From the Guidelines
For patients with a penicillin (PCN) allergy who require treatment for sexually transmitted infections (STIs), doxycycline 100 mg orally twice daily for 14 days is a preferred alternative for syphilis treatment, as evidenced by the 2010 guidelines 1. When considering treatment options for STIs in patients with PCN allergy, it's crucial to prioritize alternatives that are effective and have a low risk of cross-reactivity.
- For syphilis, doxycycline is a viable option due to its efficacy and better compliance compared to tetracycline, which can cause gastrointestinal side effects 1.
- Azithromycin, although effective as a single 2-g oral dose for early syphilis, should be used with caution due to reported resistance and treatment failures, particularly in certain geographical areas and populations such as MSM or pregnant women 1.
- Ceftriaxone, with its potential for effectiveness in treating early syphilis, lacks defined optimal dose and duration, making it a less straightforward choice 1. Given the potential severity of PCN allergies and the importance of effective STI treatment, doxycycline emerges as a reliable alternative for patients allergic to penicillin, especially when considering the need for high compliance and the potential for resistance with other options. Key considerations include:
- The nature and severity of the PCN allergy
- The specific STI being treated
- The potential for cross-reactivity with other antibiotics
- The need for close follow-up, especially when using alternative therapies 1.
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. Nongonococcal urethritis (NGU) caused by C. trachomatis or U. urealyticum: 100 mg, by mouth, twice a day for 7 days. Acute epididymo-orchitis caused by N. gonorrhoeae: 100 mg, by mouth, twice a day for at least 10 days. Acute epididymo-orchitis caused by C. trachomatis: 100 mg, by mouth, twice a day for at least 10 days
For patients with a PCN allergy, the recommended treatment for various STIs using doxycycline is as follows:
- Syphilis: 100 mg, twice a day for 2 weeks (early) or 4 weeks (more than one year’s duration) 2
- Gonococcal infections: 100 mg, twice a day for 7 days 2
- Chlamydia trachomatis: 100 mg, twice a day for 7 days 2
- Nongonococcal urethritis: 100 mg, twice a day for 7 days 2
- Acute epididymo-orchitis: 100 mg, twice a day for at least 10 days 2 Metronidazole can be used to treat Trichomoniasis in patients with a PCN allergy, with a recommended dosage of 2 grams as a single dose or 250 mg three times daily for seven consecutive days 3
From the Research
STI Treatment with PCN Allergy
- For patients with a penicillin (PCN) allergy, alternative treatments are available for various sexually transmitted infections (STIs) 4, 5, 6.
- In the case of gonorrhea, ceftriaxone monotherapy is the recommended treatment, but patients with a PCN allergy may be less likely to receive this treatment 5.
- For syphilis, doxycycline is an acceptable alternative to penicillin for early and late latent syphilis if penicillin cannot be used 6.
- Doxycycline postexposure prophylaxis may also be considered for preventing STIs such as syphilis, gonorrhea, and chlamydia in certain clinical scenarios 7.
Alternative Treatments
- Metronidazole, doxycycline, and levofloxacin are alternative antibiotics that may be prescribed for patients with a PCN allergy 5.
- A penicillin allergy screening algorithm and penicillin skin testing can be used to transition hospitalized patients from second-line to first-line antibiotic therapy 8.