côte d’Ivoire, Malawi, South Africa, Uganda, Zimbabwe, Australia, India and Thailand.