Current or proposed clinical trials involving more than 20,000 volunteers around the world will soon help answer important questions about the use of pre-exposure prophylaxis (PrEP) to prevent sexual HIV transmission. That was the message of Myron S. Cohen, MD, FIDSA, professor of medicine, microbiology, and public health at the University of North Carolina at Chapel Hill, during the “State of the Art in HIV Treatment” symposium at the 47th Annual Meeting of IDSA in Philadelphia. Encouraging results in animal studies to date have led to great interest in this approach and its potential to slow the HIV/AIDS pandemic.
One of the research efforts, the Global iPrEx study, is an ongoing Phase III trial determining whether the use of a single daily antiretroviral pill, emtricitabine/tenofovir disoproxil fumarate, can prevent HIV infection among a population of approximately 2,400 adult men who have sex with men. The trial includes sites in the United States, Peru, Ecuador, Brazil, South Africa, and Thailand.
Other studies are examining the use of topical antiretroviral gels to prevent infection in women. A Phase IIb trial of a tenofovir gel in South Africa, involving 980 women, has been ongoing since 2007, Dr. Cohen said, and results are expected in 2010. Another strategy currently in Phase I and II trials uses a vaginal ring impregnated with an antiviral agent, dapivirine, allowing the drug to be delivered over as many as 30 days, potentially offering extended protection from HIV infection and the possibility of combining birth control drugs in the same device.
Dr. Cohen also discussed the use of antiretrovirals to prevent infection post-exposure and the concept of using of HIV treatment of infected individuals as a preventive tool, in addition to aggressive “test and treat” efforts at the community level. Antiretroviral agents will be used as part of prevention efforts, he predicted, but precisely how, for whom, and with what degree of benefit are questions that remain to be answered by further research. “These are the unknowns that will be resolved in the next five years,” Dr. Cohen added.
Drug Interactions and Antiretrovirals
For clinicians managing patient treatment with antiretroviral drugs, the interaction of these agents with other medications can pose challenges. Another symposium presenter, Adriana Andrade, MD, MPH, assistant professor at Johns Hopkins University in Baltimore, offered several management strategies, such as taking a full medication history, including leftover medications a patient may still have in the medicine cabinet. “The only way to stay ahead in the drug interaction game is to know what your patients are taking,” Dr. Andrade said.
Some interactions are predictable and hard to miss—the interaction between protease inhibitors and statins, for example—but others can be more unexpected, Dr. Andrade noted, such as interactions between atazanavir/ritonavir and tenofovir. While it’s impossible to memorize every possible drug interaction, it can be helpful to remember metabolic inducers or inhibitors, simplify by remembering broad drug classes, and look up specific interactions if you are planning to use an inducer or inhibitor.
It’s also important to keep an eye on the literature each month for new information about possible interactions, Dr. Andrade said. A stepwise approach can also involve a thorough patient medication history, the use of pocket reference guides, and consulting drug information resources online, such as the AIDSinfo website at the U.S. Department of Health and Human Services. IDSA also offers a service that forwards ID-related messages from the Food and Drug Administration (FDA) on adverse events and other safety information on FDA-approved drugs and biologics. To subscribe, click here.
Audio and synchronized speaker slides from this session and others at the 2009 IDSA Annual Meeting are available for purchase online.
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