What’s PrEP or Truvada? How Does It Prevent HIV?


What’s PrEP or Truvada? How Does It Prevent HIV?

PrEP stands for Pre-Exposure Prophylaxis. It is an anti-viral pill that an HIV-negative person takes every day to lower their risk of getting HIV(Human Immunodeficiency Virus). The brand name of the pill is Truvada or Descovy but it is also sold under generic names. It is different from post-exposure prophylaxis (PEP).

You can think of it as birth control for HIV. You take a pill once a day, and you’re less likely to get HIV.

How does PrEP prevent HIV?

The drug works by preventing HIV from replicating in the body. It acts as a catalyst that helps the body produce antibodies, which help fight disease-causing germs and viruses. After contact with the virus, the drug blocks the enzyme needed by the virus to replicate. Used correctly, PrEP eliminates the risk of contracting the virus after exposure.

It’s prescribed for people who have a higher risk of getting HIV, including :

  • Men who have sex with men (MSM) and transgender women who:
    • Have had unprotected anal sex in the past six months AND:
      1. Were diagnosed with a sexually transmitted infection (STI) in the past twelve months
      2. Have had unprotected sex with an HIV positive partner where the risk of passing the virus was significant
      3. Have previously used PEP more than once
      4. Consumed psychoactive drugs at the time of sexual encounter(s)
      5. Have had more than two partners in the past 6 months
  • People who inject drugs
  • People who are in a relationship with someone who has HIV, and who have unprotected sex where the risk of passing the virus is significant
  • Sometimes heterosexual people who have unprotected sex with one of these at-risk groups of people. Doctors will decide on a case-by-case basis.

How do I get a prescription?

PrEP is not an over-the-counter medication. You need a prescription to take it. Most clinics in Montreal can prescribe it. But it might be easier to get at l’Actuel, Quartier Latin, or SIDEP+ Clinic.

If you go to get PrEP, healthcare providers will talk to you about why you want to take it and how to take it. If you’re at risk for HIV, you’ll most likely be able to get a prescription.

How much does PrEP cost?

If you have Régie de l’assurance maladie du Québec or “RAMQ”, the most it will cost you monthly is about $93. Other insurance tends to cover less. Without RAMQ, you’ll probably pay more, depending on your insurance coverage.

How do I take it?

Daily PrEP is a pill you need to take once a day, around the same time. When you miss a dose the pill is less effective.

It is also possible to take PrEP on-demand or intermittently. This is when you take the pills only on the days before and after having sex. It involves 2-1-1 dosing where the person would:

  • Take 2 pills between 2 and 24 hours before sex
  • Then take 1 pill 24 hours after the first dose
  • Take 1 pill another 24 hours later

This type of dosing requires more planning. It’s not recommended for everyone because it has only been tested in populations of gay and bisexual men who have sex with men. You can ask your doctor about PrEP on-demand if you think it might be right for you.

Can I take PrEP with other drugs?

There are a few prescription medications that you can’t take with PrEP. So, it’s a good idea to talk to your doctor before taking new meds or changing the dosage of other ones.

It can also be hard on the liver, so there are a few over-the-counter meds to look out for. Most painkillers, including acetaminophen or “Tylenol”, ibuprofen or “Advil”, and aspirin can cause negative drug interactions if taken with PrEP. If you take these regularly, it may harm your liver.

If you’re taking anything else over the counter, it’s a good idea to talk to the doctor about them before you go on PrEP.

What’s my risk for HIV if I’m on PrEP?

When you take PrEP as prescribed, the risk of getting HIV is almost 0. PrEP has been found to reduce the risk of getting HIV from sex by about 99% and to reduce the risk of getting HIV from injection drug use by at least 74%. But, it doesn’t protect against other STIs. Some STIs can also raise your risk of getting HIV.

More info

Clinique Médicale la Licorne

BERRI-UQAM METRO Clinique Médicale la Licorne offers non-judgemental and confidential health services with a focus on sexual health. Their team includes doctors, nurses, a social…


This resource debunks some myths about HIV that are no longer true in 2015, including that HIV can be detected by testing sooner than expected,…


Related FAQs