Learn what PrEP on-demand is, who it's for, and how it's different from daily PrEP.
PrEP on-demand can be an effective HIV prevention option for those with infrequent, planned sexual habits.
PrEP on-demand (PrOD), like daily PrEP, requires a prescription from an approved PrEP provider in Canada. It’s less frequently prescribed because PrOD requires more planning than daily PrEP.
Patients must start the PrEP on-demand regimen 2-24 hours before a planned sexual encounter.
PrEP on-demand can be an effective HIV prevention option for those with infrequent, planned sexual habits.
PrEP on-demand (PrOD), like daily PrEP, requires a prescription from an approved PrEP provider in Canada. It’s less frequently prescribed because PrOD requires more planning than daily PrEP.
If taken correctly, PrEP on-demand can offer up to 99% protection against HIV during anal sex.
Patients must start the PrEP on-demand regimen 2-24 hours before a planned sexual encounter.
Only Truvada and its generic form can be used for PrEP on-demand. Descovy cannot be prescribed as PrEP on-demand.
PrEP is an acronym for Pre-Exposure Prophylaxis, a daily pill that helps prevent people from contracting HIV when taken correctly.
There are two ways PrEP can be prescribed to be taken:
Daily PrEP is the most common type of PrEP prescription. Simply take 1 PrEP pill every 24 hours for maximum protection. It’s recommended to take daily PrEP at the same time every day.
Most providers in Canada will choose to prescribe daily PrEP, as evidence suggests adherence is more likely to be followed than PrEP on-demand.
PrEP on-demand is less commonly prescribed because it requires careful planning and tracking of sexual activity - and we know sex isn’t always planned. Studies show that PrEP on-demand is effective at preventing HIV, but there is a higher chance of missed doses or low drug levels that might make it less effective than daily PrEP. But if you and your prescriber think it’s right for you, it is a great way to prevent HIV.
PrEP on-demand does not require daily intake. This is ideal for someone who can’t access a sufficient supply of PrEP due to cost or if they have predictable and fluctuating sexual behaviour.
Nicknames for PrEP on-demand include:
•
Intermittent PrEP
•
Non-daily PrEP
•
Event-driven PrEP
•
Off-label PrEP
PrEP on-demand has only been shown to work with the Truvada version of PrEP and its generic forms. Descovy, the newest form of PrEP, has not been approved to use as PrEP on-demand.
PrEP on-demand is often referred to as the 2-1-1 regimen. It consists of a total of 4 pills taken in the following order:
Pills #1-2
Two to twenty-four hours before sexual contact
Pill #3
Twenty-four hours after pills #1-2
Pill #4
Twenty-four hours after pill #3
Take PrEP
pills #1-2
Has sex
Take PrEP
pill #3
Take PrEP
pill #4.
They’ve now completed their PrEP on-demand.
Once you complete the PrEP on-demand routine (ex: Saturday), you have the option to maintain protection by continuing to take PrEP at the same time every day; this is known as daily PrEP.
What if the same person from our previous example wants to have sex on Saturday as well?
The most important thing is that they take PrEP twice before sex and for two days afterwards. Here’s how the updated timeline would work:
Take PrEP pills #1-2
Has sex
Take PrEP pill #3
Take PrEP pill #4
Has sex
Take PrEP pill #5
Take PrEP pill #6. They’ve now completed their PrEP on-demand and can begin daily PrEP.
This person can continue taking a single PrEP pill daily for maximum protection (99%), which is known as daily PrEP. If you want to stop taking PrEP or take a break and start it again later, be sure to take your daily tablet for at least two days after your last sexual encounter.
PrEP on-demand has only been approved to prevent HIV transmission through anal sex - those having vaginal/frontal sex should not consider PrEP on-demand due to differences in the time it takes PrEP to act in body tissues. PrEP on-demand has not been studied for HIV transmission through injection drug use and should not be used for persons with this risk behaviour.
PrEP on-demand can only be taken by patients that are HIV-negative and prescribed to take PrEP this way by their clinician. Whenever possible, prescribing daily PrEP is preferred as this offers the highest rate of HIV protection.
However, PrEP on-demand is still considered to be effective at HIV prevention and is more likely to be a fit for those that:
•
Have less financial ability to pay for daily PrEP
•
Don’t have access to housing or the storage of medication
•
Struggle with daily adherence
•
Have anal sex infrequently and plan their encounters in advance
Book a phone appointmentLESS THAN 10% OF PATIENTS EXPERIENCE SIDE EFFECTS FROM PrEP ON DEMAND.
The most common side effects are nausea and diarrhea. These symptoms might be mild or severe. Other possible side effects include headaches, dizziness, and abdominal pain or cramps (in the stomach).
Although these are experienced more frequently among PrEP on demand than daily PrEP medicine users, the amount of patients that experience side effects is still generally low.
Whether you choose to take PrEP on-demand or daily is your choice. It’s important to understand that most providers in Canada will prescribe daily PrEP when possible, as it’s more effective in preventing HIV and more regulated.
However, if you are considering on-demand PrEP and think it would better suit your current situation, feel free to chat with your PrEP provider. They should be able to advise you on the best dosing schedule and how to best continue preventing HIV in a way that works for you.
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Reviewed by:
Dr. Caley Shukalek
Caley is passionate about evidence-based patient-centred care, including telemedicine that can provide high quality care from wherever a patient may choose.
He helped create Alberta’s PrEP guidelines and works as a specialist in General Internal Medicine with additional training in sexual health, including HIV and sexually transmitted infections.
He holds a Masters of Public Health from Johns Hopkins University, an MD from the University of Calgary and an MSc from the University of Alberta.
