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. When starting daily PrEP, it takes about seven days to reach high levels of protection against HIV.
Truvada and Descovy are both two-drug, antiviral combinations containing emtricitabine and tenofovir for the treatment of HIV-1 infection, and for pre-exposure prophylaxis (PrEP) to reduce the risk of HIV-1 infection. The difference between TRUVADA and DESCOVY is in the form of tenofovir contained in each product. DESCOVY contains a newer form of tenofovir called tenofovir alafenamide (TAF) and TRUVADA contains the original form of tenofovir as tenofovir disoproxil fumarate (TDF).
Tenofovir alafenamide is a prodrug of tenofovir that has been designed to enter HIV-infected cells more efficiently than TDF, and it can therefore be given at a much lower dose (less than one-tenth) than TDF. TAF (DESCOVY) appears to be associated with less kidney toxicity and decreases in bone density compared to TDF (TRUVADA)
Both DESCOVY and TRUVADA are EQUALLY effective in preventing HIV.
Before a doctor can prescribe PrEP (brand name: Truvada or Descovy), you need to:
• Find a doctor that is trained to prescribe and maintain the proper protocol for PrEP. Not sure how to find a doctor? Ask a trusted friend that is on PrEP or at a HIV testing program.
• Have an office visit with the doctor where he or she evaluates your risk of HIV exposure based on your sexual activities. Being honest and open with your doctor is very important.
• Be tested for HIV to confirm you’re currently negative for HIV
• Be tested for Hepatitis B
• Be tested for healthy kidney functions
• Confirm that you’re not taking other HIV or Hepatitis B medications
• Understand that while PrEP is generally considered safe for most people, there are known safety risks associated with any medication.
• For women: Undergo a pregnancy test and decide if PrEP is still right for you if you’re pregnant
Once you’re on PrEP, you must:
• Take the medication as prescribed every day (PrEP "on demand" is also an option for some people, please scroll down to the next section for more information)
• Visit your doctor every 2-3 months for lab tests, including an HIV test and kidney function test
• Monitor yourself for side effects of PrEP and contact your doctor with any concerns
• Remain honest and open with your doctor
• Understand that PrEP is only one part of your personal strategy to reduce your risk of HIV
Additionally, when you’re on PrEP, it is highly recommended that you:
• Be tested regularly for gonorrhea, chlamydia, and syphilis
• Strongly consider receiving a Hepatitis B vaccine
• Continue practicing safer sex consistently, however you choose to define that for yourself
On-demand PrEP (also known as PrEP 2-1-1 or event-driven PrEP) is a way of taking TRUVADA or DESCOVY to protect against HIV when you need it, instead of every day. Essentially, you take it before and after sex — it is a bit more complicated than that, so please read below under "What is the dosing schedule?". This method is regularly prescribed in some European countries but is not officially approved in the US, though some US healthcare providers are now recommending it).
On-demand PrEP can be a good option if sex is less frequent and/or more predictable. Some people want to save money by using fewer pills (if they have sex no more than once or twice a week). The research finds intermittent PrEP just as effective even if it is used relatively infrequently.
Others want to reduce the potential for side effects. However, some research suggests that intermittent PrEP users may be more likely to experience gastrointestinal and renal (kidney) side effects than daily PrEP users. Still others believe they are more likely to remember to take intermittent PrEP than a daily pill, but there’s some evidence that daily PrEP use results in better average adherence than on-demand use.
On-demand dosing has been studied and shown to work in cisgender men who have sex with men. It has not been studied in cisgender women, transgender men or women, or injection drug users. For people who have vaginal/front hole sex, daily PrEP with good adherence (6-7 doses per week) is the only regimen proven to work. The most recent research shows that on-demand PrEP is may be significantly less effective in transgender women who take feminizing hormones.
On-demand dosing involves the following steps. For a single sexual episode, it requires a total of 4 Truvada pills.
All the same lab tests are still required before you start to use on-demand PrEP – just as for daily PrEP.
On-demand PrEP has been tested and proven highly effective in a trial called IPERGAY conducted in 2012-14, which enrolled 400 HIV-negative, cisgender men who have sex with men. Among the subjects given Truvada (including those who did not always take it), HIV infections were reduced by 86% compared to those given a placebo. No one who took the pills as directed acquired HIV. Even users who had relatively infrequent sex were protected, according to an analysis in 2017. A follow-up “open-label” study (everyone was given the real medication), with 361 participants, showed a 97 percent reduction of HIV diagnoses including those who did not take the medication.