A medical study has found taking a single dose of the antibiotic doxycycline after sex significantly reduces the risk of catching chlamydia, gonorrhoea or syphilis.
The University of California in San Francisco has been studying hundreds of men who have bareback sex with other men.
They were testing something called doxycycline post-exposure prophylaxis (DoxyPEP), in which men take a 200 milligram dose of the drug within three days of having condomless sex.
The trial has now been stopped ahead of schedule because the results were so overwhelming – DoxyPEP reduced the risk of STIs by 65%.
Dr Will Nutland, an HIV researcher and co-founder of PrEPster.info said: “This research is good news. We know lots of men are already using DoxyPEP or DoxyPrEP (pre-exposure) and this research provides additional data to support that use.
“That’s not to say gay men should rush out to get doxycycline. Lots of people in the medical field have concerns about using antibiotics in this way. So it’s important to understand the pros and cons.
“I definitely think the research is pointing to this being an effective way of reducing STIs for some of us.”
This research is good news… [it] is pointing to this being an effective way of reducing STIs for some of us.
A number of community surveys in recent years showed that around one in 10 men who took PrEP for HIV had also used doxycycline as a preventative tool for other STIs. Most of those men obtained the antibiotic drugs privately, such as by buying them from online pharmacies.
Dr Nutland added: “There’s the potential for DoxyPEP and DoxyPrEP, when targeted to key populations of people, to reduce STIs in our communities as whole.
“Without available vaccines for all of these common STIs, the use of DoxyPEP and DoxyPrEP will act as a stop-gap strategy to proactively prevent these STIs within our queer communities.”
The study, which also included trans women, has not yet looked at whether using doxycycline in this way might increase the risk of antibiotic resistance or damage to the gut.
Professor of infectious diseases Dr Annie Luetkemeyer, who led the DoxyPEP study, said using doxycycline in this way could successfully lower the prevalence of STIs among the likes of gay men.
She said: “At this point, doxycycline after sex is a targeted intervention for certain populations, in this case men who have sex with men or transgender women who have already had an STI in the past year.
“Doxycycline as post-exposure prophylaxis may be similar to HIV pre-exposure prophylaxis (PrEP), which isn’t for everyone, but is an effective strategy for those at increased risk for HIV infection.”
STIs such as chlamydia, gonorrhoea and syphilis have been on the rise in most parts of the world for the past several years.
The trial followed 554 participants, with some of them being given doxycycline after having bareback sex and some not.
Data showed those who did receive the drug had substantially fewer infections compared with those on the trial who didn’t take it.
There was no difference in the effectiveness of the drug between men who were living with HIV and those who were HIV negative and taking PrEP.