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PrEP basics

What is PrEP?

PrEP is used by people who are HIV negative to help prevent them from getting HIV. PrEP stands for pre-exposure prophylaxis. It involves taking a prescription pill that contains two medications, emtricitabine and tenofovir. It is very important to take the pill as prescribed for it to work.

Taking PrEP also involves seeing a doctor or nurse every three months for HIV testing, screening for other sexually transmitted infections (STIs), monitoring for possible side effects, and ongoing support.

Who is PrEP for?

PrEP is for people who are at ongoing risk for HIV. PrEP may be a good option for anyone who is HIV negative and:

  • sometimes has vaginal or anal sex without using a condom and doesn’t know the current HIV status of one or more of their sex partners
  • has a sex partner who is HIV positive and is not maintaining an undetectable viral load while on treatment
  • sometimes uses injection drugs and shares needles

People who are interested in taking PrEP should talk to a medical professional to see if PrEP is right for them.

Who can prescribe PrEP?

A prescription is required to get PrEP. It is usually prescribed by a medical doctor or nurse practitioner, and some pharmacists may also be able to prescribe it. There are national PrEP guidelines in Canada to inform healthcare providers on how to provide PrEP. Some provinces also have their own PrEP guidelines.

An online continuing medical education module has been produced to help healthcare providers learn how to provide PrEP care in line with the Canadian national guidelines.

What is the difference between PrEP and PEP?

Both PrEP and PEP involve taking HIV medications to help prevent HIV but they are different. PrEP involves taking two HIV medications on an ongoing basis, starting before and continuing after a potential exposure to HIV. This is different from PEP (post-exposure prophylaxis), which consists of a combination of HIV medications (typically three) that an HIV-negative person takes to reduce their risk of getting HIV after a potential exposure to HIV. PEP should be started as soon as possible, but definitely within 72 hours of being potentially exposed to HIV. The prescription drugs used for PEP need to be taken every day for four full weeks (28 days).

Common concerns about PrEP

Why do we need PrEP when people can just use condoms?

The more HIV prevention options people have the easier it is to find one that is right for them. While condoms have been the cornerstone of HIV prevention, not everyone uses condoms every time they have sex. People may not use condoms for a variety of reasons. For example, some people have a hard time talking to their partners about using condoms, and for others condoms decrease sexual functioning or their enjoyment of sex. PrEP is an additional HIV prevention tool that some people may prefer over condoms. It is not meant to replace condoms for everyone.

Does PrEP discourage condom use and lead to more risk for STIs?

PrEP is intended for people who are at ongoing risk for HIV. This includes people who do not consistently use condoms and may already be at risk for STIs. Research shows that condom use has been declining in Canada over the past two decades, even before PrEP became available. PrEP is a tool that can help fill this gap by giving people another highly effective HIV prevention option. Research shows that after they start PrEP some people become less cautious and do things that increase their chances of getting an STI, but many do not. People who are taking PrEP should receive counselling on how to reduce their risks, which may encourage them to use condoms in situations where there might be a risk for STIs. People who are taking PrEP also receive routine STI testing and treatment, which keeps them healthy and can also help prevent them from passing STIs to others.

Should a person who is using PrEP also use condoms and other prevention strategies?

Each individual has the right to decide whether they want to use PrEP alone or with other prevention strategies. People who are taking PrEP should be made aware that although PrEP is highly effective at preventing HIV, it does not protect against other STIs or other infections such as hepatitis C. It also does not prevent pregnancy. Many people do choose to use additional prevention strategies when taking PrEP, such as using condoms. Ultimately, however, whether or not to use additional prevention strategies while taking PrEP is an individual’s personal choice. Counselling on how to reduce their risks allows people to make informed decisions about the level of risk that they and their partner(s) are comfortable taking.

Safety, drug interactions and situations when people should not take PrEP

What are the possible side effects of PrEP?

PrEP is safe and usually well tolerated, and most people who take it report no side effects. Some people experience side effects such as nausea, diarrhea or fatigue, but these usually go away on their own within a few days to weeks as the body adjusts to the medication. For some people, PrEP can affect kidney and liver function, and bone density. If this happens, organ function and bone density usually return to normal after PrEP is stopped. It is important that healthcare providers monitor kidney function and check for other potential drug effects in people taking PrEP.

