Chemoprophylaxis To Prevent HIV Infection: An Interim Guidance for Clinicians

Published: December 20, 2010

The New England Journal of Medicine published the results of an historic HIV prevention study on November 23, 2010: Preexposure Chemoprophylaxis for HIV Prevention in Men Who Have Sex with Men by Grant et al. The study demonstrated that men who were assigned to take a combination antiretroviral medication orally on a daily basis decreased their HIV risk by almost half compared to those assigned to take a placebo.

As this is the first published study on this novel approach to HIV prevention, called PrEP (pre-exposure prophylaxis), using available oral medication it is likely that clinicians will be approached by patients requesting PrEP for HIV prevention. The Fenway Institute offers this information for clinicians to review the findings of the study and as interim guidance for prescribing and supporting patients seeking PrEP in advance of development of guidelines by any government agencies or professional societies.

Study Highlights:

    * The populations included in this study were HIV uninfected men who have sex with men (MSM) and Transgender women (MTF), at high risk for sexual exposure to HIV.
    * This was a double blind placebo controlled study in which participants were given a daily dose of either 200 mg of emtricitabine and 300mg of tenofovir disoproxil fumarate  (FTC–TDF) as a single fixed dose combination pill, or placebo.
    * Subjects were followed monthly and received HIV testing, risk-reduction counseling, condoms, and management of sexually transmitted infections at  each routine visit.
    * The results demonstrated the efficacy of daily use of medication in combination with monthly prevention counseling as noted above. Those taking FTC-TDF daily had a 44% lower rate of HIV infection than those in the placebo.  When looking at only those with a high adherence level who reported at taking at least 90% of their medication, the protective effect exceeded 70%.  For those in whom medication was detected in their blood, risk of infection decreased by more than 90%.
    * While side effects were minimal, some on the study developed mild renal insufficiency which resolved when the medication was stopped in almost every case. Those in the treatment group also experienced mild nausea more frequently during the first four weeks of the trial.
    * There was a dramatic increase in efficacy when adherence was high, making ongoing discussion of adherence with patients using medication for prevention of great importance
    * Development of resistance among those taking the medication was low and limited to those who were HIV infected at the time the study began. No resistance to one of the active medications, tenofovir, was seen at any point in the trial. Nevertheless, the possibility of resistance to these medications or other related medications has to be considered, particularly if PrEP users are not fully adherent, continue to engage in sexually risky practices, and do not routinely undergo follow-up HIV testing.

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