More than 60 years since the “morning after” pill to prevent unwanted pregnancies became available in Australia, there’s a new kind of “morning after” pill on the scene — and for a very different reason.

Key points:

  • Doxy-PEP can be taken up to 72 hours after unprotected sex and is effective at preventing syphilis
  • The US is currently in the process of developing clinical guidelines for prescribing doxy-PEP
  • However there’s concern among some sexual health doctors about increasing antibiotic resistance

It’s to prevent some sexually transmitted infections (STIs) and while it sounds convenient, not everyone is convinced the benefits outweigh the risks.

After months of discussions, around 40 of Australia’s leading sexual health physicians have agreed that doxycycline post-exposure prophylaxis, known as “doxy-PEP”, should be considered for the prevention of some STIs among men who sleep with men.

The consensus statement, released by the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM), says the antibiotic can be given to men at high risk up to three days after unprotected sex.

The past decade has seen year-on-year increases in STIs among gay and bisexual men, and other men who have sex with men, despite significant efforts to curb the spread.

Co-author of the statement and sexual health specialist at the Kirby Institute Vincent Cornelisse says increases in syphilis infections have been particularly concerning, as they can affect the brain, heart and eyes if left undiagnosed.

Of all the bacterial STIs, syphilis carries the greatest risk among men who sleep with men.(Pexels: Ketut Subiyanto)

Syphilis among younger women is also on the rise. The latest surveillance report by the Department of Health found non-Indigenous women had the biggest proportional increase in syphilis rates in the past 12 months.

The ongoing outbreak of syphilis among Aboriginal and Torres Strait Islander people also continues, with rates seven times higher than non-Indigenous people, but the greatest proportion of infections is among non-Indigenous men in major cities.

Dr Cornelisse, a clinical advisor with ASHM, says Australians have been ordering doxy-PEP online without a prescription for years, so demand is only going to keep growing and doctors need to be ready to have conversations about the drug.

Clinical trials have shown doxy-PEP can reduce the chance of syphilis by between 70 and 80 per cent and chlamydia by 70 to 90 per cent, but is less effective for gonorrhoea (around 55 per cent reduction at best).

In the US, it’s already being prescribed by some STI clinics, and just last week, the Centers for Disease Control and Prevention released proposed guidelines on using doxy-PEP.

Earlier this year the World Health Organisation signalled it would consider the potential benefits of developing doxy-PEP guidelines.

But some experts fear widespread use could have unintended consequences on a global scale. 

How is it taken?

The drug, called doxycycline, is commonly prescribed if you test positive for chlamydia. It’s also used for syphilis infections if the patient can’t take penicillin.

Normally the recommended dose is 100 milligrams twice daily for seven days.

But using it to prevent an STI involves taking a single 200mg dose up to 72 hours after unprotected sex.

The ASHM says doctors might consider prescribing it for a pre-defined period, for example three to six months, so patients can get the antibiotic when they need it.

After this period, a review should take place to discuss ongoing use.

The consensus statement says prescribing doxy-PEP might be appropriate if the individual fits any of the following criteria:

  • has had a syphilis diagnosis within the past six or 12 months
  • has had two or more STI diagnosis that aren’t syphilis within the past six or 12 months
  • is about to have a period of heightened STI risk, such as holiday plans which involve sexual activity with multiple casual sexual partners
  • has concurrent male and female sexual partners.

The ASHM is primarily recommending doxy-PEP to prevent syphilis but says it could be used to prevent chlamydia and gonorrhoea in some individuals.

Some sexual health physicians involved in the consensus statement disagree on this though, with a minority saying it should be used only for the prevention of syphilis.

This is because most chlamydia infections among men have little impact on their health, and the bacterium that causes gonorrhoea in Australia is already highly resistant to doxycycline.

Why is it only for men who sleep with men?

There’s no evidence that doxy-PEP can prevent STIs among cisgender women.

A recent trial of the drug among 449 women in Kenya aged between 18 and 30 did not find the treatment effective but further analysis suggested this was because study participants did not take doxy-PEP as needed.

Dr Cornelisse says anatomical differences may have reduced effectiveness as well.

