Syphilis Treatment-Penicillin Allergy

Question

I have recently tested positive for Syphillis - probably contracted in the past 6 - 8 months. I am also HIV+ for about 18 years. Otherwise healthy and doing well on meds with CD4 >600. For the longest time, I have been telling medical staff that I am allergic to penicillin and sulfa drugs. Although I have a clear memory of the allergic reaction I had to Bactrim- rash fever chills... no doubt an allergic reaction - I honestly don't remember when I had such a reaction to penicillin. I know I was given it when I was a kid. But somewhere along the line, I don't remember exactly when, I started telling people I was allergic to penicillin. Maybe it coincided with the Bactirm experience 15-20 years ago. I just don't remember. So now that I need treatment for Syphilis, my Dr wants to desensitize me to penicillin, do a tap-line and hook me up to a portable pump for 2 weeks of steady low-dose penicillin, recommended for patients with penicillin allergy. I asked if before we take that route, we confirm that I truly am allergic to penicillin. He said it was too risky considering the large amount of penicillin that's given to treat Syph to non-allergic patients. Even if the scratch-test for penicillin allergy shows no reaction, the chance that there is a latent reaction is too great. So 2 questions...

  1. Can a scratch-test be relied on to confirm or not a penicillin allergy and if no reaction, is it safe to proceed with normal treatment for Syph?
  2. Are there alternate antibiotics that can affectively treat Syph? If I have to go the tap-line, desensitization, pump route, I will. But just want to explore any other options available. thank you very much for your time.

Answer

The scratch test is of some clinical benefit in this setting. Even with a negative scratch test if the history for pen allergy is strong then a desensitization procedure may be advisable. If the history for pen allergy is weak and there is a negative scratch test then proceding with use of penicillin under observation is an option. I generally would recommend desensitization if uncertain. Pencillin is the gold standard for syphilis treatment. Data with a tetracycline or ceftriaxone suggests a higher failure rate than with penicillin. KH