Doxycycline post-exposure prophylaxis (Doxy-PEP) is attracting attention as a new method to help lower syphilis and other STIs among gay, bisexual, and other men who have sex with men (GBMSM) in Australia. As STI rates continue to climb, interest is increasing in approaches that go beyond just testing and treatment. Doxy-PEP might provide an extra option to help prevent infection, particularly for those at greater risk of getting syphilis and chlamydia.
Doxy-PEP involves taking two 100 mg doxycycline tablets within 48 to 72 hours of sex. Research shows it can significantly reduce the risk of syphilis and chlamydia significantly. Doxy-PEP may also reduce gonorrhoea in some cases, although results are varied. A single dose can offer some protection for a short period, such as a weekend with multiple partners.
In March 2023, a national roundtable led by ASHM released a Consensus Statement on Doxy-PEP use. It documented reductions of 70-80% in syphilis and 70-90% in chlamydia. The impact on gonorrhoea was more varied, with some studies showing no effect and others indicating reductions of around 50%. These findings are especially relevant for people with a recent history of syphilis or multiple STIs.
As with any antibiotic use, Doxy-PEP raises questions about antimicrobial resistance (AMR). Resistance occurs when bacteria adapt and become more difficult to treat. AMR is already a major concern in the treatment of gonorrhoea. While there is no immediate alarm around doxycycline resistance in syphilis or chlamydia, careful monitoring is essential. Using Doxy-PEP only when clinically recommended and with support from your doctor or clinician helps minimise risks. Individuals should not self-prescribe or use leftover antibiotics, as improper use can lead to increased antibiotic resistance.
ASHM’s Consensus Statement and recent patient guidance produce by ASHM indicates that Doxy-PEP is most appropriate for a specific groups of people. This includes gay and bisexual men (GBMSM), trans women and non-binary people assigned male at birth who have recently been diagnosed with syphilis, have two or more other STIs, or expect a period of increased sexual activity, such as during travel or sex events. In practice, this means that most GBMSM would not be eligible. The aim is to offer Doxy-PEP to those most likely to benefit and avoid unnecessary use that could speed up resistance.
Some have proposed making eligibility criteria more adaptable. For instance, the Kirby Institute has suggested that having one or two rectal STIs in the past year could suffice for eligibility. Others have pointed out a potential gap between strong community interest and limited clinical guidelines, which might unintentionally exclude individuals who would responsibly use Doxy-PEP and could benefit from it.
A recent national survey found that 76% of GBMSM would consider using Doxy-PEP. Those who had previously used antibiotics for STI prevention or were more familiar with the concept were more receptive to it. At the same time, many were aware of AMR and concerned about its implications. These findings suggest that the community is thoughtful about both the benefits and the risks.
Community organisations have a proven record of providing accessible, non-judgmental information to support informed decisions. That approach is especially important here. Messages about Doxy-PEP should acknowledge concerns about AMR, explain the known risks and benefits, and encourage people to discuss it with their doctor before starting.
Looking ahead, next steps could include:
- Expand targeted education for individuals at higher risk of STIs, especially those with recent infections, to ensure they are aware of Doxy-PEP as a prevention option.
- Encourage regular STI screening alongside Doxy-PEP use, in line with current clinical guidelines and highlight the importance of testing even when prevention strategies are being used.
- Create online self-assessment tools to help people evaluate their risk and decide if Doxy-PEP is appropriate for their situation, similar to tools previously made for HIV PrEP.
- Review eligibility criteria regularly as new evidence and community needs develop, ensuring access stays properly targeted but remains responsive to real-world use.
- Maintain collaboration among researchers, clinicians, and community organisations to ensure consistent messaging, evidence-informed practice, and shared decision-making.
- Monitor antimicrobial resistance and deliver timely, balanced updates to the community, building trust and transparency in the implementation of the intervention.
- Provide further guidance and education to clinicians and sexual health professionals supporting clients interested in taking Doxy-PEP.
Doxy-PEP is not a one-size-fits-all approach, but it offers an important additional option for STI prevention. When used appropriately, it could help lower infection rates, improve health outcomes, and ease the pressure on healthcare services. The key now is to ensure that those who need it most can access it and that everyone has the information needed to make confident and informed decisions.