Incidence of HIV has been rising in Canada. The Public Health Agency of Canada estimated 2242 new HIV infections in 2018, which highlights the need for comprehensive prevention strategies. (1) Pre-exposure prophylaxis (PrEP) is an important means of preventing acquisition of HIV; however, it is underused. (2-4) Although generalists (e.g., family physicians, nurse practitioners and general internists) could play a vital role in implementing PrEP, a recent small survey of general practitioners in Nova Scotia found that most did not prescribe PrEP. (5) We describe PrEP for HIV and discuss current uptake and potential barriers to its use, as well as the approach to prescribing PrEP (Box 1).
What is pre-exposure prophylaxis for HIV?
Pre-exposure prophylaxis for HIV is the use of antiretroviral agents by people who are HIV negative that begins before and continues after potential HIV exposures to prevent acquisition of HIV. (6,7) It can be taken daily or on demand before an anticipated exposure. (6,7) Pre-exposure prophylaxis is best used as part of a comprehensive HIV and sexual health strategy that includes harm-reduction education, screening for sexually transmitted infections (STIs), reproductive and mental health care, and attention to co-occurring conditions such as hepatitis B and depression.
How effective is pre-exposure prophylaxis for HIV?
High-quality evidence from randomized controlled trials (RCTs) and observational studies has shown that use of daily PrEP among gay, bisexual and other men who have sex with men (GBM) is associated with almost 100% prevention of HIV acquisition when adherence is high. (8-10) High-quality evidence has shown that efficacy of PrEP is as high as 95% for heterosexual exposure, depending on adherence. (11-13) A 2013 RCT involving people who inject drugs in Bangkok, Thailand, (the Bangkok Tenofovir Study) showed 48.9% efficacy of PrEP but had very low adherence among participants; efficacy increased to 74% among a subgroup of participants who had detectable antiviral levels. (14) Research in all populations has shown the importance of adherence for efficacy, and observational data have shown high effectiveness in real-world settings, with breakthrough infections being uncommon. (15) Uptake of PrEP has been clearly associated with a decline in HIV diagnoses at the population level. (16,17)
The Intervention Preventive de l'Exposition aux Risques avec et pour les Gays (IPERGAY) trial showed that on-demand PrEP is efficacious in GBM, with a reduction in risk of acquiring HIV of 86%; only 2 breakthrough infections occurred in 2 participants who were not adherent to the prophylaxis regimen. (6,18) Participants took a median of 15 pills per month and, although a post hoc analysis showed similar efficacy in participants using fewer than 15 pills per month, there remain modest data on effectiveness in those with more sporadic exposures. (18,19)
Box 1: Evidence used in this review We conducted a PubMed search of original research and review articles published from January 2017 to January 2021, using the terms "HIV PrEP" or "HIV pre-exposure prophylaxis" and "Canada" or "Canadian." We used this time frame because the Canadian preexposure prophylaxis (PrEP) guideline was released in 2017....