This dosing option is only suitable for anal sex, not vaginal or frontal sex.
If you’re using On Demand, it’s really important not to miss any doses.
On Demand dosing is as effective as daily PrEP for anal sex.
If you know that you might have condomless sex 24 hours in advance:
- take 2 pills 2 – 24 hours before sex
- take 1 pill 24 hours later
- take 1 more pill 24 hours after that
If you’re having sex for an extended period of time, perhaps over a few days or a weekend, continue to take a pill every 24 hours until you have 2 sex-free days.
This option is not recommended if you have an active hepatitis B infection. The drugs in PrEP also supress the hepatitis B virus and so starting and stopping PrEP can cause viral flare-ups and liver inflammation.