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Doxy-PEP (Doxycycline Post -Exposure Prophylaxis)

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The main points

Doxy-PEP (Doxycycline Post-exposure prophylaxis) is an oral dose of an antibiotic called doxycycline that is taken within 72 hours (3 days) of having sex (oral, anal, or vaginal) to protect against syphilis and chlamydia.

What is Doxy-PEP (Doxycycline Post-Exposure Prophylaxis)?

Doxy-PEP (Doxycycline Post-exposure prophylaxis) is an oral dose of an antibiotic called doxycycline that is taken within 72 hours (3 days) of having sex (oral, anal, or vaginal) to protect against syphilis and chlamydia.

Doxycycline is a common antibiotic used to treat certain infections, control acne, and prevent malaria. It does not work against viral infections such as HIV or herpes. In clinical trials of STI prevention for gay, bisexual and men who have sex with men, Doxy-PEP decreased syphilis (70-80%) and chlamydia (80-90%) transmission. For gonorrhoea, it was less effective (some studies found no effect while other studies found a decrease of 50 -55%).

Doxy-PEP is different to HIV PrEP (Pre-exposure prophylaxis) or HIV PEP (post-exposure prophylaxis). Doxy- PEP and HIV PrEP can be used together for sexual health protection.

How does Doxy-PEP work?

To use Doxy-PEP, you take 200 mg of doxycycline (usually two tablets) up to 72 hours after sex to reduce your risk of bacterial STIs. So, if you have multiple encounters over the weekend, a single dose of Doxy-PEP is sufficient to help prevent transmission.

Here’s a visual example of how it works

Shv Doxy Illustration
​How does Doxy-PEP work

As Doxy-PEP is not 100% effective for all STIs, regular STI testing is still recommended when taking it.

Who can benefit most from Doxy-PEP?

Doxy-PEP is most likely to benefit people at higher risk of syphilis, such as gay, bisexual, and other men who have sex with men (GBMSM), and transgender women, especially with recent syphilis or multiple recent STIs. GBMSM who have cisgender female partners or partners with a uterus may also benefit as it decreases transmission of chlamydia and syphilis to these partners who can have poor health outcomes (pelvic inflammatory disease, subfertility and congenital syphilis if pregnant).

What is the risk of taking Doxy-PEP: Antimicrobial resistance

Doxy-PEP can lower the risk of bacterial STIs but as it is an antibiotic it may also impact on other bacteria. For example, it might change the balance of good bacteria in your body (called the microbiome), and using antibiotics more often can lead to antibiotic resistance — which means some infections may become harder to treat. This can have serious consequences for infections in individuals but also the broader community if certain infections become resistant. If you have concerns about antimicrobial resistance and decided not to take Doxy-PEP, an alternative way to manage your risk is through frequent STI testing.

Are there any side effects of taking Doxy-PEP? :

  • Common but non-serious side effects include nausea, vomiting and diarrhoea.
  • Your skin may become more sensitive to sunlight, causing a rash or sunburn.
  • Rare but serious reactions like allergies, oesophageal ulcers or liver damage.

Where can I get Doxy-PEP?

Doxy-PEP can be accessed through a sexual health or general practice clinic with a doctor, nurse practitioner or other health professional who can prescribe medication. Your healthcare provider can help you decide if Doxy-PEP is right for you. Together, you’ll consider your health, your sexual activity, and what other STI prevention methods you already use.

How long can I take Doxy-PEP?

Doxy-PEP is usually recommended for up to 6 months, followed by a review with your healthcare provider to reassess your ongoing needs.

Will Doxy-PEP affect my pregnancy or breastfeeding?

  • Do not take doxycycline after the 18th week of pregnancy, as after this time, doxycycline can cause bone and dental changes in the developing baby.
  • Discuss the risks and benefits of taking doxycycline while breastfeeding with your health professional. Short courses (7-10 days) are considered safe.
  • Other STI prevention strategies should be considered.

What are some other ways I can lower my risk of getting sexually transmissible infections (STIs) and blood borne viruses (BBVs)?

As Doxy-PEP is not 100% effective for all STIs, regular STI testing is still recommended when taking it.

You can lower your risk of getting STIs and BBVs by using barrier protection (external condoms, internal condoms or dental dams), correctly during any type of sex (vaginal, anal or oral sex) and when sharing sex toys.

Barrier protection is not 100% effective at preventing STIs and BBVs.

You can also lower your risk of getting a BBV by:

If your sexual partner/s and/or injecting equipment sharing partner/s are living with HIV, you can talk to them about treatment as prevention (TASP). This means taking antiretroviral tablets to prevent passing on HIV. For more information, you can talk to your doctor or nurse.

You can also lower your risk of getting an STI or BBV by both you and your sexual partner/s and/or injecting equipment sharing partner/s having regular STI and BBV testing. For more information on testing at Sexual Health Victoria, see our clinics, or you can book an appointment online.

Where to get more information and support

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