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  • Canadian expert panel proposes criteria for clinicians to identify individuals who would benefit from PrEP or PEP for HIV prevention.
  • Guidelines offer practical advice for patient care and monitoring, including adherence support and screening for sexually transmitted infections.
  • Panel outlines dosing options and drug recommendations, including the option of “on-demand” PrEP for men who have sex with men.

A panel of Canadian experts in biomedical HIV prevention has developed guidelines to help healthcare providers deploy two important prevention technologies—PrEP (pre-exposure prophylaxis) and PEP (post-exposure prophylaxis)—in cases of possible exposure to HIV through sex or substance use. The well-crafted guidelines are chock-full of useful information for doctors, nurses, nurse practitioners, pharmacists and service providers and should see widespread use.

About PrEP and PEP

PrEP involves taking anti-HIV medicines, usually daily, as part of a package of options to reduce the risk of HIV infection.

PEP is initiated as soon as possible (within 72 hours) after possible exposure to HIV. A course of PEP lasts for 28 consecutive days. PEP that is meant for cases of possible exposure through condomless sex and/or sharing equipment for substance use is sometimes referred to as non-occupational PEP or nPEP.

The guidelines recommend that PrEP and nPEP be part of a combination prevention strategy that also includes:

  • risk-reduction counselling
  • use of condoms
  • regular HIV testing
  • screening for sexually transmitted infections (STIs) and, when necessary, treatment

Who are the guidelines for?

The guidelines are intended to support a broad range of clinicians to provide PrEP and nPEP, including the following specialties:

  • emergency medicine
  • primary care
  • infectious diseases
  • nursing
  • pharmacy

As well, the panel stated that “non-prescribing healthcare and service providers should be encouraged to play roles in PrEP and nPEP delivery including clinical monitoring, STI screening and management, risk reduction counseling and adherence support.”

When is HIV transmissible?

The guidelines distinguish between three different categories of HIV transmission risk as follows:

  • significant
  • low but not zero
  • negligible/none

The guidelines provide examples of these different categories of HIV transmission risk (in the context of exposure during sex and sharing of equipment for substance use) to help guide clinical decision-making. According to the guidelines, there is a significant risk of transmissible HIV in the following circumstances when condomless sex has occurred:

  • a person is HIV+ and is viremic (that is, has a detectable viral load)
  • the HIV status of a person is unknown and they belong to a priority population with high HIV prevalence compared to the general population (such as men who have sex with men or people who inject drugs)

However, according to the guidelines, there is negligible or no risk of transmissible HIV from a person who:

  • is confirmed HIV negative
  • is HIV positive with confirmed undetectable viral load and no sexually transmitted infections present at time of exposure

When is PrEP indicated?

In gay, bisexual men and other men who have sex with men (MSM), and transgender women

PrEP is recommended for MSM and transgender women who report condomless anal sex and who have any of following additional risk factors:

  • rectal gonorrhea or other sexually transmitted bacterial infections of the rectum
  • infectious syphilis
  • more than one course of nPEP
  • an HIV-positive partner who has a significant risk of transmissible HIV
  • a high score on a validated HIV risk-assessment scale

PrEP is not recommended in the context of a closed, stable relationship with single partner if there is a negligible risk of transmissible HIV.

In heterosexual people

Because HIV prevalence in the general Canadian heterosexual population is low, the guidelines focus their recommendations on heterosexual people in known serodiscordant relationships where one partner is HIV positive and the other is HIV negative. If the HIV-positive partner has a significant risk of transmissible HIV and condomless vaginal or anal sex is also reported, then PrEP is recommended for the HIV-negative partner.

In people who inject drugs

PrEP may be considered for people who inject drugs if they are sharing equipment for using drugs with someone who has a non-negligible risk of HIV infection. Sexual risk may also be an indication for PrEP in this population. The panel noted that the evidence for the use of PrEP among people who inject drugs is weak. A clinical trial of PrEP in people who inject drugs found that daily oral PrEP resulted in a significantly reduced risk of HIV infection in people who had detectable levels of tenofovir in their blood (presumably due to good adherence). The guidelines state that it is not possible to “distinguish PrEP efficacy attributable to the prevention of sexual vs. [injected] HIV transmission” in that study.

Recommended drugs and schedules for PrEP

The guidelines recommend the use of the following combination of two drugs:

  • a tablet containing a fixed dose of tenofovir + emtricitabine (TDF/FTC)

According to the guidelines, “daily TDF/FTC is the PrEP regimen of choice because it has been the most widely evaluated in high quality studies.”

For MSM only, an alternative “on demand” regimen may be considered. This alternative recommendation is based on the results of a randomized, placebo-controlled trial among MSM.

The document also states that the formulation of tenofovir that should be used for PrEP is tenofovir DF (disoproxil fumarate).

When is nPEP indicated?

The guidelines recommend nPEP for HIV-negative people “who present no later than 72 hours after an exposure that is moderate- or high-risk for HIV transmission with a person who has a significant risk of having transmissible HIV.” The guidelines state that nPEP may be considered when the person has a low but non-negligible risk of having transmissible HIV.

The guidelines recommend several first-line and alternative regimens based on data regarding rates of regimen completion and associated side effects.

Practical advice

The guidelines provide extensive practical advice to clinicians on a range of issues including:

  • risk assessment
  • how to evaluate and monitor people on PrEP or nPEP
  • screening for sexually transmitted infections
  • adherence support
  • considerations for special populations

In addition to raising biomedical and behavioural issues, the guidelines alert care providers to issues that may predispose some people to risk-taking such as depression and addiction.

A vision for the future

The guidelines will fill a growing need as they educate and enable a range of care providers to help play a role in reducing the spread of HIV. The authors of the guidelines stated that nPEP and PrEP are “two important HIV prevention strategies that should be considered standard of care and implemented as components of a comprehensive response to the epidemic.”

The guidelines will be updated when new products for PrEP are approved by Health Canada.


—Sean R. Hosein


Tan Darrell HS, Hull MW, Yoong D, et al. Canadian guidelines on HIV pre-exposure prophylaxis and non-occupational post-exposure prophylaxis. CMAJ. 2017;189(47):E1448–E1458. Available from: http://www.cmaj.ca/content/189/47/E1448