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Find the nearest to meDoxy-PEP (Doxycycline Post-Exposure Prophylaxis)
We are planning to offer doxy-PEP to some people at higher risk of syphilis, following an assessment and discussion in clinic.
What is doxy-PEP?
Doxy-PEP is doxycycline (an antibiotic) taken after sex to reduce the chance of catching some bacterial STIs, particularly syphilis and chlamydia. It is not 100% effective, and in the UK it is unlikely to protect well against gonorrhoea, so regular testing remains essential.
Doxy-PEP does not protect against viral infections such as HIV, hepatitis B, or mpox.
Who may be offered doxy-PEP?
Doxy-PEP may be offered to cisgender gay, bisexual and other men who have sex with men (GBMSM) and trans women who have sex with men who are at higher risk of syphilis.
This may include people who, for example:
- Have had syphilis or another bacterial STI in the last 12 months, and/or
- Have multiple or new partners, condomless sex, group sex, or chemsex.
- In some circumstances, other people at high risk of syphilis may be offered doxy-PEP case-by-case after discussion in clinic.
How to take doxy-PEP
- Take 200 mg doxycycline (two 100 mg capsules/tablets) as soon as possible after sex, ideally within 24 hours, and no later than 72 hours.
- Do not take more than 200 mg in any 24-hour period.
- If you have sex again, wait at least 24 hours before taking another dose.
- If you have sex repeatedly over a short period, you may prefer to take a single 200 mg dose at the end of that 72-hour period rather than multiple doses (discuss what’s best for you with the clinic).
How to reduce side effects and help it work properly
- Take with a full glass of water and some food.
- Do not lie down for 30 minutes after taking it (to reduce irritation/reflux).
- Keep a 2-hour gap before/after taking: antacids, indigestion remedies, and supplements containing iron, zinc, calcium or magnesium (these can reduce absorption).
Side effects
Most people tolerate doxycycline well. Possible side effects include:
- Nausea, vomiting, diarrhoea, stomach upset
- Reflux / irritation of the gullet (oesophagus)
- Headache
- Skin sensitivity to sunlight (photosensitivity)
- Thrush (occasionally)
Sun advice: use high-factor sunscreen in sunny weather and avoid sunbeds.
Get urgent medical advice if you develop:
- Signs of an allergic reaction (e.g., facial swelling, wheeze, breathing difficulty)
- A severe rash or blistering skin
- Severe swallowing pain or chest pain after taking the tablet
- Severe headache or visual disturbance
Interactions and important cautions
Please tell us about all medications you take (including over-the-counter and supplements). Doxycycline may interact with some medicines, including:
- Warfarin (may require INR monitoring)
- Some anti-seizure medicines (e.g., carbamazepine, phenytoin)
- Isotretinoin (used for acne)
- Some immunosuppressant medicines (e.g., ciclosporin)
If you need antibiotics for another reason (e.g., a chest infection), tell the prescriber you are using doxy-PEP.
Alcohol: regular heavy drinking may reduce the effectiveness of doxycycline and can increase side effects.
Pregnancy and breastfeeding
If you are pregnant, trying to conceive, or breastfeeding, please discuss with the clinic before taking doxy-PEP.
Testing and prevention
Doxy-PEP is only one part of STI prevention. If you are using doxy-PEP, we recommend:
- Regular STI testing every 3 months (and sooner if you have symptoms)
- Considering HIV PrEP if you are at risk of HIV
- Keeping vaccinations up to date where appropriate (e.g., hepatitis A/B, HPV, mpox)
- Using condoms if/when this works for you
Antibiotic resistance (AMR)
Antibiotic resistance is an important public health issue. Using doxy-PEP can increase antibiotic exposure, so we offer it targeted to people at highest risk and review ongoing need regularly. We also monitor infections and testing results to help ensure doxy-PEP is used as safely and effectively as possible.
How to get DoxyPEP
If you have questions about doxy-PEP or think it may be right for you, please speak to the SWISH team.
You can discuss more during your appointment in SWISH and see if eligible
or go to the following links for more information
Doxycycline: antibiotic for bacterial infections - NHS
Download DoxyPEP 'Little Back Pocket Guide'
