Isolated severe thrombocytopenia and bleeding caused by piperacillin.

Bleeding and severe thrombocytopenia developed in a 71-year-old man who had been receiving piperacillin 5 g intravenously every 8 h for 9 days for the treatment of Pseudomonas aeruginosa septicemia. After piperacillin was discontinued, the platelet counts became normal. Rechallenge was made with 2 g of piperacillin intravenously resulting in thrombocytopenia within 6 h of piperacillin administration. The platelet count normalized after 3 days when no further piperacillin was given.