Frecuently Asked Questions

Download as pdf- Updated August 23, 2013

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1. What is PrEP?

Pre-exposure prophylaxis, or PrEP, is a new and highly effective HIV prevention strategy that uses prescription pills, also used for HIV treatment, to prevent HIV infection. PrEP has been proven to reduce the risk of acquiring HIV through sex for gay and bisexual men and for heterosexual women and men, and through injection drug use.

2. What is Truvada®?

Truvada is a once-daily pill that contains two medicines -- emtricitabine and tenofovir disoproxil fumarate (FTC/TDF). These drugs are used for HIV treatment and now, through PrEP, are also used for HIV prevention. Truvada is currently the most prescribed HIV treatment drug in the United States, and has been taken by millions of people worldwide. Truvada was approved to treat HIV infection by the U.S. Food and Drug Administration (FDA) in 2004 and was approved for use as PrEP in 2012.

3. How does PrEP work?

When Truvada PrEP is taken consistently, the presence of the drug in the body helps to prevent HIV infection if an individual is exposed to the virus.

4. Who does PrEP work for?

The iPrEx study demonstrated that PrEP works for gay and bisexual men. Two other studies, called Partners PrEP and TDF2, demonstrated that PrEP also protected heterosexual women and men from HIV. The Tenofovir Bangkok study demonstrated that PrEP reduces HIV infections among people who inject drugs.

5. How effective is PrEP? Does it have to be taken every day to work?

When taken consistently, PrEP is highly effective. In an analysis of data from the iPrEx study of gay and bisexual men and trans women, daily PrEP use provided 96-99% protection. PrEP is still very effective even if a daily dose is missed; among participants in the iPrEx study whose blood levels indicated that they had taken PrEP approximately 4 times a week, PrEP provided 90-99% protection against infection. As few as two pills per week provided some protection (76%) in the iPrEx analysis, but the current data are unclear about how non-daily use of PrEP could be timed to maximize protection. To achieve the most protection against HIV, PrEP should be taken every day or as close to every day as possible.

6. Is PrEP different than PEP?

Yes. Post-exposure prophylaxis, or PEP, is when an individual receives HIV treatment immediately after possible exposure to HIV to reduce the chances of infection taking hold. PEP is typically taken for 28 days after a possible exposure. In Pre-exposure prophylaxis, or PrEP, a person who is not infected takes HIV medication in order to reduce their chances of infection if exposed to HIV.

7. Why are there so many different numbers around about how well PrEP works? What’s the real story?

There have been several clinical trials of PrEP. All point to the same result: when used consistently, PrEP is highly effective at preventing HIV transmission through sex or injection drug use.

In the clinical trials of PrEP that have been done so far, half of the participants received the PrEP drug and half received placebo (sugar) pills. The two groups were then compared to see how well PrEP worked to prevent HIV.

Each study can produce different numbers because there are different ways to measure how well PrEP worked. One measure of how well PrEP worked is called an “intention to treat” or “ITT” analysis. This measure includes everyone who received PrEP in the study, whether they took the drug or not. Since the ITT analysis includes many participants who received PrEP but chose not to take it, it produces a lower estimate of PrEP’s effectiveness than when we look only at people who actually took the drug.

An “as-treated” analysis, on the other hand, only includes participants who took PrEP consistently, and therefore provides a clearer picture of how effective PrEP is when it is actually used. In the studies that have been completed so far, including Partners PrEP, TDF2, and the Tenofovir Bangkok study, the as-treated analyses showed that PrEP provided 70% - 90% protection against infection in people who used PrEP consistently.

8. Did PrEP “fail” in some studies?

Women in two PrEP clinical trials in Africa, called VOICE and FEM-PrEP, were not protected from HIV by PrEP because so few women in the studies took the medication. Researchers are working to understand why the participants in these two studies did not use the study medication more consistently, and therefore did not attain protective levels of PrEP.

9. Is PrEP a new idea?

While PrEP for HIV is new, taking a medication to prevent an illness (called “prophylaxis”) is a longstanding concept in medicine. For example, drugs are taken to prevent diseases such as malaria, and to prevent HIV infection in infants during childbirth.

10. Is PrEP safe?

Yes. PrEP clinical trials have shown that Truvada PrEP is safe, and the FDA has approved Truvada PrEP as both safe and effective for HIV prevention.

All of the clinical trials studying PrEP performed extensive safety testing. These tests looked at the potential effects of PrEP on participants’ weight, bones and organs, with a particular focus on any potential impact of PrEP on the kidney and liver, since these organs help process the drug in the body. The only differences between people who received PrEP and those who received a placebo (sugar pill) in the studies were small reductions in kidney function or bone density among those using PrEP. In most cases these changes had no impact on participants’ health, and the measures returned to normal on their own, or when PrEP was stopped.

11. Does PrEP cause side effects?

As with all prescription medications, some people taking Truvada PrEP may experience side effects. Side effects with Truvada PrEP have been rare and generally mild and short-term. Nine out of ten people who took Truvada PrEP in the iPrEx study experienced no side effects at all. About one in ten people experienced mild side effects such as nausea, headache and/or weight loss. For most people, those side effects went away on their own after a short time, or when the medication was stopped.

12. Does PrEP cause HIV drug resistance?

PrEP is intended for HIV-negative people. If an HIV-positive person takes Truvada PrEP, the virus in their body could develop resistance to the drugs in Truvada. Anyone who is thinking of using PrEP should confirm that they are HIVnegative with an HIV test immediately before starting PrEP, and should get tested regularly while using PrEP.

