Tenofovir disoproxil / emtricitabine for PrEP

What is PrEP?

PrEP stand for pre-exposure prophylaxis. This means preventing HIV by taking anti-HIV drugs.

PrEP allows you to have sex you want without the fear of contracting HIV.

How does it work?

The anti-HIV drugs in PrEP stop HIV from entering your cells. You need to take PrEP every day or take several doses before and after sex to make sure that the drugs maintain high levels in your bloodstream to prevent HIV infection.

What is tenofovir disoproxil / emtricitabine?

The most widely used type of PrEP is a tablet which contains two anti-HIV drugs, tenofovir disoproxil and emtricitabine. This tablet was originally marketed under the name Truvada, but generic versions are now available from other manufacturers.

The same tablet can also be used by people living with HIV as part of their treatment, in combination with another medication. This is different from PrEP. There’s more information about this on another page.

What other types of PrEP are there?

Tenofovir alafenamide / emtricitabine (Descovy) is an alternative tablet. If you have concerns about your kidney or bone health, this may be more suitable. There’s more information about this on another page.

Different PrEP drugs can also be taken as an injection or in a vaginal ring.

These other types of PrEP are not available in all countries.

What’s the difference between PrEP and PEP?

You start to take pre-exposure prophylaxis (PrEP) before you are exposed to HIV and continue to take it for as long as you need it, to protect against infection. You take post-exposure prophylaxis (PEP) after you have been exposed to HIV, for a fixed period of one month.

Effectiveness

In gay and bisexual men, three large studies have shown that taking tenofovir disoproxil and emtricitabine as PrEP every day, or when needed, reduced the risk of acquiring HIV by 86% - 87%.

In women and their male partners, daily PrEP reduced the risk of acquiring HIV by 75% - 77% in two large studies. But several studies have failed to show a protective effect of tenofovir disoproxil and emtricitabine PrEP in women. The common factor explaining the lack of protection in these studies was missing doses of PrEP.

Is this type of PrEP available to me?

Tenofovir disoproxil / emtricitabine is available in many countries. You can check the PrEPWatch website to see if it approved for use in your country.

Services which provide HIV testing, treatment for sexually transmitted infections or treatment for HIV may also provide PrEP – or have information on local services which do.

Tests before starting PrEP

You need to have an HIV antibody / antigen test to check that you don’t have HIV already. If you have HIV, taking PrEP will lead to your HIV developing resistance to the drugs in PrEP. As this would mean that these drugs would not work properly as HIV treatment, it’s important to avoid this.

It’s usually recommended to have a blood test for kidney function. In high-income countries, all PrEP users should have this test. In some low and middle income countries, it may only be available to people over the age of 30 – this is because kidney problems are unusual in younger people.

A very small proportion of people are unable to take tenofovir disoproxil because they have weakened kidney function. If this is the case, you may be offered another type of PrEP pill containing tenofovir alafenamide.

You should also be tested for hepatitis B. Tenofovir is active against hepatitis B virus, so it is important to know how to take PrEP safely if you have hepatitis B (see below).

How to take PrEP

For PrEP to work, it needs to be taken correctly. This means having enough PrEP in your body at the times when you need protection.

PrEP can be taken for short or long periods of time, depending on the sex you are having, how comfortable you are with PrEP and what helps you avoid missing doses. As a PrEP user, you need to know how to start taking it, how to stop and how to restart it. You also need to know what to do if you realise you have missed a dose.

Some of the advice below is different depending on your sex and gender. This is because of biological differences and the impact of hormones taken by trans people, as well as gaps in the research. As more PrEP research has been done with men than women, more is known about how men can take PrEP.

Some recommendations apply to cisgender men who want to protect themselves during sex, including vaginal sex and anal sex. Cisgender men were assigned male at birth and still identify as male.

Other recommendations are for cisgender women, transgender women and transgender men. The same recommendations can be followed by people who want to protect themselves from HIV when injecting drugs.

Our advice on stopping and starting tenofovir disoproxil / emtricitabine PrEP is based on guidance from the World Health Organization.

Starting PrEP

If you are a cisgender man, you can start by taking two pills at once. This will give complete protection against HIV after two hours and for the following 24 hours.

If you are a cisgender woman, a transgender woman or a transgender man, or if you are injecting drugs, you need to take PrEP for a week for the medication to reach adequate levels in your bloodstream. Take one PrEP pill a day for seven days. However, if you are likely to have sex without a condom within the first seven days after starting PrEP, take two tablets at least two hours before having sex and then take PrEP every day.

Continuing PrEP

Once you’ve started, continue to take a single PrEP pill once a day, for as long as you need protection from HIV. The period of time you need protection might be quite short (just a few days) or much longer (several years). This advice is the same for everybody.

