July 13, 2024

Consuming the antibiotic doxycycline after sex can significantly reduce the chances of getting a sexually transmitted disease (STI) like chlamydia or early syphilis, a study revealed. 

According to the findings presented at the Conference on Retroviruses and Opportunistic Infections in Denver, a single dose of the widely used antibiotic doxycycline taken after sexual intercourse has reduced the incidences of chlamydia and early syphilis among gay and bisexual men and transgender women by half in San Francisco, California.

Researchers gave a supply of the antibiotic to gay and bisexual men and transgender women who had a history of STIs or multiple sex partners and asked them to consume two 100-milligramme pills within 72 hours of unprotected sex. This strategy is known as doxy-PEP, short for doxycycline post-exposure prophylaxis. 

The new cases of chlamydia and early syphilis dropped over about a year in the city. Dr Hyman Scott, medical director at the San Francisco Department of Public Health, said, “It’s not subtle, it is very fast and we’re seeing the beginning of it, not the end. This is what we want for STI prevention.”

However, the evidence supports the doxycycline case only in gay and bisexual men and transgender women. Dr Jonathan Mermin, director of the National Center for HIV, Viral Hepatitis, STD and TB Prevention at the Centers for Disease Control and Prevention (CDC), said, “The majority of STIs in the United States occur in cisgender women. Studies of whether doxy-PEP works in cisgender women should be implemented as quickly as possible.” 

CDC will release the final guidelines for doxy-PEP in the next few months, Dr Mermin said.

While cases of chlamydia and early syphilis decreased in gay and bisexual men and transgender women, the cases of chlamydia steadily increased in cisgender women. 

“The fact that we did not see declines in STIs in other populations not recommended for doxy, specifically cis women, strengthens the conclusion that the decline in chlamydia and early syphilis cases is related to doxy-PEP rollout,” said Madeline Sankaran, an epidemiologist at the San Francisco Department of Public Health who presented the findings.

Although the findings seem promising, Dr Merimin warned that the 2022 outbreak of mpox may have skewed them, as, during the period, high-risk groups reduced sexual activities. The rates of gonorrhoea did not see any significant changes, he added.

(With inputs from agencies)


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