May 8, 2023 – “Think of it like the morning-after pill, but for sexually transmitted diseases,” said Aniruddha Hazra, MD, PhD, who focuses on infectious diseases within the Division of Infectious Diseases and Global Health on the University of Chicago Medicine.
The reason for this big statement? New research shows that the antibiotic doxycycline reduces the incidence of HIV and sexually transmitted infections (STIs) after contact with the antibiotic by two-thirds.
“While the morning-after pill can be a prophylaxis (or prevention) against pregnancy, doxycycline can be taken shortly after sexual contact or possible contact with an STI to prevent infection,” said Hazra, who was not involved within the study.
The recent research from the National Institutes of Health aimed to bolster previous case studies of doxycycline in a clinical trial of men who've sex with men, said lead researcher Anne Luetkemeyer, MD, an infectious disease specialist on the University of California, San Francisco.
Previous studies from France in 2016 appeared to indicate that doxycycline – or doxy – was effective against sexually transmitted diseases, but Luetkemeyer's team wanted to substantiate those results and study the effect in a special population, she said.
This randomized controlled trial found that doxycycline reduced the incidence of sexually transmitted infections equivalent to chlamydia and syphilis. Men assigned male at birth showed advantages with a two-thirds prevention rate. A 2022 study of girls in Kenya showed that doxycycline provides limited to no prevention.
Doxycycline is an antibiotic within the tetracycline group. Like all antibiotics, it stops or slows down bacterial infections, but not viral ones. Doxycycline is used to treat anthrax, malaria, pimples, and other conditions. A prescription for the antibiotic costs just a couple of cents if you've insurance.
The April in New England Journal of Medicine demonstrates the broader use of doxycycline in reducing HIV and STIs amongst men who've male sex and in transgender women.
The government-funded 2023 study shows that study participants who reported having had a sexually transmitted infection prior to now 12 months reduced their risk of re-infection by two-thirds due to the protection of the antibiotic.
The study, led by researchers on the University of California, San Francisco and the University of Washington, involved about 500 adults from 4 clinics in San Francisco and Seattle. All study participants were assigned male at birth, reported sexual intercourse and had received an STI or HIV diagnosis prior to now.
The study found that 10.7% of patients taking doxycycline received an STI diagnosis in comparison with 31.9% of the control group – a two-thirds reduction in STI cases. HIV diagnosis among the many doxycycline patients was 11.8% in comparison with 30.5% within the control group – also a virtually two-thirds reduction.
Although there have been no reports of doxycycline resistance within the chlamydia or syphilis cases, Luetkemeyer said researchers are currently studying doxy-PrEP strains in individuals who have experienced breakthrough infections to search for evidence of resistance.
“We definitely have to keep an eye on this possibility,” said Luetkemeyer. “But it simply hasn't been described yet. And certainly many cases of syphilis and chlamydia have been treated with doxycycline.”
Trevor Hedberg, physician assistant and director of the sexual and reproductive health walk-in clinic at Howard Brown Health in Chicago, said two patients prior to now six months mentioned doxycycline as a pre-exposure treatment. He said the clinic typically recommends doxycycline for individuals who were assigned male at birth, engage in sex work or have been diagnosed with syphilis prior to now.
“You know, my approach to conversations about doxy PrEP is based on the STI history,” Hedberg said. “How the patient assesses their risk of STI infection, and we discuss the side effects and safety profile of doxycycline and whether it's safe for them to take it.”
Over the years, acceptance of using Doxy to guard against infection has increased, and the most important concern is antibiotic resistance, says Zach Bird, a health educator on the Center on Halsted, a community center dedicated to the health of LGBTQ+ people within the Chicago area.
“I understand why research on Doxy is necessary because there are more recorded cases of bacterial sexually transmitted diseases and syphilis,” Bird said.
At first, “many individuals shamed the individuals who [doxy] PrEP to have more sex. I don't really see that, not less than not in the neighborhood I serve,” Bird said. “But the people I've heard from are inclined to say, you don't know if resistance will construct up, if it's going to change into super gonorrhea over time or something like that.”
The reduction in STIs and HIV by doxycycline is particularly applicable to those who were assigned male at birth.
“I'd say that within the meantime, until we've got more information on cisgender women, this is just not a population for whom doxy-PrEP is really helpful,” Luetkemeyer said. “I'd also say that this is just not yet an actual intervention for the overall population.”
Hazra said doxycycline has been one of the most commonly prescribed antibiotics in France over the past five years since the ANRS study. However, he advised against prescribing it to pregnant women because of the potential for tetracycline to cause birth defects such as tooth discoloration and bone abnormalities.
The CDC has published considerations for prescribing doxycycline, but no detailed guidelines. The San Francisco Department of Public Health, where Luetkemeyer practices, has issued recommendations for cisgender men and trans women.
Men who have sex with men are among the group most at risk from HIV. According to the CDC, the lifetime risk of HIV infection among MSM is 1 in 6, compared to 1 in 524 among heterosexual men and 1 in 253 among heterosexual women.
“I find [doxy PrEP] is a extremely good tool for individuals who need additional STI prevention measures, and our approach is to supply this to the people who find themselves most in danger,” Lütkemeyer said.