10/27/03 Antibiotic desensitization in adults with cystic fibrosisSummaryAllergic reactions to antibiotics occur in up to 30% of patients with cystic fibrosis (CF). Reported allergies to multiple antibiotics are not unusual in this patient population. Repeated antibiotic exposure and immune hyper-responsiveness increase the risk of allergic reactions and may limit antibiotic choice. Burrows et al of the Prince Charles Hospital, in Brisbane, Australia. Reviewed their experience with attempted "desensitization" to suspected antibiotic offenders in 19 CF patients, sometimes involving multiple procedures using different antibiotics in the same patient. In the 71 attempted desensitization procedures in this patient group, 54 were successful (76%). Allergic reactions caused drug cessation in a total of 19 patient/drug combinations (three after initial successful desensitization and full courses of antibiotics). Over 50% of these reactions occurred on day 1. Desensitization failures were more common in patients with well-documented allergic reactions to a specific drug. The author's concluded that antibiotic desensitization allows safe and successful treatment in the ward setting of many but not all patients with previous allergies to an antibiotic. In some patients, symptoms of allergy still occur during the attempted desensitization and result in cessation of the antibiotics. Reference Respirology. 2003; 8:359-64. Editor's Comments These findings are of practical value in giving one an idea of who often one can successfully introduce an antibiotic (mostly beta-lactam type in this study) by use of a "desensitization" (graded dose increases starting with minute doses) regimen. My experience is similar to that reported above in that this "desensitization" approach is more successful when the history of previous drug allergic reactions is not clear-cut (were they really allergic reactions in the past?). I have put the word "desensitization", as used in this report, in quotes because there is little if any convincing evidence that this graded increased dose introduction really turns off allergic reactivity (true immunologic desensitization). Even if the patient tolerates therapeutic doses of the drug involved after the "desensitization" procedure, that does not mean that the same patient can necessarily tolerate repeat treatment with that drug starting with a therapeutic dose given at some time months in the future. Therefore, one would have to go through the "desensitization" procedure again at that time.
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