Immediate Hypersensitivity to Moxifloxacin with Tolerance to Ciprofloxacin: Report of Three Cases and Review of the Literature

Objective To report 3 cases of immediate hypersensitivity reactions to moxifloxacin in patients who tolerated ciprofloxacin. Case summaries A 71-year-old man, a 44-year-old woman, and a 70-year-old woman with a history of a moxifloxacin reaction developed an immediate hypersensitivity reaction upon oral challenge with moxifloxacin in our Drug Safety Clinic. The reaction was mainly characterized by pruritus and urticaria, although dyspnea and hypotension were noted in the first and second patient, respectively. Two of the patients had negative oral challenge tests with ciprofloxacin and all 3 patients tolerated full treatment courses of oral ciprofloxacin. In all 3 cases, use of the Naranjo probability scale indicated a highly probable adverse drug reaction. Discussion Moxiffoxacin, similar to other fluoroquinolones, can cause immediate hypersensitivity reactions. Previous publications have reported both cross-reactivity and a lack of cross-reactivity among various fluoroquinolones. The 3 patients discussed demonstrated a lack of cross-reactivity between moxifloxacin and ciprofloxacin since they tolerated oral challenge tests and full treatment courses of ciprofloxacin. Moxifloxacin has unique side chains at positions 7 and 8 on its bicyclic ring structure. Antigenic specificity to particular side chains at positions 7 and 8 on the bicyclic ring structure of moxifloxacin may explain this lack of cross-reactivity. Higher reporting rates of anaphylaxis to moxifloxacin compared to other fluoroquinolones may also be related to side chain specificity, although definitive evidence for this is lacking. Conclusions Based on our experience, patients who develop immediate hypersensitivity reactions to moxifloxacin may receive ciprofloxacin therapy in an appropriately monitored setting if they have previously tolerated full treatment courses of ciprofloxacin. Research into whether there is a specific side chain reaction unique to moxifloxacin is warranted.