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Post-exposure prophylaxis (PEP) is any prophylactic treatment started immediately after exposure to a pathogen (such as a disease-causing virus), in order to prevent infection by the pathogen and the development of disease.

[edit] Rabies

PEP is commonly and very effectively used to prevent the outbreak of rabies after a bite by a rabid animal.

The treatment consists of repeated injections of rabies vaccine and immunoglobulin.^[1]

[edit] HIV

In the case of HIV infection, post-exposure prophylaxis is a course of antiretroviral drugs which is thought to reduce 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).

To be most effective, treatment should begin within an hour^[2] of possible infection, and no longer than 72 hours post-exposure. ^[3] Prophylactic treatment for HIV typically lasts four weeks.^[4]

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.^{[citation needed]} In certain cases PEP has been known to slow the development of antibodies by beyond 12 months.^{[citation needed]}

The antiretroviral regimen used in PEP (see highly active antiretroviral therapy) requires close compliance and can have unpleasant side effects including malaise, fatigue, diarrhea, headache, nausea and vomiting.^[4]

[edit] Herpes

Several studies in humans and mice provide evidence that treatment with the antiviral drug Famciclovir soon after the first infection with herpes can significantly lower the chance of future symptomatic outbreaks of herpes. Use of Famciclovir in this manner has been shown to reduce the amount of latent herpes virus in the neural ganglia.^[5][6][7] A review of human subjects treated for five days with Famciclovir 250 mg three times daily during their first herpes episode found that only 4.2 percent experienced a recurrence within six months after the first outbreak, a five-fold decrease compared to the 19 percent recurrence in acyclovir-treated patients.^[8]

Despite these promising results, early Famciclovir treatment for herpes in this or similar dosage regimes has yet to find mainstream adoption. As a result, some doctors and patients have opted for off-label use. One suggested regime is Famciclovir at 10–20 mg/kg per day for 5–14 days, with treatment to commence as soon as possible after the first herpes infection(not the first symptoms or outbreak), and the most effective time for initiating treatment to be five days or less after the initial herpes infection.^[9]

[edit] See also

• Pre-exposure prophylaxis (PrEP)

[edit] References

Wikiversity has learning materials about The allegory of the lookout and post-exposure immunization

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