From the Guidelines
Doxycycline is a broad-spectrum antibiotic that covers a wide range of bacterial infections, including Lyme disease, human granulocytic anaplasmosis (HGA), and certain sexually transmitted infections (STIs) like chlamydia and syphilis, as well as other infections such as respiratory, skin, and soft tissue infections. It is effective against many gram-positive bacteria (including Staphylococcus and Streptococcus species), gram-negative bacteria (such as Escherichia coli, Klebsiella, and Haemophilus influenzae), and atypical organisms (like Mycoplasma, Chlamydia, and Rickettsia) 1. Some key points to consider when using doxycycline include:
- The typical adult dose is 100mg twice daily or 200mg once daily, usually for 7-14 days depending on the infection being treated 1.
- Doxycycline works by inhibiting bacterial protein synthesis by binding to the 30S ribosomal subunit, preventing bacteria from producing essential proteins needed for survival and reproduction 1.
- It should be taken with plenty of water and patients should remain upright for at least 30 minutes after taking it to prevent esophageal irritation 1.
- Notably, doxycycline should be avoided in pregnant women and children under 8 years due to the risk of dental staining and bone growth issues 1.
- Doxycycline is also used as postexposure prophylaxis (PEP) for bacterial STIs, with a recommended dose of 200mg taken as soon as possible within 72 hours after sex, with a maximum dose of 200mg every 24 hours 1. The most recent and highest quality study on the use of doxycycline for STI prevention was published in 2024, which demonstrated significant reductions in bacterial STI acquisition (syphilis, chlamydia, and gonorrhea) among men who have sex with men (MSM) and transgender women (TGW) 1. Overall, doxycycline is a valuable antibiotic for the treatment and prevention of various bacterial infections, and its use should be guided by current clinical guidelines and recommendations 1.
From the FDA Drug Label
Doxycycline is indicated for the treatment of the following infections: Rocky Mountain spotted fever, typhus fever and the typhus group, Q fever, rickettsialpox, and tick fevers caused by Rickettsiae. Respiratory tract infections caused by Mycoplasma pneumoniae. Lymphogranuloma venereum caused by Chlamydia trachomatis. Psittacosis (ornithosis) caused by Chlamydia psittaci. Trachoma caused by Chlamydia trachomatis, although the infectious agent is not always eliminated, as judged by immunofluorescence. Inclusion conjunctivitis caused by Chlamydia trachomatis. Uncomplicated urethral, endocervical, or rectal infections in adults caused by Chlamydia trachomatis. Nongonococcal urethritis caused by Ureaplasma urealyticum. Relapsing fever due to Borrelia recurrentis. Doxycycline is also indicated for the treatment of infections caused by the following gram-negative microorganisms: Chancroid caused by Haemophilus ducreyi. Plague due to Yersinia pestis (formerly Pasteurella pestis). Tularemia due to Francisella tularensis (formerly Pasteurella tularensis). Cholera caused by Vibrio cholerae (formerly Vibrio comma). Campylobacter fetus infections caused by Campylobacter fetus (formerly Vibrio fetus). Brucellosis due to Brucella species (in conjunction with streptomycin). Bartonellosis due to Bartonella bacilliformis. Granuloma inguinale caused by Calymmatobacterium granulomatis. Doxycycline is indicated for treatment of infections caused by the following gram- negative microorganisms, when bacteriologic testing indicates appropriate susceptibility to the drug: Escherichia coli. Enterobacter aerogenes (formerly Aerobacter aerogenes). Shigella species. Acinetobacter species (formerly Mima species and Herellea species). Respiratory tract infections caused by Haemophilus influenzae. Respiratory tract and urinary tract infections caused by Klebsiella species. Doxycycline is indicated for treatment of infections caused by the following gram-positive microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug: Upper respiratory infections caused by Streptococcus pneumoniae (formerly Diplococcus pneumoniae) Anthrax due to Bacillus anthracis, including inhalational anthrax (post-exposure): to reduce the incidence or progression of disease following exposure to aerosolized Bacillus anthracis.
Doxycycline covers a wide range of bacterial infections, including:
- Rickettsial infections: Rocky Mountain spotted fever, typhus fever, Q fever, rickettsialpox, and tick fevers
- Chlamydial infections: Lymphogranuloma venereum, psittacosis, trachoma, inclusion conjunctivitis, and uncomplicated urethral, endocervical, or rectal infections
- Gram-negative microorganisms: Haemophilus ducreyi, Yersinia pestis, Francisella tularensis, Vibrio cholerae, Campylobacter fetus, Brucella species, Bartonella bacilliformis, and Calymmatobacterium granulomatis
- Gram-positive microorganisms: Streptococcus pneumoniae and Bacillus anthracis
- Other infections: Relapsing fever, nongonococcal urethritis, and infections caused by Escherichia coli, Enterobacter aerogenes, Shigella species, Acinetobacter species, Haemophilus influenzae, and Klebsiella species 2
From the Research
Overview of Doxycycline Coverage
- Doxycycline is a broad-spectrum antimicrobial agent used to manage various bacterial infections, including sexually transmitted infections (STIs) 3.
- It has high bioavailability and a long elimination half-life, allowing for oral administration of one or two daily doses 3.
Doxycycline and Sexually Transmitted Infections
- Doxycycline is effective in treating STIs such as syphilis, chlamydiosis, gonorrhea, and Mycoplasma genitalium infections 3, 4, 5.
- A one-time dose of 200 mg doxycycline taken within 72 hours of an unprotected sexual encounter may reduce transmission of syphilis, gonorrhea, and chlamydia by a combined two thirds in a high-risk population 4.
- Doxycycline prophylaxis shows promise in preventing bacterial STIs, with high efficacy and good tolerability 5, 6.
Specific STIs Covered by Doxycycline
- Syphilis: doxycycline is effective in treating syphilis, with a significant reduction in transmission rates 4, 6.
- Chlamydia: doxycycline is effective in treating chlamydia, with a significant reduction in transmission rates 4, 6, 7.
- Gonorrhea: doxycycline is effective in treating gonorrhea, but resistance rates are a concern 6, 7.
- Mycoplasma genitalium infections: doxycycline is effective in treating Mycoplasma genitalium infections 3.