Do the drugs in PrEP interact with any other medications or recreational drugs?

Anyone who is considering taking PrEP should talk to their healthcare provider about any medications or recreational drugs that they are taking. Most commonly used medications and recreational drugs are not known to interact with the drugs in PrEP, but PrEP does interact with some medications. The University of Liverpool maintains a list of drugs that may interact with PrEP.

Who should not take PrEP?

People who have HIV should not take PrEP. The drugs in PrEP can be used for HIV treatment, but only in combination with other HIV drugs. If a person already has HIV and takes PrEP, there is a risk of developing drug resistance, which can complicate future treatment options. For this reason, it is very important that people be tested for HIV before starting PrEP and at every follow-up appointment. Anyone who is considering taking PrEP should discuss any pre-existing health conditions with their healthcare provider, especially those that affect their kidney, liver or bones (e.g., hepatitis B or C, or osteoporosis). These conditions do not necessarily prevent a person from taking PrEP, but they might require special considerations or additional monitoring.

How PrEP works in the body

How does PrEP work to prevent HIV?

To understand how PrEP works in the body, let’s first look at how HIV infections can happen in a person who is not taking PrEP.

HIV infection can happen if HIV gains entry into the body through blood-to-blood contact or through mucous membranes such as within the genital tract and rectum. Once in the body, HIV targets the CD4 cells in the person’s immune system and begins to replicate within them, creating millions of copies of itself. These copies then go out into the body where they find more CD4 cells, which they use to make even more copies. The person’s immune system will try to clear the virus, but if the body’s immune cells can’t keep up then the HIV infection spreads to other parts of the body, such as the lymph nodes, the gut and other organs. At this stage the infection becomes permanent.

In people who take PrEP consistently and correctly, drug levels reach high concentrations in the places where HIV can enter the body (e.g., the bloodstream, genital and rectal tissues). The drugs in PrEP prevent HIV from making copies of itself in CD4 cells. Since HIV can’t replicate, the immune system can clear the virus from the body, thus preventing a permanent infection. This is why it is so important to take PrEP as prescribed to ensure that there is enough drug in the body to stop HIV from replicating.

When does PrEP fail to prevent HIV?

Most of the time when a person who is taking PrEP gets HIV, it is because they were not taking their pills as prescribed. If pills are not taken as prescribed, drug levels in the body may not be high enough to prevent HIV infection.

In some extremely rare cases, people have got HIV while taking PrEP as prescribed. In most of these cases, the person was exposed to a strain of HIV that was resistant to the medications in PrEP. So far there have only been a few reported cases of PrEP failure when a person was taking PrEP as prescribed.

How long does it take for PrEP to provide protection after a person starts taking it?

To provide protection, the medications in PrEP need to reach and stay at certain levels in the blood and mucous membranes (e.g., in the rectum and vagina). It takes about one week of daily PrEP for it to provide protection from HIV when taken as prescribed. For men who have sex with men who take PrEP on an on-demand schedule, PrEP begins to provide protection two hours after the first two pills are taken.

What happens if a person forgets to take one or more of their pills?

Taking pills as prescribed is very important for PrEP to work. People should aim to take PrEP at roughly the same time every day, but occasionally taking a pill at a different time in the day should not be a problem. If a person forgets to take their pill one day, they should still only take one pill the next day. People should not take extra doses at one time to make up for missed pills. When pills are missed, it may be a good idea to use additional HIV prevention tools for a week or so because PrEP may not be providing full protection. This is particularly true for women and trans guys who have vaginal (frontal) sex because adherence is very important to maintain protective drug levels in the vagina (front hole). Research shows that drug levels can remain protective in men who have sex with men who take daily PrEP even when they occasionally miss a few doses.

If a person’s risk changes, can they safely stop taking PrEP?

Yes. People can take PrEP for as long or as short a time as they like. Many people only use PrEP for a period in their life when they need it, based on their risk for HIV at the time. People who want to stop taking PrEP should talk to a healthcare provider to find out how many days they should continue taking  PrEP after their last potential exposure and to discuss additional prevention options to use while tapering off PrEP.

