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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:
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.
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.”
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.”
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:
Regimens commonly used for PEP can include the following:
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.
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.
Resources:
On-demand PEP to prevent HIV infection – CATIE news
Pre-exposure prophylaxis (PrEP) resources and tools – CATIE
Canadian Guideline on HIV Pre-Exposure Prophylaxis and Nonoccupational Postexposure Prophylaxis – Biomedical HIV Prevention Working Group of the CIHR Canadian HIV Trials Network
—Sean R. Hosein
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