What is PrEP?
What is Pre-exposure Prophylaxis (PrEP)?
- Pre = before.
- Exposure = coming into contact with HIV
- Prophylaxis = treatment to prevent an infection from happening
Pre-exposure prophylaxis (PrEP) is an HIV prevention strategy where HIV-negative individuals take anti-HIV medications before coming into contact with HIV to reduce their risk of becoming infected. The medications work to prevent HIV from establishing infection inside the body.
PrEP has been shown to reduce risk of HIV infection through sex for gay and bisexual men, transgender women, and heterosexual men and women, as well as among people who inject drugs.
It does not protect against other sexually transmitted infections (STI) or pregnancy. It is not a cure for HIV.
"HIV-negative individuals use anti-HIV medications to reduce their risk of becoming infected"
What is the difference between PrEP and PEP?
Who does PrEP work for?
PrEP has been shown to help reduce HIV infection risk in multiple studies. The iPrEx trial showed that PrEP reduces the risk of HIV infection among gay and bisexual men and transgender women. Two large trials, Partners PrEP and TDF2, showed that PrEP also reduces the risk of HIV infection among heterosexual men and women. The Bangkok Tenofovir Study demonstrated that PrEP works for people who inject drugs.
Medications approved for PrEP
TRUVADA (also called FTC/TDF)
The U.S. Food and Drug Administration (FDA) approved Truvada for PrEP use in 2012. This medication is taken as a once-daily oral pill, which combines two medicines in one: Emtriva (also called emtricitabine or FTC) and Viread (also called tenofovir disoproxil fumarate or TDF). Truvada works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
"Scientists have focused on these drugs because they are taken once a day, are potent, have relatively low rates of side effects"
Medications currently being studied for PrEP
Other anti-HIV drugs are also currently being studied for PrEP, to provide a wider array of options. They have not yet been shown to be effective for PrEP, nor have they been FDA approved. However, trials are currently underway to determine if they are effective and in a few years we will know more. These drugs include:
MARAVIROC (also called Selzentry or MVC):
This medication is taken as a once-daily oral pill and works by blocking entry of HIV into the body’s cells.
RILPIVIRINE (also known as Edurant):
This medication is injected once a month as a long-acting formulation and works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
DAPIVIRINE (also known as TMC120):
This medication is released by a vaginal ring that is worn for four weeks at a time. The medication works by binding to and disabling an enzyme called HIV reverse transcriptase. By disabling this enzyme, it prevents HIV from making more copies of itself in the body.
TENOFOVIR (also known as tenofovir disoproxyl fumarate, TDF, or Viread):
This medication is one part of the already approved combination pill Truvada. By itself, it is currently being studied as part of a microbicide gel to be inserted rectally and/or vaginally. Tenofovir works by blocking an enzyme called HIV reverse transcriptase. By blocking this enzyme, it prevents HIV from making more copies of itself in the body.
Truvada for PrEP provides 92%-99% reduction in HIV risk for HIV-negative individuals who take the pills every day as directed. If a daily dose is missed, the level of HIV protection may decrease. It only works if you take it. People who use PrEP correctly and consistently have higher levels of protection against HIV.
According to data analysis from the iPrEx study that found PrEP to be effective:
- For people who take 7 PrEP pills per week, their estimated level of protection is 99%.
- For people who take 4 PrEP pills per week, their estimated level of protection is 96%.
- For people who take 2 PrEP pills per week, their estimated level of protection is 76%.
There are not enough data available to provide specific timing guidance on non-daily use, so the FDA recommends PrEP be used daily to achieve the highest level of protection.
A few things to note:
- When starting PrEP, it takes at least seven days to reach high levels of protection against HIV.
- When stopping PrEP, individuals should continue using PrEP for four weeks after the last significant exposure.
- PrEP does not protect against other sexually transmitted infections (STI) or pregnancy. It is not a cure for HIV.
"If you don’t take PrEP consistently it can’t protect you from HIV, but if you do take it regularly it can offer strong protection."
"several studies suggest that PrEP can be effective for both men and women at risk for HIV infection"
Truvada for PrEP is generally safe and well tolerated. Most people on PrEP report experiencing no side effects, but some side effects were reported in clinical trials. Participants in the iPrEx study reported side effects that fall into four main categories (ordered here as most to least common):
Nausea: 9% of those who received Truvada reported nausea in the first month, compared with 5% of those who received placebo. After the first month, there was no difference in reported rates of nausea among those who received Truvada and those who received placebo.
Headaches: 4.5% of participants who received Truvada reported headaches, compared with 3.3% of those who received placebo.
Weight loss: 2.2% of those who received Truvada reported unintentional weight loss of more than 5%, compared with 1.1% of placebo users.
Small increases in serum creatinine: Truvada is known to cause small increases in serum creatinine, a naturally occurring molecule filtered by the kidneys. In this study, 0.3% of those who received Truvada experienced mild increases in serum creatinine that persisted until the next test. Creatinine levels went back down once these participants stopped taking PrEP. Four of the five participants restarted PrEP without recurrence of the creatinine increase. Investigators monitored kidney function throughout the study and found no serious problems.
For most people, these side effects went away on their own after the first few weeks of taking Truvada, or when the medication was stopped.
Truvada for PrEP is taken once a day, at the same time each day. You can take it with or without food. In order to benefit from this medication, adherence is critical. (If you need help keeping up with your medication, check out this handy resource.)
You need to see a doctor for a prescription or join a PrEP research study. If you’re interested in learning more on how to access PrEP, visit this section.
Prices for the medication can be as low as $0 or as high as $2,000 per month depending on whether you have health insurance and/or if you’re enrolled in a research study. If you’re interested in learning more about co-pays and how to potentially get your medication for free or at low cost, visit this section.
It is important to make sure you have not been recently infected with HIV when starting PrEP. Truvada is not designed to be used on its own to treat HIV, so using Truvada PrEP if you already have HIV means you are not getting optimal treatment to suppress the virus; you may be increasing your risk of developing drug resistance and limiting your future options for HIV treatment. If you are recently infected with HIV, there is a “window period” when traditional HIV antibody tests cannot yet detect the virus. When you ask about starting PrEP, your medical provider or study coordinator may suggest an alternative test that can detect HIV infection earlier.