What is sexually transmitted infection (STI) prophylaxis in patients with a penicillin allergy?

From the Guidelines

For STI prophylaxis in patients with penicillin allergy, the recommended alternative is doxycycline, as stated in the 2024 CDC clinical guidelines 1. This regimen is effective against common bacterial STIs like chlamydia and syphilis. Key points to consider when prescribing doxycycline for STI prophylaxis include:

• Starting treatment as soon as possible after potential exposure, ideally within 24-72 hours
• Using doxycycline 100 mg orally twice daily for 7 days, as this dosage has been shown to be effective in preventing STIs 1
• Noting that doxycycline is not currently recommended for the treatment of gonorrhea due to elevated antimicrobial resistance, but it remains effective against many strains of N. gonorrhoeae in the United States 1 For patients who cannot take doxycycline (e.g., pregnant women), alternative options should be considered, such as azithromycin 1 gram orally as a single dose, although its use should be cautious due to potential resistance 1. Remember that this prophylaxis does not protect against all STIs, particularly viral infections like HIV or herpes. Patients should still be advised to:
• Use barrier methods (condoms)
• Get tested regularly Doxycycline is preferred because it has a broad spectrum of activity against many bacterial pathogens and good tissue penetration, as well as a longer half-life, allowing for less frequent dosing compared to other antibiotics 1. If the patient has a history of severe allergic reactions to antibiotics, they should consult with an allergist before starting any prophylaxis regimen.

From the FDA Drug Label

Syphilis–early: Patients who are allergic to penicillin should be treated with doxycycline 100 mg, by mouth, twice a day for 2 weeks Syphilis of more than one year’s duration: Patients who are allergic to penicillin should be treated with doxycycline 100 mg, by mouth, twice a day for 4 weeks. Uncomplicated gonococcal infections in adults (except anorectal infections in men):100 mg, by mouth, twice a day for 7 days. Uncomplicated urethral, endocervical, or rectal infection in adults caused by Chlamydia trachomatis: 100 mg, by mouth, twice a day for 7 days. Urethritis and cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae.

For STI prophylaxis in patients with a penicillin allergy, the recommended treatments are:

• Doxycycline 100 mg, by mouth, twice a day for the specified duration, for the prevention of syphilis and other STIs 2
• Azithromycin may be used as an alternative for the treatment of certain STIs, such as chlamydia and gonorrhea, but its use for prophylaxis is not explicitly stated in the provided drug label 3 Key points:
• Doxycycline is recommended for the treatment of syphilis and other STIs in patients with a penicillin allergy.
• Azithromycin may be used as an alternative for the treatment of certain STIs, but its use for prophylaxis is not explicitly stated.

From the Research

STI Prophylaxis in Patients with a Penicillin Allergy

• Patients with a penicillin allergy may require alternative treatments for sexually transmitted infections (STIs) 4, 5, 6, 7, 8
• Doxycycline is a recommended treatment for several STIs, including syphilis, chlamydia, and gonorrhea, and can be used as prophylaxis in patients with a penicillin allergy 4, 5, 6, 7, 8
• Azithromycin is another alternative treatment for STIs, including gonorrhea and chlamydia, and has been shown to be effective in a single dose regimen 5

Doxycycline Prophylaxis

• Doxycycline prophylaxis has been shown to be effective in preventing syphilis and other STIs in high-risk populations, including gay, bisexual, and other men who have sex with men 6, 8
• The use of doxycycline prophylaxis is recommended for patients at high risk of syphilis, and may also provide secondary benefits in reducing other bacterial STIs 8
• However, there are concerns about the potential for increasing antimicrobial resistance with the use of doxycycline prophylaxis, and its use should be carefully considered and monitored 6, 8

Treatment Guidelines

• The Centers for Disease Control and Prevention (CDC) provides updated guidelines for the treatment of STIs, including recommendations for patients with a penicillin allergy 7
• The CDC recommends doxycycline as the preferred treatment for chlamydia, and ceftriaxone monotherapy for gonorrhea, with alternative treatments available for patients with a penicillin allergy 7