Post-Exposure Prophylaxis (PEP)

What is post-exposure prophylaxis (PEP)?

Post-exposure prophylaxis (PEP) is a treatment you take after being exposed to HIV to prevent getting infected. It’s a combination of medications you take for 28 days. You must start it within 72 hours (three days) of being exposed to HIV for it to have the best chance of working.

HIV (human immunodeficiency virus) is a treatable, but incurable lifelong illness. Exposure is a medical emergency. If you think you’ve been exposed to HIV — through sex, sexual assault, shared needles or a work-related needle stick — go to the nearest emergency room or seek emergency medical attention.

PEP is only meant for emergencies. It’s not meant for long-term protection against repeated HIV exposure. If you’re at high risk for HIV exposure, talk to a healthcare provider about pre-exposure prophylaxis (PrEP).

What happens before starting PEP?

Before or while you start treatment, your provider might take samples of your blood, pee (urine) or other body fluids to run tests. They’ll test you for HIV and look for conditions that might change what PEP medications you take or the doses you’re prescribed. They might test you for:

• Hepatitis B.
• Hepatitis C.
• Pregnancy.
• How well your liver and kidneys function.

Will I be tested or treated for any other infections when I’m at my PEP visit?

Yes, because multiple sexually transmitted infections can be transmitted at the same time. Based on the type of exposure you had, your provider may also test and/or treat you for other sexually transmitted infections, like:

• Gonorrhea.
• Chlamydia.
• Trichomoniasis.

How does post-exposure prophylaxis work?

PEP medications are antiretroviral drugs that work by preventing HIV from making more copies of itself. Each medication uses a different method or stops HIV at a different point in its replication process. Combining medications that work in different ways makes the treatment more effective.

If you use antiretroviral medications early enough, they can stop an HIV infection before it has a chance to establish an infection in your body. When this happens, medications can’t fully get rid of it and it becomes a chronic infection.

What medications are used for post-exposure prophylaxis?

Providers prescribe a combination of antiretroviral medications for PEP. These are the same kinds of medications used to treat HIV. They come in a pill that you swallow. You’ll take a combined pill of emtricitabine and tenofovir disoproxil fumarate (FTC/TDF, Truvada®) or a combined pill of emtricitabine and tenofovir alafenamide (FTC/TAF, Descovy®) plus one of the following:

• Raltegravir/RAL (Isentress, Isentress HD).
• Dolutegravir/DTG (Tivicay™, Tivicay PD).
• A combination of darunavir/DRV (Prezista®) and ritonavir/RTV (Norvir®) or cobicistat/COBI.

Depending on the medication, you might take these pills once or twice a day — make sure you understand the correct schedule. Ask your provider to explain it before you start PEP. Your provider may adjust the dose or types of medications depending on other health conditions you have.

How long after HIV exposure can you take post-exposure prophylaxis?

You need to start post-exposure prophylaxis for HIV no later than 72 hours (three days) after:

• Unprotected vaginal or anal sex (including forcible sex or assault) with someone who has or might have HIV.
• Sharing a needle (for instance, while injecting nonmedical drugs) with someone who has or might have HIV.
• Being exposed at work (for instance, if you were stuck by a needle contaminated with HIV).

How long will I need to take post-exposure prophylaxis?

You need to take PEP medications every day for the full 28 days for them to be effective. If you stop taking them too soon or skip doses, it increases your chances of getting an HIV infection.

Who shouldn’t take PEP?

PEP isn’t recommended if:

• It’s been longer than 72 hours (three days) since your exposure. PEP isn’t likely to work if you start it too late.
• You take PrEP. You don’t need to take PEP if you’ve already been taking pre-exposure prophylaxis consistently.
• You’re not likely to be infected. Oral sex and exposure to body fluids like spit, sweat and tears are unlikely to transmit HIV.

What happens after PEP treatment?

After PEP treatment, you should get repeat HIV testing at four to six weeks, 12 weeks and 24 weeks after exposure. If your exposure is from sexual contact, you may also have repeat screening for other sexually transmitted diseases at four to six weeks after exposure. Please follow up with your primary care provider for this testing.

How well does post-exposure prophylaxis work?

Studies suggest that PEP reduces your risk of getting HIV by over 80%. It might not work as well if you:

• Start PEP too late (more than 72 hours after exposure).
• Are exposed to a type of HIV that’s resistant to PEP medications.
• Are exposed again while taking PEP treatment.
• Miss doses of PEP medications.
• Don’t finish the full 28-day course of treatment.

What are the risks of PEP?

One risk of PEP is that you’ll miss doses or not be able to take the medication as directed. This means the treatment might not be as effective at preventing an HIV infection. PEP can also cause side effects in some people, though they’re usually mild. They include:

• Fatigue.
• Nausea.
• Vomiting.
• Diarrhea.
• Headaches.

These side effects can be managed with over-the-counter medications in most cases. Ask your healthcare provider what over-the-counter medications are safe for you if you experience a side effect.

Where do I go if I’ve been exposed to HIV and need PEP?

HIV exposure is a medical emergency. If you think you’ve been exposed, get emergency medical attention. You can go to:

• An emergency room (ER), accidents and emergency (A&E) or other emergency medical center that can give you immediate attention.
• A sexual health clinic.
• Some primary care providers or family doctors will prescribe PEP. But they might refer you to another provider or the ER, depending on how much experience they have with it.
• If you’re seeking care for a sexual assault, you may see a sexual assault nurse examiner who can provide evidence collection, counseling and follow-up. Most emergency departments offer these services.

Wherever you seek care, if they require an appointment, tell them why you need to be seen and that it’s important to get in immediately. If they can’t see you right away, they should be able to tell you where to go for immediate care.

What questions should I ask my doctor?

It’s very important to take PEP medications exactly as directed. Questions you can ask your provider to make sure you take them correctly include:

• When should I start taking these medications?
• How do I take these medications?
• How many medications do I take each day?
• How many times a day do I take each of these medications?
• What do I do if I miss a dose?
• When should I test for HIV?
• When should I follow up with you or another provider?
• Who can I call if I have additional questions?

Is it worth taking PEP after 72 hours?

PEP usually isn’t recommended if it’s been longer than 72 hours since your exposure to HIV. But talk to a healthcare provider right away if you were exposed to HIV — even if you’re past the three-day mark. They can discuss your options with you.

Can I have sex while taking PEP?

If you have vaginal or anal sex while taking PEP, it’s safest to use a condom or other barrier contraception to protect your partner until you know you don’t have HIV.

Is post-exposure prophylaxis used for preventing other diseases?

Most of the time, you hear about post-exposure prophylaxis for HIV. There are also post-exposure treatments for other infectious diseases. Depending on the disease, the treatment usually includes vaccine or antibody (immunoglobulin) shots. Preventive treatments for some bacterial illnesses are antibiotic shots or pills. Post-exposure prophylaxis is also recommended for exposure to:

• Rabies.
• Tetanus.
• Hepatitis A.
• Hepatitis B.
• Lyme disease.
• Anthrax.
• Mpox.