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  • Post-exposure prophylaxis (PEP) can prevent HIV if initiated within 72 hours
  • Some Toronto clinicians prescribed PEP in advance to reduce delays in initiation
  • "PEP in Pocket" (PIP) may be an alternative to PrEP for people with fewer exposures

Research has found that when used as directed, pre-exposure prophylaxis (PrEP) is highly effective at reducing the risk of HIV infection. PrEP consists of a pill containing two anti-HIV medicines—tenofovir DF and FTC—sold as Truvada; it is also available in generic formulations. The most widely studied schedule of PrEP is one pill taken once daily.

An alternative schedule called "on-demand" PrEP has been tested in gay men and consists of the following:

  • two pills taken two to 24 hours prior to sex, followed by one pill daily until 48 hours after the last episode of sex

Regardless of the schedule of PrEP (daily or on-demand), testing for HIV and other sexually transmitted infections (STIs) prior to initiating PrEP and at regular intervals after PrEP initiation is necessary. Health assessments are also done and vaccination against hepatitis A and B viruses in people who do not have immunity them can be helpful.

Another HIV prevention intervention is PEP (post-exposure prophylaxis). This involves initiating a course of HIV treatment within 72 hours of possible exposure to HIV and taking treatment for 28 consecutive days.

Gaps in HIV prevention

Infectious disease specialist Isaac Bogoch, MD, and colleagues at the University of Toronto have noted that for some people who have infrequent sexual exposure to HIV, the cost of daily PrEP and remembering to take it can be burdensome. On-demand PrEP has been shown to be effective with about 15 tablets taken over the course of a month (in these cases, men were having several sexual encounters). However, in the October 2019 issue of the medical journal Lancet Public Health, Dr. Bogoch and colleagues make the following statement:

“…it is unclear how effective on-demand PrEP would be for individuals with lower usage because of less frequent HIV exposures. On-demand PrEP is also not helpful for people who do not proactively anticipate a potential HIV exposure. PEP is a retroactive approach to HIV prevention and is helpful if accessed within a 72-hour window, but there are substantial issues with timely access to medications, adherence to clinic appointments and adherence to the 28-day course of medications.”

Narrowing the gaps

To shrink the gaps in HIV prevention, particularly for people who have a much lower rate of exposure to HIV (between one and four exposures per year) than commonly reported in clinical trials of PrEP, Dr. Bogoch has developed another approach called PIP (PEP in Pocket). He says that PIP involves the following:

 “…providing selected patients with a 28-day prescription for PEP before an exposure occurs. Patients are counselled to obtain the medications and keep them accessible in case of an exposure. Should there be an exposure, patients are advised to initiate medications as soon as possible (and within a 72-hour window) and to come to the clinic within the first week of initiating medications for clinical assessment and baseline HIV screening. Patients are typically followed at six-month intervals for routine screening for HIV and sexually transmitted infections, or sooner based on their exposure history.”

Advantages of PIP

According to Dr. Bogoch, “PIP enables immediate access to [HIV treatment] and might reduce the need for time-sensitive emergency department or clinic visits. PIP empowers patients by providing a degree of autonomy over their care and might also alleviate anxiety associated with potential [HIV] exposures.” These points are noteworthy because visits to overcrowded emergency departments filled with distressed people can be stressful and there is usually a waiting period of at least several hours before patients can see a doctor.

Dr. Bogoch sees PIP as an option for the following patients:

  • those with a low frequency of potential exposure to HIV (between one and four exposures a year)
  • those who have sought PEP in the past
  • those who have sought PrEP in the past
  • those who are health literate

Hooking up

Regimens commonly used for PEP can include the following:

  • Truvada + Tivicay (dolutegravir) – two pills daily
  • Biktarvy (tenofovir alafenamide + FTC + bictegravir) – one pill daily

Both regimens are generally well tolerated. However, these pills can be expensive, so Dr. Bogoch enlists the help of social workers to help connect patients to subsidized access.

Bear in mind

Although Dr. Bogoch finds PrEP to be a widely used and effective form of HIV prevention, he emphasizes that PrEP taken daily or on-demand may not be ideal for people with infrequent exposure to HIV. He sees PIP as a form of tailored HIV prevention for people who have infrequent exposure to HIV. Preliminary analysis from Dr. Bogoch’s clinic suggests that PIP has been effective in preventing HIV infection.


On-demand PEP to prevent HIV infectionCATIE news

Pre-exposure prophylaxis (PrEP) resources and toolsCATIE

Canadian Guideline on HIV Pre-Exposure Prophylaxis and Nonoccupational Postexposure ProphylaxisBiomedical HIV Prevention Working Group of the CIHR Canadian HIV Trials Network

—Sean R. Hosein


  1. Heendeniya A, Bogoch II. HIV prevention with post-exposure prophylaxis-in-pocket. Lancet Public Health. 2019 Oct;4(10):e494.
  2. Tumarkin E, Heendeniya A, Murphy P, et al. Brief Report: HIV postexposure prophylaxis-in-pocket ("PIP") for individuals with low-frequency, high-risk HIV exposures. JAIDS. 2018 May 1;78(1):20-22.
  3. Ismail MF, Wong DK, Bogoch II. The role for hepatitis A vaccination in HIV pre-exposure prophylaxis. AIDS. 2018 Mar 13;32(5):675-676.
  4. Molina JM, Charreau I, Spire B, et al. Efficacy, safety, and effect on sexual behaviour of on-demand pre-exposure prophylaxis for HIV in men who have sex with men: an observational cohort study. Lancet HIV. 2017 Sep;4(9):e402-e410.
  5. Tan DH. PrEP on demand or every day? Lancet HIV. 2017 Sep;4(9):e379-e380.