13. Does PrEP cause people who use it to have unsafe/unprotected sex?

People who use PrEP regularly are practicing safer sex by taking PrEP. When used daily, PrEP reduces HIV risk by 96- 99%, a much greater reduction in risk than condoms or other forms of safer sex. There has been no evidence from any PrEP trial thus far that PrEP causes people to have more sex without condoms. In fact, condom use increased among participants in several PrEP studies, including iPrEx.

14. Is PrEP available?

The US FDA approved Truvada PrEP for HIV prevention in 2012 and it is available by prescription throughout the country. Like many HIV drugs, Truvada is expensive. However, in the United States…

• Many insurance plans pay for PrEP.
• Free PrEP may be available through demonstration projects that are studying how to make PrEP more useful and accessible.
• The San Francisco citywide heath program for uninsured residents (Healthy San Francisco) provides PrEP to people who cannot afford it.
• A program sponsored by the company that makes Truvada, Gilead Sciences, pays for PrEP for uninsured or underinsured people. Individuals considering PrEP can work with their healthcare provider to apply.

15. Can any healthcare provider prescribe PrEP?

Any healthcare provider who is licensed to write prescriptions can prescribe PrEP. PrEP is new and not all healthcare providers are trained to offer PrEP to patients, however. Talk with your healthcare provider to see if he/she has the experience to discuss whether PrEP is right for you.

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16. Can a person stop and start PrEP?

Yes. Individuals can take PrEP during periods in which they may be exposed to HIV and can stop using PrEP when they are in a period where they are less likely to be exposed to HIV. However, research indicates that a person must take PrEP for about a week (seven consecutive days) to achieve the concentrations of the PrEP drug needed to protect against HIV infection. PrEP should also be continued for 28 days after the last possible exposure to HIV. Other PrEP dosing schedules (e.g., taking the drug only before a sexual encounter) are being studied, but no evidence is available yet about whether they might be effective.

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17. Does a person have to use a condom while using PrEP?

When taken regularly, PrEP provides a very high level of protection against HIV infection whether you use a condom or not. However, PrEP does not protect against syphilis, gonorrhea, Chlamydia, hepatitis B, hepatitis C, herpes or genital warts; and does not prevent pregnancy. Using a condom adds protection against these other diseases and pregnancy.

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18. Why make PrEP available when condoms are also highly effective against HIV through sexual exposure?

Condoms have been and remain an important tool to reduce HIV risk. But condoms are not enough to stop HIV. PrEP is an additional tool that can help achieve an AIDS-free future.

A number of studies indicate that condom use is low among sexually active people. And a new research analysis from the US Centers for Disease Control and Prevention (CDC) indicates that inconsistent use of condoms, which is very common, is no more effective at preventing HIV among sexually active gay and bisexual men than not using condoms at all.

Ensuring broad access to PrEP for everyone at risk for HIV infection is consistent with efforts to make condoms widely available for people who are at risk for HIV through sexual transmission. Our common goal should be to ensure that all people have access to every effective way to stay HIV free. For people who cannot or choose not to use condoms at any point, consistent use of PrEP is a highly effective HIV prevention strategy.

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19. Why make PrEP available when clean needles are also highly effective against HIV transmission through injection drug use?

PrEP is not a substitute for clean needles, which are an extremely effective HIV prevention tool for people who inject drugs. Access to clean needles and other harm reductions tool is essential to stopping the HIV epidemic among people who inject drugs. People who inject drugs should have access to clean needles and other harm reduction tools and services, including PrEP.

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20. Why are new HIV prevention methods needed?

According to UNAIDS, about 2.5 million people became infected with HIV in 2011-- nearly 7,000 new infections every day. The need for effective new prevention methods is critical.

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21. What is iPrEx OLE?

iPrEx OLE (OLE stands for Open Label Extension) is a continuation of the iPrEx study designed to provide additional information about the long term safety of Truvada PrEP and the behavior of people taking PrEP over a longer term. iPrEx OLE takes place at sites in Peru, Ecuador, Brazil, the United States, South Africa and Thailand.

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22. Is this research funded by a drug company?

No. All PrEP clinical studies have been funded by independent agencies, including the National Institutes of Health (NIH), Bill & Melinda Gates Foundation, the CDC, University of Washington, Medical Research Council Clinical Trials Unit in the UK and Agence Nationale de Recherches sur le sida et les Hepatites Virales in France. The company that makes Truvada, Gilead Sciences, has donated drugs for PrEP studies but had no control over their design, implementation or results.

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23. Why was Truvada used in PrEP studies?

PrEP clinical trials have used Truvada or one of its component drugs, tenofovir, because they are taken once daily, remain in the bloodstream for a long time and have relatively low rates of side effects or drug resistance. Pre-clinical studies of these drugs as PrEP were also promising, which is why they were selected for human studies. Other studies are looking at the potential use of other HIV drugs as oral PrEP, but these studies are not yet concluded. Currently, only Truvada is FDA-approved as HIV PrEP.

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24. What are PrEP Demonstration Projects?

PrEP demonstration projects provide PrEP to people at risk for HIV in order to better understand who can most benefit from PrEP and how PrEP can best be delivered in different settings. Currently, there are more than 20 PrEP demonstration project sites in California, New York, Florida, Illinois, Louisiana, Maryland, Michigan, Tennessee, Philadelphia and Washington DC.

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25. What additional PrEP research is underway?

Additional PrEP studies are being conducted in several countries to evaluate different PrEP medications, formulations and regimens. A comprehensive list of studies and demonstration projects is available here.

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