HCPCS Level II code J0457 describes a 100 mg injection of aztreonam, an intravenous or intramuscular antibacterial agent used for treatment of susceptible gram-negative infections; the service is typically reported for inpatient or outpatient infusion/injection administration in settings such as hospital inpatient, hospital outpatient, emergency department, or ambulatory infusion centers where parenteral antibiotic therapy is delivered.