Take the pill at around the same time each day (give or take two hours). It may be easier to get into the habit of taking PrEP if you combine it with a daily routine. This could be brushing your teeth, having dinner or going to bed. Think about where you will keep your pills – somewhere you will see them at the right time, or kept out of the sight of other people? You could set an alarm on your phone or watch each day. Or you could get a pill box from a pharmacy – this makes it easy to see whether you have taken or missed a dose.

Stopping PrEP

It’s fine to take a break from PrEP if you won’t need protection from HIV for a while.

If you are a cisgender man, continue to take PrEP once a day for two days after the last time you had sex without a condom. For example, if you last had sex on Sunday, take PrEP on Monday and Tuesday, and then stop.

If you are a cisgender woman, a transgender woman or a transgender man, continue to take PrEP once a day for seven days after the last time you had sex without a condom. For example, if you last had sex without a condom on Sunday, take PrEP for another week, and then stop.

If you are using PrEP to protect yourself from HIV when injecting drugs, continue for seven days after the last time you shared injecting equipment.

Re-starting PrEP

To start PrEP again, whether after a few days, weeks or months, simply do what you did at the beginning. Follow the advice on starting PrEP given above.

Some cisgender men start and stop PrEP regularly around the days they have sex – for example, at weekends. This works best for men who usually know in advance when they will have sex. This is sometimes called event-based dosing, on-demand PrEP or 2-1-1 PrEP. If you start and stop PrEP as outlined on this page, you will be following the guidance for taking event-based PrEP.

Other people start and stop PrEP around longer periods of time when they need protection – for example, when travelling or when a sexual partner is visiting. If you are a cisgender woman, a transgender woman or a transgender man, you need to take PrEP for seven days before it fully protects you, and you need to continue to take it for seven days after your last possible exposure to HIV.

If you miss a dose

If you have already been taking PrEP consistently for at least a week, an occasional missed dose will not stop PrEP from working. If you are a cisgender man, you need to take at least four doses a week for PrEP to work. If you are a cisgender woman, a transgender woman or a transgender man, you need to take at least six doses a week.

• If you forget to take a dose, you can take it within 12 hours. If you remember later than 12 hours after the time you normally take PrEP, take the next dose at the normal time.

But if you have been taking PrEP for less than a week, or are using event-based dosing, there will be less medication in your body, so there is less flexibility. You should try to take all the recommended doses.

• If you forget to take a dose, take it as soon as you remember. If you took a dose before sex, but forgot to take another dose soon after sex, try to take a dose within 48 hours of sex.
• If you should have taken a double dose to start PrEP before you had sex, but forgot, take two pills as soon as you remember, even if this is after sex.
• You should also contact your clinic without delay to see if you should get extra protection with a 28-day course of post-exposure prophylaxis (PEP). This usually adds a third drug to the two drugs in PrEP. It’s best to start this within 24 hours, and definitely within 72 hours. There’s more information about PEP on another page.

If you have stopped taking PrEP and have had sex that could have exposed you to HIV, contact your clinic without delay to see if you should take a 28-day course of post-exposure prophylaxis (PEP). This usually adds a third drug to the two drugs in PrEP. It’s best to start this within 24 hours, and definitely within 72 hours. There’s more information about PEP on another page.

Checkups while taking PrEP

Regular checkups are important while taking PrEP.

You should have an HIV test every three months, to check that you remain HIV negative. You may be offered an extra test one month after starting PrEP, to check that you didn’t acquire HIV just before starting PrEP. It is best to be tested for HIV using a fourth-generation antibody-antigen test. These are more sensitive than rapid antibody tests and will detect HIV sooner. The majority of people who acquire HIV will receive a positive result using a fourth-generation HIV test within four weeks of exposure.

Rapid HIV tests which use a sample of moisture from the mouth do not always pick up recent infections, so should not be relied on while using PrEP. In some situations, you might be offered a viral load test: this is able to detect HIV before your body has produced antibodies against HIV, during the first weeks of infection. However, this test not available everywhere.

You may also have regular blood tests to check how PrEP is affecting your kidney function, especially if you are over 40 or 50 years old, or have slightly reduced kidney function. You may also have tests for other sexually transmitted infections at these clinic visits.

If you stop taking PrEP and subsequently have condomless sex more than a week later, it’s a good idea to get a fourth-generation antibody test before starting PrEP again.

If you are not taking PrEP and you have flu-like symptoms, possibly with a rash, within a month of condomless sex, this may be a symptom of HIV infection. You should have a fourth-generation HIV test a month after the most recent exposure and delay starting or re-starting PrEP until you have been confirmed HIV negative.

If you have just started PrEP and you have flu-like symptoms, possibly with a rash, this may be a symptom of HIV infection. Contact your clinic immediately to arrange a fourth-generation HIV test and/or viral load test. Your clinic may add a third drug to your PrEP in case you have HIV.

Telling your GP you are taking PrEP

It is a good idea to tell your general practitioner or primary care physician that you are taking PrEP containing tenofovir disoproxil and emtricitabine, to avoid interactions with other prescription medicines.

