Safe use of meropenem in a patient with a possible nonimmediate allergy to imipenem.

Strong data are lacking on the cross-reactivity between individual carbapenems. We describe a 48-year-old woman with ventilator-associated Pseudomonas aeruginosa pneumonia who received an 8-day course of imipenem-cilastatin and experienced a delayed (i.e., nonimmediate) hypersensitivity reaction, evidenced by an extensive erythematous macular morbilliform rash and an increased eosinophil count. Eight days after completion of therapy, the pneumonia returned, and it was decided to avoid using imipenem-cilastatin; she was administered a 14-day course of meropenem. To our knowledge, this is the first report of a nonimmediate hypersensitivity reaction to imipenem-cilastatin without cross-reactivity to meropenem. This suggests that if carbapenem therapy is unavoidable, meropenem may be cautiously administered in patients with a known allergy to imipenem-cilastatin.