HIV post-exposure prophylaxis (PEP)

Who should consider PEP

Here are the two most important criteria for PEP treatment:

• Treatment should be started within 72 hours of exposure
• The exposure should be high risk

Let’s talk about each of these in more detail.

PEP timing

• Treatment should be started within 72 hours of exposure
• Ideally, it should be given within the first 24 hours after exposure
• Once the decision is made, the first dose should be taken

High-risk exposure, defined

Any (both insertive and receptive) unprotected vaginal or rectal sex or exposure to blood or bodily fluids mixed with blood is considered high risk.

The table below shows the chance of contracting HIV through various types of unprotected sexual activities.

*The number of people who engage in the activity, unprotected, who contract HIV.

How doctors decide whether to recommend PEP

Not every unprotected sexual encounter is treated the same way by doctors—some are considered riskier than others. People who had high-risk contact are encouraged by doctors to initiate PEP. The following are considered high risk:

• Unprotected sex with an HIV-positive partner
• Sexual assault

If you’re not in either of those categories, you can decide whether to be on PEP by looking at your statistical chance of getting HIV (based on the type of sexual activity you had) and your personal wishes.

If you’re already on PrEP

Typically, someone who is taking PrEP medications and not missing doses frequently does not need to also take PEP after a high-risk exposure. But if PrEP is taken sporadically or if it wasn’t taken within the last week before exposure, PEP is advised.

The common PEP regimen

PEP is a 28-day, three-drug regimen. Most commonly used is the combination of Truvada plus raltegravir or dolutegravir.

• Truvada: 200/300 mg once a day

PLUS

• Raltegravir 400 mg twice daily

OR

• Dolutegravir 50 mg once daily

This is a 28-day regimen.

Dolutegravir vs. raltegravir

Dolutegravir is preferred for two reason:

• It’s convenient—it only has to be taken once a day
• It’s a better medication for a drug-resistant HIV virus

PEP effectiveness

No clinical trials on non-occupational post-exposure prophylaxis have been conducted. PEP is not 100% effective, but it is very effective if taken consistently and correctly. It is believed that it is more than 80% effective.

Reasons for PEP failures

Here are the most common reasons for a PEP regimen failure:

• Not taking the medication as prescribed (missing doses)
• Delay in starting the medication (ideally it should be initiated within the first 24 hours, but it can be started within 72 hours of exposure)
• Ongoing HIV exposure
• Drug-resistant HIV virus (very uncommon)

Testing necessary before, during, and after PEP

Here we summarize the testing necessary before starting PEP, post-treatment testing, and testing needed during PEP.

Please keep in mind that PEP treatment should not be delayed—the first dose should be administered as soon as possible.

Monitoring during PEP

A person who is receiving HIV PEP should have the following tests after the first dose (within the first few days):

• One-time rapid HIV antigen/antibody test
• Hepatitis B (Hep B antigen test)
• Hepatitis C (Hep C antibody test)

Post-treatment testing

After PEP has been completed, a one-time fourth-generation HIV test is necessary.

Why routine multiple HIV tests are unnecessary during PEP

Most people are very concerned getting HIV and want frequent HIV testing while they’re on PEP. But it’s unnecessary—here’s why:

• The test usually remains negative because HIV has a “window” during which infection is not detected
• The HIV virus may be falsely suppressed while someone is on medication
• People may (unwisely) stop taking the medication because they assume they’re negative after a few negative tests within during the 28 days they’re on PEP

The above information applies to all types of HIV testing: the fourth-generation antigen/antibody test, HIV RNA test, or antibody test.

Why Descovy is not used instead of Truvada in PEP

Descovy presently is not used in PEP because data are insufficient to support its efficacy.

When PEP can be stopped

PEP can be stopped at any time without tapering the medication dose.

There are a few reasons people stop the medication:

• Their partner agrees to be tested and tests negative for HIV
  • A negative rapid HIV test (fourth-generation antigen/antibody) is usually enough
  • A negative HIV RNA is necessary if new infection suspected
• Their HIV-positive partner has an HIV RNA test showing suppressed virus (undetectable viral load)

Most common PEP side effects

The most PEP side effects are mild and do not result in discontinuation of the regimen. This table shows the most common side effects and the percentage of people who experience them:

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