Pre-exposure prophylaxis (PrEP) is an addition to the technologies now available to us to help stop ongoing transmission of HIV in people at increased risk of being exposed to and acquiring HIV.
PrEP is a drug taken by HIV-negative people before and after sex that reduces the risk of getting HIV to almost zero. [1, 2, 3 – see references at the bottom of the page]
In England, PrEP is available from the NHS from sexual health clinics as a prescription-only drug.
PrEP is currently given as a tablet. Although long-acting injectable PrEP has been developed, it is not yet available and both vaginal rings and implant technologies are in developmental stages. PrEP is usually a generic version of Truvada (Emtricitabine / Tenofovir Disoproxil aka Tenofovir Disoproxil Fumarate or TDF), which, when used correctly, has been proved to be nearly 100% effective at preventing the acquisition of HIV in users exposed to the virus during sex. It is effective for men and women, although different dosing regimens are recommended. [1, 2, 3, 4]
PrEP offers protection only against HIV, so users need to remain aware about testing regularly for other STIs and continue to use contraception to avoid unplanned pregnancies. Many PrEP users continue to use condoms alongside PrEP for the protective effect that condoms offer against many STIs. It is important that people understand that condoms do not offer 100% protection against STIs and it is best that they are aware of their own symptoms and to seek diagnosis and treatment if they believe they have been exposed to or have acquired an STI.
PrEP offers almost 100% protection against HIV during vaginal, anal and oral sex for users. Acquiring HIV via an oral route is known to be very low risk and much less risk than anal or vaginal routes.
Dr Michael Brady, former Medical Director at Terrence Higgins Trust, says that ‘PrEP is an opportunity for better STI testing.’
He makes these key points:
- PrEP is a fundamental component of HIV prevention
- PrEP is highly effective and safe
- PrEP gives us the opportunity to provide better and more impactful sexual health services
- PrEP is contributing to a drop in HIV infections in men who have sex with men and we need to ensure that ‘all at risk’ benefit from the same effects.
How PrEP is taken
There are different dosing regimens recommended for men and women, with more options available to men. [1, 3, 4]
Dosing regimens for trans men and trans women could be dependent on which hormones they may be taking, which stage of transitioning they are at or are happy being at and the type of sex the person is having. [2, 4] Currently, to make taking PrEP as easy and safe as possible, it is recommended that all trans people follow the one pill a day regimen.
For women using PrEP
Daily dosing, or taking one pill a day, is the regimen used. This will offer protection to the user for both vaginal/frontal and anal sex.
PrEP needs to be taken for seven days before other methods of protection against HIV can be stopped, to allow levels of the drug to reach effective protective levels in the body and vaginal/frontal fluids. [1, 4]
For men taking PrEP
There are three treatment options: daily dosing (one pill a day); on-demand dosing (ODD), also known as event-based dosing (EBD); and four pills a week (sometimes called ‘the Ts and Ss’).
Daily dosing for men is very similar to daily dosing for women, although drug levels build to protective levels much faster in men, so will offer protection after two days of taking the pill daily.
If a man does not want to take pills daily, or if he has sex on an irregular basis, there is the option to use ODD/EBD regimes. ODD/EBD requires the user to know that he will be having sex in the next few hours and the regime is:
- Dose one: two pills taken two to 24 hours before sexual contact. Less than two or more than 24 hours (without continual dosing) will mean the drug will not be at protective levels in the body.
- Dose two: one pill taken 24 hours after dose one.
- Dose three: one pill taken 24 hours after dose two.
Many men have chosen to make taking four pills a week part of their routine, rather than being dependent on knowing when a sexual contact may take place. To make this easier to become routine, it’s known as ‘the Ts and Ss’ because it’s recommended that pills are taken on Tuesday, Thursday, Saturday and Sunday.
All of these four-pill regimes provide a sufficient level of drug in the person’s system to offer protection against HIV. [1, 2, 3, 4]
For trans people taking PrEP
Trans men and trans women can also take PrEP, and it will not interact with any hormone treatments, or cause fat redistribution in the face or body.
Advice is that daily dosing is the best option for any trans people who want to use PrEP, whether they are having anal, frontal or neo-vaginal sex. [2]
Missing a dose
People who take PrEP and miss a dose will still have high levels of the drug(s) in their bodies and therefore still have high levels of protection.
The best advice to give to people in this case is to take another dose when they remember and then continue with their usual dosing regimen.
Next: Why PrEP, who is it for and why we want to reach the communities we do.
References
1: Botswana TDF2 (Truvada) 2011; Partners PrEP Trial 2013; Bangkok PrEP Trial 2013; PrEP Impact Trial England 2017.
2: iPREX 2010; Proud Study 2014; PrEP Impact Trial England 2017.
3: iPREX 2010; Proud Study 2014; iPERGAY 2014; PrEP Impact Trial England 2017.
4: Proud Study 2014; iPERGAY 2014; PrEP Impact Trial England 2017.