DoxyPEP is an antibiotic that is taken within 72 hours of sex to reduce the chance of getting bacterial STIs, particularly syphilis and chlamydia. It is known as post-exposure prophylaxis (PEP) and contains the active ingredient doxycycline.

DoxyPEP is recommended for people who are at the highest risk of bacterial STIs, including gay and bisexual men and trans women. It should be used alongside regular STI testing and condom use for the most effective STI protection.

DoxyPEP contains 200mg of doxycycline, an antibiotic that works by killing or preventing bacteria from multiplying. It binds to chlamydia- or syphilis-causing bacteria to stop them from producing the proteins they need to survive and multiply in the body and cause infection.

DoxyPEP does not protect against viral STIs, like HIV or herpes. See our pre-exposure prophylaxis (PrEP) treatment page for more information on HIV protection tablets.

How long does DoxyPEP take to work?

DoxyPEP should be taken within 72 hours of unprotected sex, but ideally within 24 hours. That’s because the active ingredient, doxycycline, takes 24 to 48 hours to start working.

How effective is DoxyPEP?

Research shows that DoxyPEP reduced the risk of bacterial STIs in different populations by 46%. A UK guideline published by the British Association for Sexual Health and HIV found that DoxyPEP lowers the risk of:

• chlamydia by 79%
• syphilis by 80%

DoxyPEP is less effective at reducing the risk of gonorrhoea because most UK gonorrhoea infections are resistant to doxycycline. The risk of gonorrhoea is only reduced by around 50%.

DoxyPEP involves taking 200mg of doxycycline within 72 hours of having unprotected sex. You will usually be prescribed 100mg doxycycline tablets. You should take two 100mg pills at the same time, swallowing them whole with water.

After you have taken doxycycline, you should avoid lying down for at least 30 minutes to reduce irritation of your throat and food pipe (oesophagus).

When to take DoxyPEP

Ideally, you should take DoxyPEP within 24 hours of condomless sex, but no more than 72 hours later.

How much DoxyPEP to take

The DoxyPEP dose is 200mg of doxycycline, which is usually given as two 100mg tablets.

How long do you need to take DoxyPEP for?

DoxyPEP is taken once within 72 hours of having condomless sex. If you have sex again within 24 hours of taking doxycycline, you should take another dose 24 hours after your last dose. DoxyPEP can safely be taken every day when having condomless sex.

What if I take too much DoxyPEP?

If you take more doxycycline than you should, contact your doctor, or in an emergency, go to your nearest A&E for medical attention.

What should I do if I take DoxyPEP too late?

If it has been more than 72 hours since you had condomless sex, you should not take DoxyPEP as it is unlikely to be effective. Instead, you should consider taking an STI test or contact your GP or sexual health clinic for more advice.

Make sure to wait around 2 weeks to test for chlamydia and gonorrhoea, or it may be too early to show up on a test. Syphilis can take 3 to 6 weeks to show on a test.

You will need a prescription from a doctor to get DoxyPEP either privately, via a sexual health clinic or an online doctor service, or on the NHS.

Can I buy DoxyPEP online?

Yes, you can request DoxyPEP from Superdrug Online Doctor by:

1. Completing an online health questionnaire for one of our doctors to review.
2. Select your preferred treatment and make a payment.
3. Once approved, we will dispatch your medication in discreet packaging for next-day delivery.
4. If your request is not approved, a doctor will message you via your patient account with advice about what to do next.

Can I buy DoxyPEP over the counter?

No, DoxyPEP is not available to buy over the counter because you need a prescription from a doctor first.

Can I get DoxyPEP on the NHS?

Yes, DoxyPEP is available on the NHS in some regions. You will need to make an appointment or visit a sexual health clinic to find out if it is available in your area and if it is suitable for you.

DoxyPEP can cause side effects, although not everyone will get them.

Common side effects (may affect up to 1 in 10 people) are:

• feeling or being sick (nausea or vomiting)
• headaches
• mild stomach issues, such as acid reflux or upset stomach
• inflammation of the heart
• worsening of systemic lupus erythematosus (SLE)

Uncommon side effects (may affect up to 1 in 100 people) are:

• heartburn
• vaginal infection

Rare side effects (may affect up to 1 in 1,000 people) include:

• anxiety
• difficulty swallowing
• sore or painful tongue
• red skin
• severe headache with vision changes
• liver inflammation and damage
• yellowing of the skin and eyes (jaundice)
• inflammation of the pancreas
• upset stomach, loss of appetite, diarrhoea, stomach pain
• darker patches on the skin
• ringing or buzzing in the ear

A full list of side effects can be found in the patient information leaflet that comes with your medication.

How long do DoxyPEP side effects last?

Because DoxyPEP is taken on demand rather than every day, the side effects may only last a short time. If they last for longer than a few days or are difficult to manage, speak to your doctor for advice.

