Antibiotics the Morning After may decrease risk of STDs

A new clinical trial has found that a morning-after dose of the antibiotic doxycycline can significantly reduce the risk of sexually transmitted bacterial infections in high-risk individuals. Participants in the trial, which focused on gay and bisexual men and transgender women who had HIV or were taking medication to prevent it, were two-thirds less likely to be diagnosed with gonorrhea, chlamydia and syphilis after taking doxycycline within 72 hours of unprotected sex. The benefits were so convincing that the trial was stopped early. The incidence of STIs every three months was around 11% in the doxycycline group, compared to over 30% in the comparison group. The preventive measure was most effective against chlamydia and syphilis, cutting the risks by close to 90% in HIV-negative people and by over 70% in those with HIV. The efficacy against gonorrhea was less, but infections were still reduced by 55%. The trial involved specific groups at high risk of bacterial STIs, and no one is suggesting that everyone should take doxycycline after unprotected sex. However, for people at high risk, the benefits of preventive doxycycline could well outweigh the theoretical risk of altering the microbiome in a harmful way. It is also important to note that the trial involved certain groups who are at particularly high risk of bacterial STIs, and any STI preventive measure should be seen as part of a package, which may include condom use, frequent STI screening and vaccination against hepatitis B, for instance. While wider use of the antibiotic could increase bacterial resistance to doxycycline, there has never been any documented resistance of syphilis or chlamydia to the drug. However, some gonorrhea strains are resistant to the antibiotic, and it is possible that with time, morning-after doxycycline will become less effective in preventing gonorrhea. It is important to talk to a doctor to determine if doxycycline is right for you. Cisgender women were not included in this trial, and it is unknown if morning-after doxycycline is effective for them.