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HIV Prevention

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Pre-Exposure Prophylaxis (PrEP)

Last Reviewed: June 9, 2016

Key Points

  • Pre-exposure prophylaxis (PrEP) can help prevent HIV infection in people who don’t have HIV but who are at high risk of becoming infected with HIV.
  • PrEP involves taking a specific HIV medicine every day. PrEP is most effective when taken consistently each day.
  • According to the Centers for Disease Control and Prevention (CDC), by taking PrEP every day, a person can lower their risk of getting HIV from sex by more than 90% and from injection drug use by more than 70%.

What is PrEP?

PrEP stands for “pre-exposure prophylaxis.” The word “prophylaxis” means to prevent or protect from an infection or disease.

PrEP can help prevent HIV infection in people who don’t have HIV but who are at high risk of becoming infected with HIV. PrEP involves taking a specific HIV medicine every day. If a person is exposed to HIV, having the HIV PrEP medicine in the person’s bloodstream can help stop HIV from setting up a permanent infection in the body.

What HIV medicine is used for PrEP?

The HIV medicine currently prescribed for PrEP is a combination pill called Truvada. Truvada is made up of two HIV medicines: tenofovir disoproxil fumarate (brand name: Viread) and emtricitabine (brand name: Emtriva). Truvada was approved by the U.S. Food and Drug Administration (FDA) to treat HIV in 2004, and it was approved by FDA for use as PrEP in July 2012.

Other medicines are being studied for possible use as PrEP. These medicines are called investigational drugs, and none of them have been approved by FDA yet. To find out more about investigational HIV drugs, read the AIDSinfo What is an Investigational HIV Drug? fact sheet.

Who should consider taking PrEP?

PrEP is for people who don’t have HIV but who are at high risk of becoming infected with HIV through sex or injection drug use. 

You may want to consider PrEP if you are HIV negative and

  • you are in an ongoing sexual relationship with an HIV-positive partner; or
  • you are a gay or bisexual man who is not in a monogamous relationship with a recently tested, HIV-negative partner, and you have either 1) had anal sex without a condom in the past 6 months, or 2) been diagnosed with a sexually transmitted disease (STD) in the past 6 months; or
  • you are a heterosexual man or woman who is not in a monogamous relationship with a recently tested, HIV-negative partner, and you do not always use condoms during sex with partners whose HIV status is unknown and who are at high risk of HIV infection (for example, people who inject drugs or have bisexual male partners); or
  • you have injected drugs in the past 6 months, and you have either 1) shared needles or injection equipment in the past 6 months, or 2) been in a drug treatment program in the past 6 months.

The above are some examples of people who may benefit from PrEP. If you think PrEP may be right for you, talk to your health care provider.

Does PrEP work?

PrEP is most effective when taken consistently each day. According to CDC, by using PrEP every day, you can lower your risk of getting HIV from sex by more than 90% and from injection drug use by more than 70%. Adding other strategies, such as condom use, along with PrEP can reduce a person’s risk even further.

Does PrEP cause side effects?

Most people taking PrEP do not have any serious side effects from the medicine. Some people taking PrEP may have nausea, but this usually goes away over time. Talk to your health care provider if you have any side effect that bothers you or that does not go away.

What should I do if I think PrEP could help me?

If you think you may be at high risk for HIV and that you might benefit from PrEP, talk to your health care provider. If you and your health care provider agree that PrEP might reduce your risk of getting HIV, the next step is a physical examination, an HIV test, and other blood tests. If the tests show that PrEP is likely to be safe for you and that you might benefit from PrEP, your health care provider can give you a prescription. 

Many health insurance plans cover the cost of PrEP. For people with limited income and no insurance, a commercial medication assistance program provides free PrEP.

What happens once I start PrEP?

Once you start PrEP, you will need to take PrEP every day. If you don’t take PrEP every day, there may not be enough medicine in your bloodstream to block HIV. Studies have shown that PrEP is much less effective if people do not take it every day.

You should keep using condoms while taking PrEP. When PrEP is taken daily, it offers a lot of protection against HIV infection, but not 100%, so condom use is still important. PrEP also does not reduce the risk of getting any other STDs. Read this fact sheet from CDC for information on how to use condoms correctly.   

If you are having trouble taking PrEP every day or if you want to stop taking PrEP, talk to your health care provider.

How can I learn more about PrEP?

Visit the websites below from CDC to learn more about PrEP. This fact sheet is based on information from these sources: 

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