Cefepime challenge after piperacillin/tazobactam-induced thrombocytopenia.

Drug-induced thrombocytopenia (DITP) has been described as a sudden and severe hematologic complication of piperacillin/tazobactam. The proposed mechanism by which piperacillin/tazobactam causes DITP involves the formation of a covalent bond to platelet membrane protein thereby inducing a humoral immune response. Given the immunogenic nature of this adverse event and the structural similarities across beta-lactam antibiotics, the potential for cross-reactivity between agents within the class should be considered. However, the structural moiety of piperacillin/tazobactam responsible for this immunogenic response has not been identified-the relationship between structure and activity for this phenomenon remains unknown. Data on the safety and cross-reactivity of other beta-lactam agents in this setting is lacking. We report the first case of piperacillin/tazobactam DITP successfully challenged by the use of cefepime for the treatment of aspiration pneumonia. Further studies are needed to determine the structural moiety of piperacillin/tazobactam responsible for this immunogenic response and evaluate the safety of other beta-lactam antibiotics in this clinical setting.