What to do if you get DoxyPEP side effects

Most DoxyPEP side effects are mild and can be managed at home. You can try the following for side effects, such as:

• headaches – take over-the-counter painkillers, like paracetamol and ibuprofen, and drink plenty of water
• feeling or being sick – stay rested until you feel better, drink plenty of clear fluids, and eat plain foods
• heartburn – speak to a pharmacist about taking antacids and avoid spicy foods and caffeine, which can be triggers

DoxyPEP is not for everyone and is primarily for people who are at the highest risk of getting a bacterial STI. DoxyPEP is available if you are:

• over 18
• a gay, bisexual, or trans man or any other man who has sex with other men
• a trans woman who has sex with men or cisgender women
• a sex worker
• at an increased risk of syphilis
• living with HIV
• at an increased risk of STIs because you have group sex, sex while on drugs, multiple sexual partners, or have occasional one-off partners

Do not take DoxyPEP if you are:

• under 18
• allergic to doxycycline or any other tetracycline antibiotics
• pregnant or trying to get pregnant
• breastfeeding

Before taking DoxyPEP, tell your doctor if you:

• are going to be exposed to strong sunlight or UV light
• have kidney or liver problems
• have myasthenia gravis (a disease that causes unusual tiredness and weakness of certain muscles)
• have porphyria
• have or have ever had systemic lupus erythematosus (SLE)
• think you have syphilis
• have diarrhoea or get diarrhoea when you take antibiotics
• are taking oral retinoids
• have oesophagitis

Doxycycline and other medications

Before taking DoxyPEP, tell your doctor if you are taking any other prescribed, over-the-counter, or herbal medications.

Do not take doxycycline if you:

• are taking penicillin
• have the anaesthetic methoxyflurane

The following medications can make DoxyPEP less effective:

• anatacids
• iron preparations
• oral zinc
• bismuth
• carbamazepine
• phenytoin
• barbiturates

Doxycycline can also impact the effectiveness of other medications, including:

• those used to protect against blood clotting
• oral contraceptives
• antacids containing calcium, aluminium, or magnesium
• bismuth salts
• iron preparations
• carbamazepine, phenytoin, or any barbiturates
• ciclosporin

There are limited alternatives to DoxyPEP, and at present, DoxyPEP is the current standard for preventing chlamydia and syphilis within 72 hours of unprotected sex.

Some of the other ways you can protect yourself against STIs include:

• using condoms each time you have sex
• taking regular STI tests (every 3 months)
• speaking to your doctor or a sexual health clinic about HIV pre- and post-exposure prophylaxis (PrEP) treatments
• getting prompt treatment if you test positive for an STI

At Superdrug Online Doctor, we can provide PrEP and offer a range of at-home STI test kits.

Is DoxyPEP the same as doxycycline?

Yes, DoxyPEP and doxycycline are the same thing. Doxy means doxycycline, while PEP stands for post-exposure prophylaxis.

DoxyPEP Vs doxycycline

DoxyPEP and doxycycline contain the same active ingredient, doxycycline, but DoxyPEP is a prevention strategy that is taken within 72 hours of unprotected sex to reduce the chance of getting syphilis and chlamydia.

Doxycycline, on the other hand, is the medication used as DoxyPEP, but it is also given as a course of antibiotics to treat a range of bacterial infections.

DoxyPEP vs azithromycin

DoxyPEP is a type of post-exposure prophylaxis that’s taken by people who are at an increased risk of STIs, like chlamydia and syphilis. It is an on-demand 200mg dose of doxycycline, an antibiotic, that should be taken within 72 hours of unprotected sex.

Azithromycin is another antibiotic used to treat various bacterial infections, including some STIs. Azithromycin is not available for STI prevention.

Can DoxyPEP be used for syphilis?

Yes, DoxyPEP is effective at preventing syphilis. Research shows that DoxyPEP can reduce the risk of syphilis by 80%.

Can DoxyPEP be used for gonorrhoea?

DoxyPEP is primarily used to prevent chlamydia and syphilis, but it does have some effect in preventing gonorrhoea. DoxyPEP can only reduce the risk of gonorrhoea by around 50%. As it is less effective, it is not used specifically for gonorrhoea prevention alone. It is less effective because most gonorrhoea infections in the UK are resistant to doxycycline, the antibiotic used in DoxyPEP.

How quickly do you need to take DoxyPEP after sex?

For maximum effectiveness, it is recommended that you take DoxyPEP within 24 hours of condomless sex. If this is not possible, it should be taken within 72 hours.

How often can you take DoxyPEP?

You should only take 1 DoxyPEP dose (200mg) in 24 hours. If you have sex within 24 hours of taking doxycycline, you should take another dose 24 hours after the last dose. You can take doxycycline every day when you are having condomless sex.

If you have sex more than once in 72 hours, you can take a single 200mg dose of doxycycline at the end of the 72 hours, rather than multiple doses to cover the entire period.

Can DoxyPEP be taken alongside PrEP?

Yes, you can take DoxyPEP alongside PrEP because they work differently. DoxyPEP is a post-exposure prophylaxis that is taken to prevent bacterial STIs, like syphilis and chlamydia, after having condomless sex. PrEP is a pre-exposure prophylaxis, which is taken before sex to prevent HIV.