Pre-exposure Prophylaxis, also known as PrEP, is when people take medicine to lower their risk of getting HIV. HIV works by hijacking healthy immune system cells and using them to produce more of the virus. PrEP prevents the virus from taking hold and starting that process. Currently, a combination of two HIV drugs, tenofovir and emtricitabine, are used for PrEP. This combination is sold under the name Truvada.
PrEP is prescribed for HIV-negative people who are at a higher risk for getting HIV, most commonly through sex or injection drug use. For example, if your partner is HIV positive, you could take PrEP to lower the probability that you will get HIV. PrEP is proven to be very effective when taken correctly, and can lower your risk of getting HIV through sex by 90%, and by injection drug use by 70%.
It is important to remember that PrEP is not a vaccine. Vaccines teach your body to fight infections and last for several years. PrEP works by maintaining certain levels of tenofovir and emtricitabine in your body so that if HIV is introduced, it cannot take hold. You need to take PrEP daily for it to be most effective. Recent studies have shown that taking PrEP at least four days per week is enough to maintain drug levels that are high enough to prevent HIV. But, most of these study participants were men. There is reason to believe that these findings will not hold true for women. Levels of tenofovir and emtricitabine are more variable in women. They are much lower in vagnial tissues than in men’s anogenital tract. This means that missing days of PrEP may lessen its’ effectiveness at preventing HIV more so in women than in men. Even though studies have shown that taking PrEP medication at least four days per week is still effective in men, physicians still recommend taking it every day to ensure its’ effectiveness. PrEP is just as effective for women as it is for men if taken daily as prescribed.
Researchers are currently working on long-acting PrEP medication. A long-term solution is necessary because taking PrEP every day may be difficult or impossible for some people. Right now three possible solutions for long-term prevention are under investigation. The first in an intravaginal ring. This is a ring that is inserted into the vagina that would release antiretroviral drugs slowly over time. Second is an injected form of PrEP. The National Institute of Health (NIH) is sponsoring two studies on the drug cabotegravir, one on cis men and trans women and one on cis women, to see if it can protect them as well as daily oral PrEP. Lastly, the NIH is also testing implanted PrEP. This is a device implanted in the body that releases a PrEP medication over time. These long-acting PrEP solutions would give people more options for lowering their risk of getting HIV.
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