PrEP (HIV Pre-exposure Prophylaxis) is a medicine for HIV negative people. It can reduce the risk of catching HIV when taken as instructed. PrEP is made up of two drugs, tenofovir and emtricitabine. Both these drugs have been widely used for many years to treat HIV. The drug has been used by several thousands of HIV negative people to reduce the risk of HIV. It does not prevent other STIs.

What happens during my first visit?

During your first visit your risk will be assessed and you will be offered tests including:

  • HIV blood test
  • Confirmation of your Hepatitis B status
  • Blood and urine tests to check your kidney function
  • STI and Hepatitis C screen
  • Pregnancy test (if required)

PrEP may not be suitable for you if you have any illness that could be due to HIV, if you are taking other medication which may interact with PrEP or if you have active hepatitis B.

Some people take PrEP daily and some take it less frequently (event-based dosing). Your clinician will help you to make this decision and ensure you have the information you need to make the right choice for you.

If PrEP is suitable for you, we will be able to prescribe up to 3 months’ supply.

If you are starting PrEP for the first time, the clinic will contact you within the first 4 weeks to see how you are getting on with the tablets.

How often will I need to come to clinic?

During the time you are taking PrEP you will need to visit the clinic every 3 months for an HIV test and sexual health check. You may also need to have a blood test to check your kidney function. If you are still eligible to receive PrEP we can prescribe you up to a further 3 months’ supply of tablets at each visit. If you have any concerns between visits about PrEP or your sexual health, you are welcome to contact the clinic earlier.

What if my circumstances change?

Your circumstances and risk of catching HIV may change. If you are no longer at a high risk of HIV there is no benefit from PrEP. If your risk increases you may be prescribed PrEP again to help to reduce that risk.

What if I need to go to a different clinic?

If you need to go a different sexual health clinic for any reason you should let the staff at the new clinic know that you are taking PrEP.

What are the possible risks and side effects?

The possible side-effects of PrEP will be explained by the clinic staff and are also provided in the information leaflet that comes with the medicine. It is important to take PrEP as prescribed, without missing doses. You can also reduce your risk of acquiring HIV and other STIs by using condoms.

Most people taking PrEP do not report side effects. However, like all other medicines, PrEP can cause side effects. In studies of PrEP, fewer than 1 in 10 people reported mild nausea, diarrhoea, bloating and headache in the first month of treatment.

PrEP can also affect your kidneys which is why monitoring is important. In studies a small proportion of people taking PrEP developed reduced kidney function, but these changes reversed on stopping PrEP. The risk is higher if you are older than 40 or if you already have reduced kidney function when you start PrEP.

PrEP can also reduce bone density (how much calcium and other minerals are in your bones) by 1-5%, causing slight thinning of the bones. This loss reverses after PrEP is stopped. This side effect is more important if you already have low bone density related to other factors. It might also be important if you are younger than 30 as your bones are still developing. So far there have not been any reports of bone fractures related to PrEP use.

Event based PrEP might reduce the risk of those side effects, though this has not been formally studied yet.

If you experience any unpleasant side effects, you should discuss these with the clinic staff. You may need to interrupt or even stop PrEP.

How do I take PrEP?

Taking PrEP as a DAILY dose

Daily PrEP can be used for anal and vaginal/front sex.

  • If you are just about to start daily dosing but think you might have a risk within the next few days, start with a double dose.
  • For anal sex, four or more daily doses each week will give good protection, especially after the first week. But four doses a week does not leave room for any missed doses.
  • For vaginal or front sex you need to take PrEP at least six days a week.

Taking PrEP ON DEMAND (event-based dosing)

Using PrEP before and after sex is very effective when used correctly. It is not suitable for everyone and should only be used for anal sex and by men who are having vaginal sex.

On-demand dosing involves:

  • Taking a double dose of PrEP (two pills) between 2 and 24 hours before sex
  • Taking a single pill 24 hours after the double dose.
  • Taking another single pill the following day, 24 hours later.

If you have sex once using on-demand dosing you will need to take four pills.

What should I do if I miss a pill?

If you use daily dosing and miss one or even two pills you should still be covered. If you miss more than this, please contact clinic.

If you use daily dosing and miss more than a week of pills you will need to restart with either seven days of daily dosing or a double dose to get full protection.

If you have any risks when you are not taking PrEP it is important to have another HIV test before restarting it.

If you are using PrEP on-demand and have missed doses you should contact clinic as soon as possible in case PEP is necessary.

How do I stop PrEP?

If your circumstances change you may decide not to keep taking PrEP.

You should continue daily for seven days if you are protecting your vagina/front.

Continue for two more daily doses if you are protecting your bottom or penis.

If your circumstances change again, it is easy to restart PrEP.

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Further questions

You can ask the clinic staff any other questions you may have about taking PrEP.