What is PEP?

PEP is short for Post-Exposure Prophylaxis. It’s where you take an antibiotic after condomless sex (post-exposure) to prevent STIs (prophylaxis). PEP for bacterial STIs can be taken after condomless sex to help prevent syphilis and chlamydia. It is less effective against gonorrhea. ‍

PEP does not prevent or treat HIV. If you are taking PEP, you need to also keep taking HIV PrEP or HIV treatment.

How do I take PEP?

For PEP to be the most effective, it needs to be taken every time you have condomless sex.

Who is PEP for for?

PEP is for men who have sex with men, trans women and other gender-diverse people who were born with a penis. This is because the research supporting PEP for bacterial STIs (more on that below) showed it was effective in people with these body types.

Unfortunately, research suggests PEP for bacterial STIs is not as effective for people who were born with vaginas. This includes cis women, trans men and other gender-diverse people with this body type. At this time, PEP for bacterial STIs is not recommended for these people – however, you can speak to your clinician to decide what might be best for you.

PEP effectiveness

The original evidence for PEP for bacterial STIs came from three studies that followed men who have sex with men and transgender women. These studies took place in France and the USA and included people with and without HIV. In these trials, PEP reduced the risk of chlamydia by 70-89%. It also reduced the risk of syphilis by 73-87%.

PEP and Gonorrhea

In two of the studies, PEP for bacterial STIs appeared to reduce the risk of gonorrhea by 51-57%. In one study, PEP did not reduce the risk of gonorrhea. At first, these mixed signals appeared to indicate it was effective.

However, new research in 2025 has now confirmed that the effectiveness of PEP against gonorrhea is much lower than other bacterial STIs. It does not provide substantial protection against them. This research has confirmed the effectiveness of PEP against chlamydia and syphilis.

Is PEP safe?

It is a widely-used antibiotic with a low risk of side effects and drug interactions. It’s often used to prevent malaria and treat acne, where it can be safely taken for days or weeks at a time. It’s also used to treat some common infections.

It can also make you more sensitive to sunlight, so it’s important to wear sunscreen for at least 24 hours after you’ve taken it. If you’re having a horny beach vacation, be careful! Don’t forget to take shade breaks and re-apply.

Make sure you don’t lie down for 30 minutes afterwards.

This is because they can interfere with how the medication is absorbed, making it less effective.

Some researchers have cautioned that using the antibiotic for PEP may increase the risk of antibiotic resistance, particularly when used inconsistently. Public health units are carefully considering these risks alongside the benefits of reducing STI transmission. At the time of writing, PEP has been formally endorsed by America's Centers for Disease Control and Prevention. The Public Health Agency of Canada is currently conducting its review.

Drug interactions

The antibiotic is known to interact with some oral retinoids, which are medications used for acne and psoriasis. Using these medications with the antibiotic can raise the risk of a rare condition involving increased pressure in the brain.

For this reason, you should not use PEP if you take these medications. You should also never share your medication with others.

Can I take PrEP and PEP?

Yes! In fact, we recommend taking them both. If you are a good candidate for PrEP you will also be a good candidate for PEP. It's important to discuss the combined use of these medications with your healthcare provider, as both have potential risks and require regular monitoring.

PrEP and PEP are separate prevention approaches. PEP does not prevent HIV, so you need to keep taking your PrEP alongside it. With PrEP and PEP together, you can boost your protection to help prevent HIV and three major STIs. Yay, science!

How to talk to a clinician

You should be able to talk to a clinician from sexual health clinics that serve LGBTQ2S+ people. You can also get it from family doctors. However, access can vary depending on where you live – PEP is new, and not all clinics are informed. 

Freddie can help you talk to a clinician online! We can connect new and existing patients with PEP if they’re eligible. Ask your clinician for more information.

Not a patient yet? Get started with Freddie today! Please note, Freddie only provides PEP alongside PrEP. If you are a good candidate for PEP for bacterial STIs, you are also a good candidate for PrEP!

Because both treatments are a part of sexual healthcare, it's best to get them from the same provider. That way we can monitor your health the most effectively. If you are getting PrEP from another provider but are looking for PEP with Freddie, you will need to switch your PrEP care to us. Switching to Freddie for PrEP is easy – just ask your clinician.