4 pills per week — also known as ‘the Ts and Ss’

This dosing option is only suitable for anal sex, not vaginal or frontal sex.

If you intend to use this regimen, then we advise that you take a daily dose for the first 7 days before switching to  T’s and S’s and dropping down to 4 pills per week.

4 pills per week usually involves taking a pill on Tuesday, Thursday, Saturday and Sunday — that’s why it’s called ‘the Ts and Ss’.

This option has several benefits:

  • If you only have sex once or twice a month, you might not want to take a pill every day. You might feel it’s more pills than you need to protect you for these 1 or 2 events.
  • 4 pills per week will maintain a good baseline of drug in your system and you can choose to move up to 7 pills per week when you know you’re in a more sexually active period.
  • Some people using PrEP On Demand find that they might be taking 4 pills per week most weeks of the month and so opt for structuring this into the Ts and Ss instead.
  • If you are paying for your PrEP, it costs you less because it reduces the number of pills you take each month by almost half — which reduces the cost per month by almost half too.

Though these dosing options don’t seem to follow a simple rule, they are based on study data.