From the Guidelines
For patients with penicillin allergy who need treatment for syphilis, doxycycline is the preferred alternative therapy, with a recommended regimen of 100 mg orally twice daily for 14 days 1. This recommendation is based on the limited data available for alternative treatments to penicillin in syphilis, as outlined in the 2010 sexually transmitted diseases treatment guidelines 1. Key points to consider in the treatment of syphilis in patients with penicillin allergy include:
- Doxycycline and tetracycline are potential alternatives, but doxycycline is preferred due to better compliance and fewer gastrointestinal side effects 1.
- Azithromycin may be effective but should be used with caution due to resistance and treatment failures, especially in certain populations like men who have sex with men (MSM) or pregnant women 1.
- Ceftriaxone is another option, but the optimal dose and duration of therapy have not been defined 1.
- Desensitization to penicillin should be considered for pregnant patients or those who cannot take tetracyclines, as penicillin remains the most effective treatment 1.
- Confirming the penicillin allergy is crucial before starting alternative therapy, as many reported allergies may not be genuine 1.
- Follow-up serologic testing at 6 and 12 months after treatment is essential to ensure an adequate response, regardless of the regimen used 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.
- The best treatment for syphilis in patients with a penicillin allergy is doxycycline.
- The recommended dosage is 100 mg, by mouth, twice a day.
- The treatment duration depends on the duration of the syphilis infection:
- For early syphilis (less than 1 year), the treatment duration is 2 weeks.
- For syphilis of more than one year’s duration, the treatment duration is 4 weeks 2.
From the Research
Treatment Options for Syphilis in Penicillin Allergy
- The primary treatment for syphilis is penicillin G, but in cases of penicillin allergy, alternative treatments must be considered 3, 4, 5.
- Azithromycin has been studied as a potential alternative to penicillin for the treatment of early syphilis, with some studies suggesting similar efficacy 6, 7.
- A meta-analysis of randomized controlled trials found no significant difference in response rates between azithromycin and penicillin for the treatment of early syphilis 7.
- However, the emergence of azithromycin resistance in Treponema pallidum has raised concerns about its use as a first-line treatment 3, 5.
Considerations for Treatment
- The choice of treatment for syphilis in penicillin allergy should be based on the stage of the disease, the presence of any comorbidities, and the patient's overall health status 4, 5.
- Cerebrospinal fluid examination should be performed in all persons with serologic evidence of syphilis infection and neurologic symptoms 5.
- HIV-infected persons with syphilis may require more frequent monitoring and follow-up to ensure adequate treatment response 4, 5.
Efficacy of Azithromycin
- Studies have shown that azithromycin is effective in treating early syphilis, with cure rates similar to those of penicillin 6, 7.
- However, the development of azithromycin resistance is a concern, and its use should be carefully considered in areas where resistance is prevalent 3, 5.
- Further research is needed to fully understand the efficacy and safety of azithromycin for the treatment of syphilis, particularly in penicillin-allergic patients 6, 7.