Antibiotic PEP against bacterial STIs
DoxyPEP refers to post exposure prophylaxis against bacterial sexually transmitted infections (STIs). It involves taking the antibiotic doxycycline after sexual intercourse to reduce the risk of certain bacterial STIs.
Notice
Taking doxycycline entails risks for individual health and public health. We recommend taking doxycycline only with medical supervision and in combination with regular STI testing.
Important: using DoxyPEP may influence STI diagnosis and treatment.
What is DoxyPEP?
DoxyPEP consists of taking the antibiotic doxycycline after sexual intercourse to prevent infection with syphilis or chlamydia.
Studies have shown effectiveness with a single dose of 200 mg of doxycycline, ideally within 24 hours and at the latest within 72 hours after sexual contact. A dose of 200 mg must never be exceeded within a 24‑hour period.
Doxycycline is the only antibiotic for which effectiveness as post‑exposure prophylaxis against bacterial STIs has been demonstrated. This antibiotic is also used to treat other infections.
Proven effectiveness
Syphilis and chlamydia
DoxyPEP can prevent syphilis and chlamydia infections when the bacteria are not resistant to doxycycline. Protection is not complete and infection remains possible. Regular testing therefore remains essential.
Taking doxycycline may prolong the diagnostic window.
Gonorrhoea
DoxyPEP provides little protection against gonorrhoea and many other bacterial STIs that are already largely resistant to this antibiotic.
HIV and viral STIs
DoxyPEP has no effect against HIV or against viral infections transmitted during sexual contact, such as hepatitis A/B, herpes, HPV or Mpox.
Populations studied
The effectiveness of DoxyPEP has been demonstrated in cisgender men, transgender women and other people assigned male at birth.
To date, no effectiveness has been demonstrated in cisgender women, transgender men and other people assigned female at birth.
Do I need DoxyPEP?
DoxyPEP may be relevant for men and trans people if the following situations apply:
- sexual contacts with men with frequently changing partners
- diagnosis of a bacterial STI within the last 12 months
- regular sexual activity under the influence of psychoactive substances (e.g. chemsex)
During a consultation with a healthcare professional, it is possible to assess together whether DoxyPEP is appropriate.
What are the benefits of DoxyPEP?
Taking DoxyPEP can reduce the risk of acquiring syphilis or chlamydia.
Risks and side effects
HIV treatments
There are no interactions between preventive (PrEP) or therapeutic HIV treatments and doxycycline.
Alcohol and substances
Taking doxycycline together with alcohol or psychoactive substances can reduce its effectiveness and increase side effects.
Light sensitivity
Doxycycline significantly increases sensitivity to sunlight (photosensitivity). UV protection is essential and sun exposure should be avoided.
Systemic effects
Antibiotics can affect the immune system, cause allergic reactions and disrupt the balance of the gut microbiota.
Resistance
Regular use of antibiotics promotes the development of resistance, which can also affect STIs. Regular testing therefore remains essential.
In general, antibiotic use should be limited to situations in which the expected benefits outweigh the risks.
When and how to take DoxyPEP
DoxyPEP consists of a single dose of 200 mg of doxycycline (1 or 2 tablets depending on the strength indicated on the package), preferably within 24 hours and no later than 72 hours after sexual contact.
A dose of 200 mg within 24 hours must not be exceeded, which means the dose should not be repeated within a 24‑hour interval.
It is recommended to take doxycycline with sufficient fluids. Taking it with food can improve tolerability.
Use over a prolonged period
If the risk of infection persists, the dose may be repeated after 72 hours.
Where to obtain DoxyPEP
Doxycycline is available by prescription in all pharmacies.
For medicines ordered online from abroad, there is no guarantee regarding the active ingredient, dosage or the presence of other potentially harmful substances.
We recommend using DoxyPEP within the framework of medical follow‑up. At a sexual health centre, a physician can provide personalised counselling, issue a prescription and plan follow‑up testing.
Impact on STI testing and treatment
If DoxyPEP has been used recently, it is important to report this at the next appointment so that STI testing and treatment can be adapted accordingly.
How much does DoxyPEP cost?
Doxycycline is a commonly used antibiotic. Generic versions are available in Switzerland at an affordable price: approximately CHF 15 for 10 tablets.
Doxycycline is available in different strengths (100 mg or 200 mg per tablet). This must be taken into account when using it.
Health insurance
Doxycycline is not approved in Switzerland for the prevention of STIs. DoxyPEP is therefore prescribed off label, and the costs must be covered by the users themselves.