What is PrEP?

Pre-exposure prophylaxis (PrEP) is an additional tool now available to us to help stop ongoing transmission of HIV to 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]

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 both vaginal rings and implant technologies are also in development), and is usually a generic version of Truvada (emtricitabine/tenofovir disoproxil AKA tenofovir disoproxil fumarate or TDF). When used correctly, this 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 only offers protection against HIV, so users need to remain aware about testing regularly for other sexually transmitted infections (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 other STIs.

It is important that people understand that condoms do not offer 100% protection against STIs. It is important that they are aware of their own symptoms and should 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, 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.

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 are dependent on the type of sex the person is having. [2, 4]

Daily dosing, or taking one pill a day is the regimen used. This will offer protection to the user for both vaginal 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 fluids. [1, 4]

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.. One pill of PrEP must be taken daily for at least seven days to allow levels of the drug to reach effective protective levels in the body.

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]

Trans men and trans women can also take PrEP. It will not interact with hormone treatments or cause fat redistribution in the face or body.

Advice is that daily dosing is the best option for trans people who want to use PrEP, whether they are having anal, frontal or neo-vaginal sex. [2]

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.

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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