Thank you for your inquiry.
Unfortunately I don't think there is a definitive answer to any of the salient but difficult questions you pose. At least none of which I am aware. But I will "weigh in" with my thoughts and then ask Dr. Roland Solensky, who is the coauthor of the Joint Task Force Parameters on Drug Reactions and a nationally recognized authority on adverse reactions to antibiotics, to respond as well. When we hear from Dr. Solensky, we will forward his response to you as well.
1. Do you recommend patch testing to these drugs? No. In my opinion patch testing to discern the cause of a systemic reaction of this nature has not been validated to the extent that the results would be trustworthy.
2. Would you do provocation testing? I am not aware of any other way to establish a cause and effect relationship between the antibiotic(s) and the symptoms. But would not do so now (certainly a debatable opinion). I would wait as long as could since you still have macrolides available.
3. What do you recommend to the pediatrician should there be another need for antibiotics? Macrolides
Thank you again for your inquiry. And I will forward Dr Solensky's response when we receive it.
Phil Lieberman, M.D.
We received a response from Dr. Roland Solensky. Thank you again for your inquiry, and we hope this response is helpful to you.
Phil Lieberman, M.D.
Response from Dr. Roland Solensky:
These reactions are somewhat unusual because 1) they both occurred after discontinuation of the antibiotics, 2) they were non-pruritic, and 3) were associated with fever. Also, many cutaneous eruptions are the result of both an antibiotic and the underlying infection, especially viral infections, but for the 2nd episode there wasn’t a respiratory infection being treated, the antibiotics were used for prophylaxis after a laceration.
I agree that patch testing isn’t worthwhile doing because the result (which will almost certainly be negative) would not change management. There are inconsistent data on usefulness of patch testing in different drug-induced skin eruptions, such as maculopapular rashes, DRESS, SJS/TEN, AGEP. The lack of pruritus and presence of fever brings up the possibility of a severe delayed reaction (like DRESS of SJS), but the chance a patient, especially one this age, would have this occur with 2 different structurally unrelated antibiotics is just about impossible. Most likely these reactions are somehow T cell related, but not severe life-threatening.
Re-challenge is ultimately the only method of determining whether she is able to tolerate them. I would hold off on doing that until she needs an antibiotic in this case. Also, although all the data on cross-reactivity between penicillins and cephalosporins are limited to IgE-mediated reactions (and it is very low), I would feel very comfortable giving her cephalosporins. Macrolides are also an option for future treatment. Of course, it is not clear whether clindamycin or Bactrim caused the second reaction, but the odds are greatly in favor of it being the sulfa.