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KEY POINTS
■ Observational data demonstrate that postexposure prophylaxis is about 81% effective in preventing seroconversion to acute HIV infection.
■ Most guidelines say PEP should be initiated within 72 hours after the exposure and continued for 28 days or roughly 4 weeks. Others insist that PEP should be initiated within 36 hours of exposure for optimal prevention.
■ Two-drug and three-drug regimens are available. Compared to three-drug regimens, two-drug regimens offer lower cost, fewer side effects, and improved adherence but are often not the optimal choice.
■ The regimen should be chosen based on factors such as the prevalence of antiretroviral drug resistance in the community, whether the source patient's HIV status is known, and the source patient's treatment history. Close follow-up and periodic antibody testing are essential.
In the early 1990s, postexposure prophylaxis (PEP) was used solely in health care workers who had been occupationally exposed to the human immunodeficiency virus. Since then, however, providing antiretroviral (ARV) therapy as a prophylactic measure to those exposed to HIV through sexual contact or IV drug use has become widely accepted. Since seroconversion does not occur instantaneously, a short window may be present after HIV exposure where proper prophylactic measures may avert fusion of the virus into the cell.1 Observational data demonstrate that postexposure prophylaxis is about 81% effective in preventing seroconversion to acute HIV infection.2 But when is prophylactic therapy appropriate? How is PEP executed, and what follow-up is needed? The answers to these and related questions can be confusing. This article discusses which types of exposures should result in prophylactic therapy, optimal antiretroviral medications for treatment, duration of prophylactic treatment, and follow-up management.
WHEN TO CONSIDER ANTIRETROVIRAL PROPHYLAXIS
Both occupational and nonoccupational exposures have the potential to transmit HIV and may require prophylactic treatment. Occupational exposures are overt, most commonly involving percutaneous needlesticks in the health care setting. Less commonly, occupational exposure can occur through exposure to infected body fluid such as semen, vaginal secretions, breast milk, CSF, and pleural, peritoneal, pericardial, synovial, or amniotic fluids.3 Higher rates of viral transmission to the exposed person are associated with advanced HIV disease (high viral load and low CD4+ T-cell count) in the source patient, deeper puncture wounds, obvious blood on the needle/instrument, and use of the needle in the source patient's blood vessel.1 The amount of visible blood and depth of puncture are directly proportional to the risk of infection. Thus, an exposure involving a shallow puncture wound or without obvious blood on the instrument suggests a lower risk.
Nonoccupational exposures can occur from unprotected sexual contact or sharing needles with an HIV-infected person. Being the receptive partner during anal or vaginal intercourse poses a much higher risk of infection than being the insertive partner. Repeated exposure to shared needles is also riskier than an isolated exposure (Table 1).
Exposed persons who know definitively that they were HIV-negative prior to exposure—that is, they received serologic confirmation of negative status within the past 6 months—require HIV prophylaxis. Exposed persons who believe they are HIV-negative but are not certain—that is, they have had no recent serologic test for HIV or have never been tested—should have a rapid ELISA (enzyme-linked immunosorbent assay) performed before starting postexposure prophylaxis. If a rapid antibody test is not available, PEP should be initiated immediately pending results. If the exposed person is already seropositive, prophylactic treatment is not warranted.
In occupational settings, the source patient is often available for immediate testing via rapid ELISA to determine HIV status. If the ELISA result is negative, PEP is generally not recommended.3 However, if the source patient engages in high-risk behavior and may have HIV infection but not yet be antibody positive, the exposed person should begin PEP. If rapid HIV testing is not immediately available, PEP should always be initiated, regardless of the status of the source patient, while test results are pending.1 If a negative result is returned, PEP may then be discontinued.