Aztreonam-induced myelosuppression during treatment of Pseudomonas aeruginosa pneumonia.

Aztreonam is a synthetic, monobactam antibiotic structurally related to the beta-lactam class of drugs. It has inhibitory activity against many aerobic gram-negative bacteria, although it does not inhibit gram-positive or anaerobic bacteria. Administration of aztreonam occasionally is associated with minimal and transient adverse effects. This case report describes a patient we believe experienced bone marrow suppression approximately ten days after aztreonam was given for treatment of pneumonia caused by Pseudomonas aeruginosa. This untoward effect primarily was manifested as neutropenia, although normochromic, normocytic anemia and thrombocytopenia were noted as well. One week after aztreonam was discontinued, the patient's bone marrow suppression resolved spontaneously. Although the mechanism responsible for myelosuppression is unclear, aztreonam may be implicated as the offending agent based on the temporal relationship between the development of neutropenia and its administration, and the resolution of neutropenia upon its discontinuation.