PrEP if you have hepatitis B

Tenofovir disoproxil, one of the drugs in PrEP, is also used to treat hepatitis B. You will be tested for hepatitis B before you start PrEP. If you have hepatitis B, you must take PrEP every day – you should not start and stop PrEP just for the times you need protection.

If you want to take a break from PrEP, you should discuss with your clinic how to safely stop taking it. Stopping tenofovir disoproxil suddenly when you have hepatitis B could lead to a flare-up of hepatitis.

Using PrEP during pregnancy, breastfeeding or when you are trying to conceive

PrEP is safe to take during pregnancy and breastfeeding. You can take it when you are trying to conceive and it will not affect your chances of becoming pregnant.

Who shouldn’t take PrEP?

• People living with HIV
• People with reduced kidney function (your kidney function should be tested before starting PrEP). One of the other types of PrEP may be more suitable for you.
• Adolescents weighing less than 35kg (five and a half stone).

Side effects

The most common side effects of PrEP containing tenofovir disoproxil and emtricitabine (affecting at least one in ten people) are:

• Feeling sick or being sick
• Diarrhoea
• Rash
• Headache
• Feeling weak

Other common side effects (affecting at least one in a hundred people):

• Stomach pain, indigestion, flatulence

• Feeling dizzy or weak
• Difficulty sleeping, abnormal dreams
• Rashes (including red spots or blotches sometimes with blistering and swelling of the skin), which may be allergic reactions, itching, changes in skin colour including darkening of the skin in patches
• Other allergic reactions, such as wheezing, swelling or feeling light-headed

Side effects are most likely to occur during the first month you are taking PrEP.

Taking PrEP with food or just after a meal may limit any side effects. If you are a cisgender man, the first dose of two PrEP pills may cause more side effects than the usual dose of one pill, so it’s a good idea to take the double dose with food. If this still causes you trouble, you could try taking the two pills a few hours apart.

If you have side effects which don’t go away or get worse, speak to staff at your clinic.

Uncommon or rare side effects

Taking tenofovir disoproxil may lead to increased creatinine levels in fewer than one in a hundred people. High creatinine levels can be a sign of abnormal kidney function. Your blood can be tested regularly (for example, once a year) to check your kidney function and creatinine levels. If you have weakened kidney function, the alternative PrEP pill of tenofovir alafenamide / emtricitabine (Descovy) may be more suitable for you.

Tenofovir disoproxil slightly reduces bone mass, typically by around 1% - 2% in the first year. As adolescence is an important period for bone growth, the alternative PrEP pill of tenofovir alafenamide / emtricitabine (Descovy) is more suitable during adolescence.This form of PrEP may also be more suitable for older people with a higher risk of bone fractures.

In adults, the kidneys and bones usually return to normal after stopping taking PrEP.

There’s more information about side effects on another page.

Interactions with other medicines

When two drugs are taken at the same time, their interaction can affect the drugs’ effectiveness and side effects.

PrEP containing tenofovir disoproxil and emtricitabine can interact with high doses of non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen or diclofenac – these medications are taken for pain or inflammation. Discuss with your doctor whether it is safe to take both PrEP and NSAIDS.

PrEP does not interact with:

• Alcohol or recreational drugs
• Hormonal contraception
• Gender-affirming hormone therapy
• Erectile dysfunction drugs
• Anabolic steroids

Tell your clinic if you use protein or creatine powders. These can impact the results of blood tests that check your kidney health.

The University of Liverpool provides an online tool to check for interactions between anti-HIV drugs (including PrEP) and other medications. You enter the names of your PrEP drugs (tenofovir disoproxil and emtricitabine) in the left column, and the other medications you are taking in the next column. The results are provided with a traffic-light system: if the result is red or amber, it’s worth checking with your doctor or pharmacist. If it’s green, there shouldn’t be any problem. Visit www.hiv-druginteractions.org/checker or download the Liverpool HIV iChart app for iPhone or Android.

Drug resistance

Some people worry that while taking PrEP they may get drug resistant HIV. It’s important to remember that HIV drug resistance can only happen if you take PrEP when you already have HIV. This is why you should get tested for HIV before you start PrEP, and keep testing regularly.

If you continue taking PrEP or start taking PrEP again after you acquire HIV, this could drive HIV to develop resistance to the drugs you are taking as PrEP. This would restrict your options for treating HIV.

But if you don’t have HIV and you take PrEP as directed, you almost certainly won’t catch HIV and you won’t develop drug resistance.

There is another way in which resistance can affect PrEP. There are a very small number of people who have acquired HIV when taking PrEP despite having adequate drug levels in their blood. In almost all cases, they acquired a form of HIV that had resistance to one of the drugs in PrEP. Resistance to both drugs in PrEP is highly unusual.

There’s more information about resistance on another page.

Does PrEP prevent STIs?

PrEP does not prevent other sexually transmitted infections so it’s a good idea to have regular tests for sexually transmitted infections while you are taking PrEP.