On-demand dosing – a term for taking medicines only at times linked to a relevant event.
On-demand dosing for PrEP is also called “event-based dosing” (EBD).
For example, on-demand dosing for PrEP (to prevent HIV transmission) involves taking PrEP before sex and then for several days after sex.
For many years, on-demand dosing referred to 2:1:1 dosing. This was an option for cisgender gay and bisexual men using PrEP. This involves starting with a double dose (two pills), taken 24 to 2 hours before sex, and then single daily doses for the two days after sex.
In 2025, UK (BASHH) and European (EACS) PrEP guidelines included 2:7 on-demand dosing for cisgender women and for transgender and non-binary people.
HIV PCR DNA test – a test that looks for HIV DNA (called integrated HIV) in blood. This is similar to viral load test which usually test for HIV RNA.
open label – this means that a patient in a trial knows which treatment they are taking.
formulation – the physical form that makes an active drug into a medicine.
Different formulations include
- Pills (capsules or tablets).
- Syrups or other oral solutions.
- Injections.
- Powders.
- Creams or lotions.
A co-formulation is when two active drugs are combined. For example: when two active drugs are in the same pill.
CD4 cells are white blood cells in your immune system. CD4 cells signal to CD8 cells to destroy a virus. CD4 cells are also used by HIV as factories to reproduce in.
