PURPOSE OF REVIEW:
HIV infection among MSM remains a significant issue. Data relevant to MSM populations from animal models, pharmacokinetic studies and clinical trials are summarized and challenges and potential consequences of use of preexposure prophylaxis (PrEP) by MSM are discussed.
Rectal simian-human immunodeficiency virus transmission in macaque models can be prevented by intermittent PrEP dosing. The Preexposure Prophylaxis Initiative (iPrEx) study found that daily oral emtricitabine-tenofovir disoproxyl fumarate (TDF/FTC) decreased HIV infection by 44% among 2499 high-risk MSM. Men with detectable levels of TDF or FTC in plasma and peripheral blood mononuclear cells experienced more than 90% protective effect, emphasizing the importance of adherence. In iPrEX and other studies, PrEP was generally safe and well tolerated. However, it appears that TDF use is associated with a small but significant decrease in mean bone mineral density. No risk compensation has been demonstrated, but this remains an area of potential concern when PrEP is used outside the setting of a placebo-controlled trial. Numerous PrEP trials in MSM are currently underway.
Oral FTC/TDF is effective in preventing HIV infection among MSM. Optimal PrEP agents and dosing regimens now need to be identified. Understanding the patterns of and impediments to PrEP use among MSM is vital and these should be monitored in ongoing demonstration projects and open-label studies.
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