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Basic Questions and Answers About Post-Exposure Prophylaxis (PEP)

March 24, 2015

Basic Questions and Answers about Post-Exposure Prophylaxis or PEP

PEP is the use of antiretroviral drugs after a single high-risk event to stop HIV from making copies of itself and spreading through your body. PEP must be started as soon as possible to be effective -- and always within 3 days of a possible exposure. If you think you may have been exposed to HIV very recently, see a doctor as soon as possible to find out if PEP is right for you.

What Is PEP?

PEP stands for post-exposure prophylaxis. It involves taking antiretroviral medicines as soon as possible, but no more than 72 hours (3 days) after you may have been exposed to HIV, to try to reduce the chance of becoming HIV-positive. These medicines keep HIV from making copies of itself and spreading through your body. Two to three drugs are usually prescribed, and they must be taken for 28 days. PEP is not always effective; it does not guarantee that someone exposed to HIV will not become infected with HIV.

Is PEP Right for Me?

PEP is used for anyone who may have been exposed to HIV very recently during a single event. It is not the right choice for people who may be exposed to HIV frequently. (See "Can I take a round of PEP every time I have unprotected sex?" for more information)

Your health care provider will consider whether PEP is right for you based on the risk of your exposure.

Health care workers are evaluated for PEP if they are exposed to blood or body fluids of a patient who is infected with HIV. The risk of getting HIV infection this way is less than 1 in 100 exposures.

PEP can also be used to treat people who may have been exposed to HIV during a single event unrelated to work (e.g., unprotected sex, needle-sharing injection drug use, or sexual assault).

Keep in mind that PEP should only be used in situations right after a potential HIV exposure. It is not a substitute for regular use of other proven HIV prevention methods, such as correct and consistent condom use or use of sterile injection equipment.

If you are prescribed PEP, you will be asked to return for HIV testing at 4 to 6 weeks, 3 months, and 6 months after the potential exposure to HIV. Because PEP is not always effective, you should keep using condoms with sex partners while taking PEP and should not share injection equipment with others.

When Should I Take PEP?

PEP must begin within 72 hours of exposure, before the virus has time to make too many copies of itself in your body.

Starting PEP as soon as possible after a potential HIV exposure is important: research has shown that PEP has little or no effect in preventing HIV infection if it is started more than 72 hours after HIV exposure. HIV makes copies of itself once it enters your body, and it takes about 3 days for it to spread through your body. When HIV is only in a few cells where it entered your body, it can sometimes be stopped by PEP, but when it is in many cells in many places in your body, PEP will not work.

Two to three drugs are usually prescribed, and they must be taken for 28 days.

Does PEP Have Any Side Effects?

PEP is safe but may cause side effects like nausea in some people. These side effects can be treated and are not life-threatening.

Where Can I Get PEP?

Some of the places you can go to seek treatment include your doctor's office, emergency rooms, urgent care clinics, or a local HIV clinic.

How Can I Pay for PEP?

If you are a health care worker who was exposed to HIV on the job, your workplace health insurance or workers' compensation will usually pay for PEP.

If you are prescribed PEP after sexual assault, you may qualify for partial or total reimbursement for medicines and clinical care costs through the Office for Victims of Crime, funded by the US Department of Justice (see the contact information for each state).

If you are prescribed PEP for another reason, and you cannot get insurance coverage (e.g., Medicaid, Medicare, private, or employer-based), your health care provider can apply for free antiretroviral medicines through the medication assistance programs run by the manufacturers. Online applications can be faxed to the company, or some companies have special phone lines. These can be handled urgently in many cases to avoid delay in getting medicine.

Can I Take a Round of PEP Every Time I Have Unprotected Sex?

PEP should only be used right after an uncommon situation with potential HIV exposure. If you are often exposed to HIV, for example, because you often have sex without a condom with a partner who is HIV-positive, repeated uses of PEP are not the right choice. That's because, when drugs are given only after an exposure, more drugs and higher doses are needed to block infection than when they are started before the exposure and continued for a time thereafter. That's an approach called pre-exposure prophylaxis, or PrEP. PrEP means taking a daily pill (brand name, Truvada) for months or years. This keeps medication in your body to keep HIV from making copies of itself and spreading infection through your body anytime you are exposed. If you are at ongoing risk for HIV, speak to your doctor about PrEP.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.
See Also
More on Treatment After Exposure to HIV


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