Piperacillin-Tazobactam Hypersensitivity: A Large, Multicenter Analysis.

Background: Piperacillin/tazobactam is a broad-spectrum penicillin. Hypersensitivity reactions are less commonly reported than with other penicillins except in patients with cystic fibrosis.

Objective: Detailed clinical characterization of a patient cohort referred with suspected piperacillin-tazobactam hypersensitivity.

Methods: Retrospective analysis of the demographic characteristics, clinical presentation, investigation, and management of 87 patients presenting to 5 European allergy centers. Patients underwent skin prick and intradermal testing with piperacillin/tazobactam, major (penicilloyl-polylysine) and minor (sodium penilloate) determinants, amoxicillin, benzylpenicillin, flucloxacillin, co-amoxiclav, clavulanic acid, and meropenem with immediate and, where appropriate, delayed reading of tests. Skin test-negative patients underwent drug provocation to piperacillin/tazobactam and/or other penicillins. A multistep protocol was used, depending on risk assessment.

Results: Forty-eight of 87 (55%) patients were diagnosed with hypersensitivity to piperacillin/tazobactam with either positive skin or drug provocation test results, of whom 10 (21%) had a diagnosis of cystic fibrosis. Twenty-six (54%) patients presented with immediate and 22 (45%) with nonimmediate hypersensitivity. Patients with cystic fibrosis predominantly presented with nonimmediate hypersensitivity (70%). Reactions were severe in 52% of immediate reactors (Brown's anaphylaxis grade 3) and moderately severe (systemic involvement) in 75% of nonimmediate reactors. The number of patients with negative skin test results tolerating reintroduction was comparable in immediate (80%) and nonimmediate (88%) hypersensitivity. One-third of patients were cross-sensitized to other penicillins. The cross-sensitization pattern raised the possibility of tazobactam allergy in 3 patients. In 21 patients selectively sensitized to piperacillin/tazobactam (12 immediate, 9 nonimmediate), tolerance to other beta-lactams was demonstrated by drug provocation testing.

Conclusions: Piperacillin-tazobactam caused immediate and nonimmediate hypersensitivity with similar frequency. Most patients were selectively sensitized and tolerated other penicillins. Some patients may be allergic to the beta-lactamase inhibitor only.