Post-Exposure Prophylaxis

PEP is a course of anti-HIV medication that needs to be taken daily over the course of a month. The drugs have been available for HIV prevention since the early- to mid-1990s for health workers who have had 'needle-stick' or similar injuries. More recently, PEP has been made available under strict prescribing guidelines to people who might have been exposed to HIV during sex. You have up to 72 hours to take it, but it becomes less effective with each passing hour.

History

AZT was approved as a treatment for AIDS in 1987. As AIDS patients started seeking treatment in medical centers, it sometimes rarely happened that somehow a healthcare worker would be exposed to HIV in the course of their occupation. Since healthcare workers were in a clinical setting anyway, AZT was at hand, and some people thought to try giving them AZT to prevent seroconversion. This practice dramatically decreased the incidence of seroconversion among health workers when done under certain conditions.

Later the question arose of whether to give HIV treatment to people who had non-occupational exposure, for example, when two serodiscordant people have unprotected sex in a single incidence such as when a condom breaks, or in the case of unprotected sex with an anonymous partner, or in the case of a non-habitual incident of sharing a syringe for injection drug use. Evidence suggests that PEP also reduces the risk of HIV infection in these cases.

Treatment

In the case of HIV infection, post-exposure prophylaxis is a course of antiretroviral drugs which reduces the risk of seroconversion after events with high risk of exposure to HIV (e.g., unprotected anal or vaginal sex, needlestick injuries, or sharing needles). The CDC recommends PEP for any HIV negative person who has recently been exposed to HIV for any reason.

To be most effective, treatment should begin within an hour of infection. After 72 hours post-exposure PEP is much less effective, and may not be effective at all. Prophylactic treatment for HIV typically lasts four weeks

While there is compelling data to suggest that PEP after HIV exposure is effective, there have been cases where it has failed. Failure has often been attributed to the delay in receiving treatment, the level of exposure (i.e., the viral load received), or both. However, for non-occupational exposures, the time and level of exposure are based on patient-supplied information; absolute data is therefore unavailable. PEP can also slow down the development of antibodies, potentially causing false negatives on a later HIV test. Doctors will advise patients who received PEP to get a test at 6 months post-exposure as well as the standard 3 month test.

The antiretroviral regimen used in PEP is the same as the standard highly active antiretroviral therapy used to treat AIDS. It requires close compliance and can have unpleasant side effects including malaise, fatigue, diarrhea, headache, nausea and vomiting.

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