Abstract
Pipercillin-tazobactam is a frequently used antibiotic that has a broad spectrum of antibacterial activity. The development of severe thrombocytopenia following the use of piperacillin-tazobactam is unusual. Several mechanisms have been proposed for the pathogenesis of thrombocytopenia in this setting which include immune and non-immune causes. Multiple case reports have shown the ability of piperacillin-tazobactam to cause drug-induced immune thrombocytopenia, likely through formation of antibodies that recognize platelets in the presence of soluble piperacillin. However, severe and rapid development of thrombocytopenia that occurs in association with reexposure to piperacillin-tazobactam has not been clearly demonstrated in the literature. We present two cases in whom severe and rapid development of thrombocytopenia has occurred subsequent to administration of piperacillin-tazobactam with a prior history of recent exposure to the drug. In both cases, thrombocytopenia improved immediately and dramatically following withdrawal of piperacillin-tazobactam with initiation of steroids and intravenous immunoglubulins, suggesting and immune related drug-induced thrombocytopenia.