Background: Immediate-type hypersensitivity reactions to quinolones are rare. Some reports describe the presence of cross-reactivity among different members of the group, although no predictive pattern has been established. No previous studies confirm or rule out cross-reactivity between levofloxacin and other quinolones. Therefore, a joint study was designed between 2 allergy departments to assess cross-reactivity between levofloxacin and other quinolones.

Material and Methods: We studied 12 patients who had experienced an immediate-type reaction (4 anaphylaxis and 8 urticaria/angioedema) after oral administration of quinolones. The culprit drugs were as follows: ciprofloxacin (5), levofloxacin (4), levofloxacin plus moxifloxacin (1), moxifloxacin (1), and norfloxacin (1). Allergy was confirmed by skin tests and controlled oral challenge tests with different quinolones.
The basophil activation test (BAT) was applied in 6 patients.

Results: The skin tests were positive in 5 patients with levofloxacin (2), moxifloxacin (2), and ofloxacin (2). BAT was negative in all patients (6/6). Most of the ciprofloxacin-reactive patients (4/5) tolerated levofl xacin. Similarly, 3 of 4 levofloxacin-reactive patients tolerated
ciprofloxacin. Patients who reacted to moxifloxacin and norfloxacin tolerated ciprofloxacin and levofloxacin.

Conclusions: Our results suggest that skin testing and BAT do not help to identify the culprit drug or predict cross-reactivity. Oral challenge testing is the only way to confirm tolerance to a quinolone before prescribing it as a safe alternative. Levofloxacin could be a safer alternative in cases of reaction to first-, second-, or fourth-generation quinolones.

Key words: Quinolone allergy. Levofloxacin. Ciprofloxacin. Drug allergy. Cross reactivity. Basophil activation test.