How does PrEP work?
Researchers have developed many potent drugs that stop HIV’s life cycle inside human immune cells. Like other HIV medicines, PrEP drugs work by already hanging out in those cells before an exposure to the virus—either through sex or by sharing needles.
Taking PrEP as prescribed means the drugs will stay at protective levels inside your immune system. If you have an exposure to HIV, the virus can’t reproduce or spread throughout the body, and it will eventually die.
PrEP medications
Three medications are approved as PrEP in the U.S. by the Food & Drug Administration (FDA): Truvada, Descovy, and Apretude, which is long-acting injectable cabotegravir. There are also generic versions of Truvada that are available for PrEP. Both Truvada and Descovy are also used for treating HIV infection, so there’s a lot of real-world experience with using them. Cabotegravir is also used for HIV treatment.
Truvada and Descovy combine two drugs into one pill: emtricitabine and tenofovir. Truvada contains emtricitabine (FTC) 200 mg and tenofovir DF (TDF) 300 mg. Descovy contains emtricitabine (FTC) 200 mg and tenofovir AF (TAF) 25 mg.
Injectable cabotegravir (600 mg) is delivered as a single 3-ml injection into the ventrogluteal muscle, which is a muscle on the side of your butt.
Discussing these medicines with your health care provider can help you choose which is best for you. If you find one isn’t right for you, it may be possible to switch.
| Truvada |
Descovy |
| >99% effective |
>99% effective |
| Daily use & PrEP 2-1-1 |
Daily use (Although Descovy for PrEP 2-1-1 is being studied, there is inadequate clinical data to support this regimen now) |
Everyone, including:
- Gay & bisexual cis men
- Trans women
- Trans men
- Heterosexuals
- Cis women
- People who inject drugs
|
Only:
- Gay & bisexual cis men
- Trans women
(No clinical data to support use in people who may be exposed to HIV through injection drug use or vaginal sex) |
| Both medicines have very low rates of side effects overall. Some people experience “start-up” symptoms including diarrhea, nausea and vomiting, which usually resolve in the first three months of PrEP use. |
Both medicines have very low rates of side effects overall. Some people experience “start-up” symptoms including diarrhea, nausea and vomiting, which usually resolve in the first three months of PrEP use. |
| People with osteoporosis should avoid |
Safer to take for people with osteoporosis |
| People with kidney issues or a strong family history of kidney disease should avoid |
Safer to take for people with kidney issues or a strong family history of kidney disease, though monitoring still recommended |
| May cause a small degree of weight loss1 |
May cause a small degree of weight gain2 |
| May cause small decreases in HDL, LDL and total cholesterol1 |
May cause small increases in LDL cholesterol and triglycerides2,3 |
| Same cost ($1,845/month without insurance)Generic version may be available in 2020 |
Same cost ($1,845/month without insurance) |
| Covered by insurance |
Likely covered by insurance |
| Covered by assistance programs for medication and medical care costs |
Covered by assistance programs for medication and medical care costs |
| Larger pill than Descovy |
Smaller pill than Truvada |
What is PrEP care?
PrEP is available by prescription only, not over the counter, and involves regular tests and care. In a nutshell, getting and staying on PrEP includes the following:
Talking to your healthcare provider
If your healthcare provider can prescribe PrEP, great! If they need guidance, they can read the federal guidelines or call the national PrEPline. If they decline to prescribe PrEP, contact a telehealth service or search for a PrEP provider through PleasePrEPMe. Remember, you deserve a healthcare provider who supports you and your sexual health.
Getting your tests done
At your PrEP visits, you will have routine tests for HIV, STIs, and kidney health, and get your prescription.
Covering costs
Most people can cover costs through their health plans. If you’re uninsured or your out-of-pocket costs are high, assistance programs can help.
Keeping up with PrEP care
See your healthcare provider every three months, get routine tests done, and get your PrEP prescription refilled on time. If you decide to stop taking PrEP, talk to your provider about how to do it safely.
How long until I’m protected?
You need to take a certain number of PrEP doses to reach protective levels in the body. These “lead-in” doses differ depending on the kind of sex you have.
Daily PrEP
For anal sex, seven lead-in doses are recommended. For those at risk for HIV due to anal sex, an alternative option is taking two tablets at once, which provides a high level of protection starting two hours after dosing.
For vaginal or front hole sex, 20 lead-in doses are recommended.
For blood exposures (such as sharing needles), 20 lead-in doses are recommended.
PrEP 2-1-1
The lead-in or “loading” dose is a double-dose (two pills) taken two to 24 hours before you have sex. The closer the lead-in dose is to the 24-hour mark, the higher the level of protection will be.
Long-acting injectable PrEP
At this time, there isn’t data available that tells us how long it takes for injectable cabotegravir to be protective. There is no recommendation to wait for a period of time before having sex once you start injectable PrEP.
How effective is PrEP?
PrEP is very effective when it’s taken consistently and as prescribed. PrEP decreases the risk of HIV infection by about 99% for sex and at least 74% for sharing injection drug equipment. Using additional prevention methods, like condoms or U=U, can reduce this risk even more.
Hundreds of PrEP studies have been done worldwide in various communities. These have included people who have vaginal, front hole, or anal sex, transgender women, and people who inject drugs. In very rare cases, HIV infections have occurred when a person has taken PrEP as prescribed.
Although we know a lot about how well PrEP works, more research is being done to address some gaps in knowledge.
Any side effects with PrEP?
Most people who take PrEP don’t feel side effects. If they do occur, they’re usually mild and resolve within the first one to three months. The most common short-term symptoms for Truvada and Descovy include diarrhea, nausea, vomiting, and loss of appetite. Long-term side effects may also occur, and differ slightly for Truvada and Descovy.
Side effects are similar whether you take daily PrEP or PrEP 2-1-1. Mild side effects can be treated with over-the-counter medicines. If you have a side effect that bothers you or doesn’t go away, or if you have a serious reaction (like a severe rash), immediately ask your healthcare provider about next steps.
Daily oral PrEP does not change the way gender-affirming hormones work, and hormones have not been found to reduce the effectiveness of daily oral PrEP. Transgender men who have vaginal or front hole sex should not use PrEP 2-1-1 because it hasn’t yet been studied this way.
One “side effect” that’s not often mentioned is some people end up feeling less anxious about HIV. You may find that PrEP gives you the mental and emotional space to become more proactive around your sexual health.
Truvada side effects
Possible long-term side effects of Truvada mostly relate to kidney health and slight weight loss. If your kidney lab levels decline, you may be able to stop Truvada and restart it without further problems, or you may be able to switch to Descovy. Kidney health side effects are rare.
Truvada can also slightly reduce bone strength. This is not associated with fractures or broken bones, but it may be a concern for people with osteoporosis or history of non-traumatic fractures. Bone density loss is not ongoing, so there is no continued reduction in bone density for people taking Truvada long-term.
Descovy side effects
Possible long-term side effects of Descovy may include weight gain and increases in cholesterol.
Long-acting cabotegravir
In studies, the most common side effects with long-acting cabotegravir injections are pain, redness, and swelling at the site of the injection.
PrEP Facts content written by Alan McCord and Reilly O’Neal. Medical review by Janessa Broussard, RN, MSN, AGNP-C, vice president of medical affairs at San Francisco AIDS Foundation.
