Intermittent PrEP also called “PrEP on demand” is a way to take PrEP medication if you find your level of sexual activity is infrequent, your risk of exposure is only for short periods of time – such as travel, or you have significant side effects from PrEP that make taking daily tablets undesirable. (1)
The iPerGay study showed that short term use of Truvada PrEP can be effective using the following schedule (2):
- Take TWO Truvada pills from 24 hours to 2 hours in advance of an anticipated exposure to HIV.
- If you do have sex that risks exposure, then take another pill 24 hours after the first dose and another one the day after that – again 24 hours after the previous pill.
- If, however, you have sex that risks exposure again at some point in the two days after the first sex – then keep on taking one Truvada pill per day, until two days (48 hours) after your last sex. Only then stop.
The following video helps explain how to take intermittent PrEP using 3 different examples
Intermittent PrEP Dosing
In A Nutshell:
Take 2 tablets of Truvada 2-24 before sex, then take one tablet every 24h after the first dose till you’ve had 2 days (48h) free from sexual activity.
Time Intervals Between Intermittent Doses
If you have finished your episode of PrEP and then potential sex come up how do you proceed?
- If it’s less than 7 days since your last tablet you don’t need to take the double starting tablets, just one.
- If it’s been more than 7 days since the last dose of PrEP you need to start again with the 2 tablets of Truvada
From this point it’s continue as above, one tablet of PrEP every 24 hours till 48 hours has passed free of sex.
Currently on demand PrEP research has looked at gay males and trans women. (3) The Australian PrEP Guidelines note:
It is important to emphasise that on-demand PrEP should not be used in cis-gender women or heterosexual men owing to a lack of data about its efficacy in these populations.
- Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine HIV pre-exposure prophylaxis: clinical guidelines. Update April 2018
- Intermittent PrEP – Do you have to take it every day?
- Aides Guide To Talking PrEP
- Antoni G , Tremblay C , Charreau , et al. On-demand PrEP with TDF/FTC remains highly effective among MSM with infrequent sexual intercourse: a sub-study of the ANRS IPERGAY trial. International AIDS Society Conference on HIV Science July 2017; Paris, France , Abstract TUAC0102
So, intermittent dosing is per episode taking of PrEP, so you really only take the PrEP during a period where you are having sexual intercourse that could lead to a potential transmission of HIV.
So, I wanted to explain the process. It’s quite straightforward, basically you start by taking two tables of PrEP, two to twenty-four hours before you think you’re going to be having sexual activity. Then, if you do have sexual activity you take a single tablet of PrEP every 24 hours until there has been 48 hours of intercourse free time.
Say for example you’ve heard from a friend and you’re looking forward to catching up i think them on Saturday. Let’s have a look at a calendar and see how this would work. So, Saturday morning you hear from your friend, it’s about two to twenty-four hours before you’re going to catch up with your friend, so you would take your two tablets of PrEP, say Saturday morning.
Then, Saturday evening you catch up with your friend and you have sexual intercourse. You then take one tablet of Truvada, 24 hours after you took these first two tablets, and then you have a second tablet of Truvada, again 24 hours after this tablet. So you’ve had two tablets, and then the next tablet 24 hours later, and another tablet 24 hours later.
So if you’ve only had the sex on the Saturday, you would stop taking the PrEP on the Monday. If you had sex on Saturday, and on Sunday, then you would need to take an additional tablet of PrEP, because we want to make sure that we have 48 hours free from sexual activity.
Say for example you took your two tablets and had sex on the Saturday, then you didn’t have sex on the Sunday, but you did have sex on the Monday. Again, you need the 48 hours of sexual activity free, and that’s a single tablet of PrEP every 24 hours. Sex on Saturday, no sex on Sunday, but you did have sex on the Monday, then you just need to make sure that you take a tablet of PrEP on the Tuesday and a tablet of PrEP on the Wednesday.
Of course, be sure to talk with your doctor about whether intermittent dosing is for you. It is generally good for most people, the only people who should not be on intermittent dosing are people who are living with hepatitis B infection, because going on and off of the Tenofovir and Emtricitabine can effect the hepatitis B virus. If you would like to learn more about intermittent dosing and prep, be sure to talk with your doctor to make sure you have a full understanding on how it works. I hope this was helpful.