NEW YORK (Reuters Health) – There’s a 25% chance that patients with hypersensitivity to cephalosporins will also react to penicillins, a European group reports, but the risk with other beta-lactams is much smaller.
However, the researchers advise pretreatment skin testing in these situations, in their report in the October 1 online issue of the Journal of Allergy and Clinical Immunology.
Dr. Antonino Romano with the Complesso Integrato Columbus in Rome, Italy, and colleagues point out that several studies have looked at cross-reactivity to cephalosporins in patients with penicillin hypersensitivity, but detailed information about the reverse is patchy.
“We conducted a prospective study to evaluate the possibility of giving penicillins, monobactams, and carbapenems to patients with documented cephalosporin allergy who especially require these treatments,” the authors explain.
To that end, they studied 98 consecutive patients who had had immediate reactions to cephalosporins. All the subjects underwent skin testing with penicillin reagents, aztreonam, imipenem/cilastatin, and meropenem, as well as serum IgE assays specific for penicillin. Those with negative results underwent confirmatory challenges.
Combining the results of skin tests and specific IgE assays with the penicillin reagents, 25 (25.5% ) subjects had positive results to these reagents, the investigators found. Three (3.1%) had positive responses to aztreonam, two (2%) to imipenem/cilastatin, and one (1%) to meropenem.
Looked at another way, 72 (73.5%) patients had negative test results, including challenges, with all beta-lactams other than cephalosporins.
Dr. Romano and colleagues conclude that their results support recommendation on the management of patients with cephalosporin reactions who require a penicillin: skin test first and if negative, treat; if positive, use an alternative antibiotic or undertake penicillin desensitization.
“On the other hand, our data indicate a very low rate of cross-reactivity between cephalosporins and both aztreonam and carbapenems,” they write. “Therefore the practice of avoiding the latter in patients with cephalosporin allergy should be reconsidered.”
IgE-mediated hypersensitivity to cephalosporins: Cross-reactivity and tolerability of penicillins, monobactams, and carbapenems
J Allergy Clin Immunol 2010.