Researchers suggest that doxy-PEP may not prevent STIs in tissue within the endocervix (which connects the vagina to the uterus), but more research is needed.

Vincent Cornelisse says new approaches are needed to control rising STIs. (Supplied)

He says the effectiveness of doxy-PEP should also be considered for Indigenous people given the disproportionately high rates of syphilis in the community.

“This will require meaningful engagement and collaboration with affected communities.”

The ‘massive issue’ of antibiotic resistance

Antimicrobial resistance is always a major concern with increased antibiotic use.

It occurs when bad bacteria become resistant to the antibiotics used to kill them, and is one of the biggest global threats to human health.

Antibiotic-resistant bacteria can spread from person to person through, for instance, water and contaminated food.

A study by the Global Research on Antimicrobial Resistance (GRAM) Project published in The Lancet found an estimated 1.2 million people died from antibiotic-resistant infections in 2019.

It’s the reason the British Association for Sexual Health and HIV and the UK Health Security Agency have not endorsed doxy-PEP, stating that any potential benefits would be outweighed by the considerable potential of antibiotic resistance.

Dr Cornelisse says clinical trials have tested whether certain bacteria, including Staphylococcus aureus

which causes staph infections, are resistant to doxy-PEP. The results, he says, were “reasonably reassuring”.

However he says larger trials on a wider range of organisms are needed as antimicrobial resistance is a “massive issue” in sexual health medicine.

ASHM’s consensus statement says “uncertainty remains” about increased antimicrobial resistance and public health bodies should be appropriately funded to monitor for resistance.

But Fabian Kong, an epidemiologist and deputy head of the sexual health unit at the University of Melbourne, believes ASHM has jumped the gun by endorsing doxy-PEP before properly preparing the health system.

“They say ‘we don’t know much about resistance’ and ‘we need to keep monitoring it’ and I find that really, really wrong.

“They are saying public health pathology should be funded to monitor for antimicrobial resistance but that hasn’t been done. It would be extremely difficult and the government would have to pour lots and lots of money into pathology.

“Antimicrobial resistance is now going to develop, so how are we going to monitor that it’s killing people out there? We aren’t going to know.”

Fabian Kong says there needs to be big investments in monitoring for antibiotic resistance.(Supplied)

Dr Kong, who participated in roundtable discussions with ASHM, says he understands people want easy ways to control their sexual health that don’t involve lots of anxious visits to the doctor for STI testing.

But he says convenience isn’t worth antibiotic resistance.

He says doxy-PEP would make more sense in remote communities where access to health care is more challenging.

“But for people in an urban environment, they should just get tested regularly for STIs.”

What now?

ASHM says formal clinical guidelines for doctors on how to prescribe doxy-PEP will be developed once more evidence emerges.

But Dr Kong says GPs need clear directions now.

“What will GPs do when someone rocks up and asks for a doxy-PEP prescription?

“They will have to use their own knowledge about antimicrobial resistance to manage this. I would expect many of them would say no to using it as a preventive tool but others may say yes.”

Dr Cornelisse says the sexual health medicine sector takes antimicrobial resistance “very seriously”. Doxy-PEP should not be used as a population-wide intervention, he adds, but instead very selectively for those at the highest chance of becoming infected.

He says ideally it would be delivered as part of a comprehensive HIV and STI prevention package which includes regular testing, HIV pre-exposure prophylaxis (PrEP), condoms and vaccinations for HPV, Hepatitis A and Hepatitis B.

Some advocates for doxy-PEP, such as Dr Cornelisse, argue that getting STI transmission under control with the drug’s help could ultimately lead to an overall reduction in antibiotic use.

But recent research by researchers at Harvard and the Institute of Tropical Medicine in Belgium didn’t make favourable findings on this hypothesis.

They found using doxy-PEP as a preventative might reduce use of some antibiotics (such as ceftriaxone and azithromycin) but that would effectively be cancelled out by increasing doxy-PEP uptake.

Many sexual health experts believe the development of vaccines for bacterial STIs is the best way forward, but research investment in this area isn’t strong, given there are effective treatments for these infections.

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