Antiretroviral medication not only helps people living with HIV. It also plays a role in preventing transmission of the virus.

Pre-exposure prophylaxis (PrEP): PrEP is an HIV prevention tool in which an HIV-negative person takes antiretroviral medication to reduce the risk of contracting HIV. Currently, there are three FDA-approved medications for PrEP: 

  • Truvada (tenofovir disoproxil fumarate/emtricitabine)
  • Descovy* (tenofovir alafenamide/emtricitabine)
  • Apretude (extended-release cabotegravir)

*Descovy has not yet been indicated in individuals at risk of HIV from receptive vaginal sex.

Click here for the POZ HIV PrEP Drug Chart for more info on dosing, side effects, drug interactions for each of the available options.

When antiretroviral medication builds up in the human body, it can stop HIV from replicating and establishing an infection. PrEP was approved in 2012 by the U.S. Food and Drug Administration (FDA) with the requirement that it be used every day, even during periods of minimal or low-risk sexual activity. Studies are exploring intermittent dosing strategies (for example, using PrEP only during high-risk periods) as well as different medications that could be used as PrEP. In 2021, the first long-lasting injectable form of PrEP was approved. 

You may benefit from PrEP if you test negative for HIV and:

  • you have had anal or vaginal sex in the past 6 months, and you:
    • have a sexual partner with HIV (especially if the partner’s viral load is detectable or unknown),
    • have not consistently used a condom, or
    • have been diagnosed with and sexually transmitted infection in the past 6 months.
  • you inject drugs and have an injection partner with HIV or if you share needles, syringes or other injection equipment,
  • you’ve been prescribed PEP (post-exposure prophylaxis) and report continued risk behavior or have used mulitple courses of PEP.

According to CDC recommendations, before prescribing PrEP, health care providers should thoroughly assess a patient’s HIV risk behaviors and also administer an HIV test. (More sensitive HIV tests can detect a more recent, or acute, infection; however, most home tests will not detect HIV during this “window period.”) Tests for STIs are recommended. So, too, are tests for kidney function—tenofovir is associated with kidney toxicity—and hepatitis B virus (HBV), given that Truvada is also active against HBV and must be used cautiously.

It is recommended that providers prescribe no more than a 90-day supply of oral PrEP and to offer extensive HIV risk-reduction counseling, adherence counseling and condoms. It is recommended that, before renewing Truvada or Descovy scripts, providers follow up with patients every two to three months to test again for HIV, to assess adherence and HIV risk behavior, and to provide ongoing support and counseling. Kidney function testing is again recommended three months after a person first starts PrEP and yearly thereafter. Long-acting injectable PrEP needs to be administered by a health care worker every other month. Tests for common STIs are also recommended every six months, even if a person has no symptoms.

PrEP is appropriate for periods of time when people have greater risk for contracting HIV. Those periods may be short, long or recurrent, depending on the individual. The CDC also recommends that before people discontinue PrEP—whether because of safety concerns, a positive HIV test result, or a person requests to stop treatment—their providers should link them to HIV care (if a person has become infected) or ongoing HIV risk-reduction counseling and support. For people who have hep B, their providers should also discuss whether to continue treatment as a means to control their hepatitis.

How does PrEP work?
PrEP only works if you take it. Data from the iPrEx trial show that daily adherence of oral PrEP reduces HIV risk between 96 percent and greater than 99 percent. Those who took four doses a week remained fully protected, and those who took two lowered their chance of getting HIV by 76 percent. Data from the HPTN 083 and HPTN 084 studies showed that long-acting injectable regimens are even more effective than PrEP pills at preventing HIV acquisition.

What about side effects?
Rates of side effects while on oral PrEP are low. Mild symptoms such as stomach cramps, headaches and loss of appetite may appear the first few weeks. Long-term use raises issues of kidney health and bone density. Health care providers should regularly test for kidney function. The most common side effect of long-lasting injectable PrEP is injection site reactions, including pain, redness or swelling. Rare but potentially serious adverse effects of injectable PrEP include hypersensitivity reactions, hepatotoxicity (liver damage) and depression.

What about drug resistance?
If you are HIV positive and start PrEP, the virus can become resistant to one or both meds in Truvada. This mutated virus is weaker and less likely to transmit. Still, it is important you are not in the window period of HIV infection when beginning PrEP.

Do I still need to use condoms?
PrEP is supposed to be used along with safer-sex practices, such as condom use and regular HIV testing.

How can I access PrEP?
At over $1,500 a month, oral PrEP is not cheap. Most insurance plans cover it, but you may have to work with your health care team before you get a prescription and coverage. Injectable PrEP is expected to cost about as much as two months’ worth of oral PrEP.

The Gilead Advancing Access program is available for qualified individuals in the United States who cannot afford Truvada or Descovy for PrEP. The program includes a co-pay assistance program for commercially insured individuals and a medication assistance program (MAP), which provides free medication for those who qualify based on financial need. For more info, visit 

Click here for more info about ViiVConnect, a variety of programs designed to help eligible patients save on prescribed ViiV Healthcare medications.  

Last Reviewed: January 5, 2023