spinal tap – See lumbar puncture.
Glossary
Selected words and phrases
NNRTI – Non-Nucleoside Reverse Transcriptase Inhibitor, a type of HIV drug – also called ‘non-nuke’.
Efavirenz, nevirapine, rilpivirine, etravirine and doravirine are all NNRTIs.
viral rebound – when your viral load has been undetectable (under 50 copies/mL) and then becomes detectable. Sometimes viral rebound can be a lab error, sometimes a small temporary blip, and sometimes a real rebound that shows your virus may have developed resistance to one or more of the drugs in a combination treatment. See: virological failure.
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.
antiretrovirals – the common name for any HIV drugs. HIV is a retrovirus, so drugs to fight HIV are called antiretrovirals. Also abbreviated to ARVs.