This patient is at risk for HIV infection because of regular sexual activity with an infected person and should be considered for preexposure prophylaxis (PrEP). Daily combination tenofovir-emtricitabine therapy is FDA approved for prevention of HIV infection in persons considered at ongoing risk for infection. Studies have shown efficacy in men who have sex with men, heterosexual couples, and injection drug users. Rates of effectiveness in prevention depend on adherence to the medication, and prophylaxis should always be accompanied by safer-sex counseling. Testing for HIV and other sexually transmitted diseases, pregnancy, and kidney function should be performed before initiation of prophylaxis and every 2 to 3 months during preventive therapy.

Reduction in viral load with antiretroviral therapy does reduce transmission of HIV, although transmission may still occur even with undetectable blood levels. Although consistent condom use can reduce the risk for HIV transmission, the addition of PrEP can further reduce rates of acquisition of HIV and should be considered in those at high risk. Such preventive therapy should be taken daily, however, and not episodically only with exposure.

Studies on which FDA approval was based used a two-drug combination of tenofovir-emtricitabine alone without additional medication. Therefore, no clear indication exists for exposing the patient to the additional cost and risk of a third drug. The three-drug regimen of combination tenofovir-emtricitabine and raltegravir is the preferred regimen for postexposure prophylaxis. Whereas tenofovir alone has shown some benefit in reducing acquisition of HIV because of concerns about resistance, combination tenofovir-emtricitabine is preferred for PrEP.