Special considerations for specific populations

Are there any special considerations for trans people who are considering taking PrEP?

Daily PrEP can be used by people of all genders. Experts believe that PrEP can effectively prevent HIV in trans people and that the drugs in PrEP are unlikely to interfere with the hormones that some trans people take; however, this has not been well studied. There is some evidence that feminizing hormones that some trans women take can lower the amount of PrEP drugs in the body by a small amount, although drug levels still remain high enough to protect against HIV. Because of this potential interaction it is recommended that trans women should take PrEP daily rather than on-demand. Trans men who have frontal sex should also take PrEP daily because daily dosing is needed to keep drug levels high in the front hole or vagina. There is currently no evidence showing how well PrEP works for people who have undergone  gender affirming surgeries.

Are there any special considerations for youth who are considering taking PrEP?

PrEP is approved by Health Canada for people 18 years of age and older, but a healthcare provider can choose to prescribe it to a person who is under 18.

Experts believe that PrEP is just as effective for youth as it is for adults, although there hasn’t been a study looking at effectiveness specifically among youth. Studies have shown that PrEP appears to be safe for youth to take. However, there is some concern that PrEP could increase risk for bone problems later in life. This is because bone mass generally peaks in young adulthood, and peak bone mass is a predictor of bone health later in life. Young people who are considering taking PrEP can discuss these concerns with a healthcare provider when deciding if PrEP is right for them.

Are there any special considerations for people who are pregnant, breastfeeding (chestfeeding) or planning to have a baby and are considering taking PrEP?

Daily PrEP is safe to take while pregnant and breastfeeding (chestfeeding), for both the parent and the baby. PrEP may also be an HIV prevention option for couples who want to have a baby if one partner is HIV positive and not on successful treatment. People who are pregnant, breastfeeding (chestfeeding) or planning to have a baby should discuss their options with a healthcare provider.

Accessing PrEP and remembering to take pills

What are some tips for talking with a healthcare provider about PrEP?

The first step is to find a healthcare provider the person feels comfortable talking with honestly about their sexual behaviours, their drug use and their desire to use PrEP. Some people may feel comfortable talking to their family doctor or nurse practitioner while others may want to find a healthcare provider who has experience prescribing PrEP. Sexual health clinics or HIV organizations may be able to help connect people with appropriate healthcare providers in their area.

It is a good idea for people who want to take PrEP to do some research before visiting their healthcare provider. PrEP was approved relatively recently in Canada, and some healthcare providers do not know much about it. Going into an appointment being well-informed about PrEP can help a person to explain to their healthcare provider why they think PrEP would be a good option for them. Before talking to a healthcare provider about PrEP, it is a good idea for a person to write down any questions that they have so that they can ask them at the appointment.

What options are available to help cover the cost of PrEP?

The cost of PrEP is covered by most public and some private health insurance plans in Canada. Without coverage, daily PrEP costs about $250 per month. People who want to take PrEP can contact a doctor, pharmacist or HIV organization to learn about ways to cover the cost. A list of national, provincial and territorial programs that cover the cost of PrEP is available here.

What tools and strategies can help a person to remember to take the pills?

Some people find it difficult to remember to take PrEP as prescribed. It is a good idea to try to form a habit of taking daily PrEP at the same time every day. For example, some people might take PrEP every morning with breakfast, or every night before bed. People who take other daily medications (such as a daily vitamin, birth control or methadone) can take PrEP at the same time as those medications. Some people might benefit from setting an alarm to remind themselves to take medications. There are also phone apps that can help a person remember to take pills.

For men who have sex with men who are thinking about taking on-demand PrEP, it is worth considering which dosing schedule they are likely to adhere to. Some people might find it easier to remember to take a pill every day as opposed to on an on-demand schedule.

More Resources

What resources are available for people who are interested in taking PrEP and want to learn more?

A list of resources for clients is available at: www.catie.ca/prep/clients

What resources are available for service providers who want to learn more about PrEP?

A list of resources for service providers is available at: www.catie.ca/prep/cbo

Where can I find clinical guidelines for PrEP?

National and provincial guidelines are available at: www.catie.ca/prep/clinical