Easy to get, but not always easy to treat - Clinical and serological failure with Azithromycin in Syphilis: Time to adapt national guidelines?

Data since 2014 has shown a rise in the incidence of Syphilis especially amongst heterosexuals. In national guidelines, Macrolides remain an alternative treatment option although their efficacy has been long disputed.

We describe a case of a patient with clinical and serological failure with Azithromycin treatment.

Methods

A 46 year old female presented with painful genital ulceration confirmed as primary syphilis. Sexual transmission infection testing was negative. She described an allergy (rash) to Amoxicillin and was given Doxycycline 100mg twice daily for 14 days. On day 5 she developed an urticarial rash and was changed to Azithromycin, 2g stat and 500mg daily for 10 days.

There was initial serological response in her rapid plasma reagin (RPR) to 1:2 from 1:8 at 1 month, but at 5 months an RPR of 1:64 was seen with signs of secondary syphilis - a rash and a sore mouth. Re-infection was ruled out, she was re-treated with Azithromycin and her RPR reduced to 1:2, but she had a persistent macular rash.

Following review by Infectious Diseases, 14 days of intravenous Ceftriaxone 1g daily was given. On day 10, her RPR rose to 1:64 but 3 months after fell to 1:4 and has been serofast since without further signs of Syphilis.

Patients treated with Macrolides should be closely monitored. Consideration should be given for desensitisation in patients with reported Penicillin allergy. As with pregnancy, consideration should be given to the removal of Azithromycin as an alternative treatment in national guidelines.