A single-dose morning-after pill could be introduced to tackle rising rates of syphilis in the UK.
New guidelines are being developed on the use of doxyPEP, the antibiotic doxycycline, which trials show can be given within 24 hours of unprotected sex to prevent the development of a life-threatening sexually transmitted infection (STI).
Experts say the approach could be “a valuable tool” in the fight against syphilis, which was almost eradicated in the UK in the 1990s but has re-emerged in recent years.
Doxycycline, which costs pennies, is already prescribed to treat syphilis and chlamydia, another STI, and is typically taken every day for up to two weeks to eradicate the infection. However, research into the effect of a single high dose found that it could stop infections from occurring.
The study involved around 500 participants who had had an STI in the previous year. Some were given doxyPEP to take after having sex without a condom – including oral sex – along with the standard care of regular STI testing every three months and treatment if an infection was detected. Others received standard care without doxyPEP.
A single-dose ‘morning after’ pill could be introduced to tackle rising rates of syphilis in the UK.
The risk of syphilis infection, which can cause serious heart and brain problems, was almost 90 percent lower in the doxyPEP group and STI infections were reduced by two-thirds overall.
In October, US regulators, the Centers for Disease Control (CDC), issued guidance recommending doxyPEP to reverse the country’s syphilis crisis, which has seen an 80 percent increase in cases since 2018. The most recent increases Pronounced cases have occurred in the most disadvantaged areas, where access to health care is scarce.
The main concern in the United States is that the disease could be transmitted from mothers to babies during pregnancy or shortly after birth.
This disease, known as congenital syphilis, can have tragic consequences, including miscarriage, stillbirth, infant death, and lifelong medical problems.
More than 3,700 babies in the US were born with syphilis in 2022.
The risk of syphilis infection, which can cause serious heart and brain problems, was almost 90 percent lower in the doxyPEP group and STI infections were reduced by two-thirds overall.
“The United States has a major problem with congenital syphilis, and that is what worries us most if cases continue to rise,” said Dr. John McSorley, a London-based consultant in genitourinary medicine and HIV.
“In the UK it mainly affects men who have sex with men.”
Last month it was reported that sexual health services in England were grappling with “unprecedented” increases in demand. According to the Local Government Association (LGA), two-thirds of municipal areas experienced increases in syphilis and gonorrhea rates. Overall, there was a 76 percent increase in syphilis rates and a 36 percent increase in chlamydia rates.
An LGA analysis found that between 2015 and 2024, public health funding received by councils was reduced by £880 million, resulting in a reduction in testing, contraception and STI treatment.
Professor Matt Phillips, president of the British Association for Sexual Health and HIV (BASHH), responsible for producing guidance on sexual health treatments for doctors, said its working groups were “taking care” to produce guidance on doxyPEP for the United Kingdom.
“We’re trying to understand who it might be useful to,” he said. “It will be a useful tool for the right people.” He added that the “spectrum” of drug-resistant superbugs looms large. In the UK, another common infection, gonorrhea, is increasingly immune to doxycycline and other first-line antibiotics.
Antibiotic resistance occurs when bacteria are exposed to drugs but are not completely killed, which can happen if patients do not complete treatment.
Last month it was reported that sexual health services in England were grappling with “unprecedented” increases in demand.
Surviving bacteria can develop defense mechanisms against the antibiotic. Once they multiply, they are much more difficult to treat.
“There is concern that if people take doxyPEP when they unknowingly have gonorrhea, drug resistance could worsen,” Professor Phillips said. “We would need to ensure that patients receiving doxyPEP have regular check-ups.”
Dr. McSorely added that doxyPEP would be recommended alongside standard approaches. “Syphilis takes up to three months to cause symptoms, and during that time people can transmit it without realizing it,” he said.
‘We recommend that all sexually active people get tested once a year, and if they have had a new partner they should also get tested.
‘If it is detected, we have 100 percent effective treatments and we can carry out contact tracing, which is the best way to detect infection in asymptomatic people.
‘A third of people diagnosed with syphilis had no idea something was wrong. We also encourage the use of condoms as they are very effective in preventing most STIs.’
Some private online clinics are promoting doxyPEP, stating that it is “a no-brainer” for preventing syphilis.
But Dr. McSorley urged caution. “The dose of doxyPEP is high; on an empty stomach it would probably cause vomiting,” he said. “It can also cause photosensitivity, where the skin blister when exposed to even mild sunlight.”
