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A dose of CAYSTON consists of a 2 mL amber glass vial containing lyophilized aztreonam (75 mg) and lysine (46.7 mg), and a low-density polyethylene ampule containing 1 mL sterile diluent (0.17% sodium chloride).  The reconstituted solution is for inhalation. The formulation contains no preservatives or arginine.   

The active ingredient in CAYSTON is aztreonam, a monobactam antibacterial. The monobactams are structurally different from beta-lactam antibiotics (e.g., penicillins, cephalosporins, carbapenems) due to a monocyclic nucleus.  This nucleus contains several side chains; sulfonic acid in the 1-position activates the nucleus, an aminothiazolyl oxime side chain in the 3-position confers specificity for aerobic Gram-negative bacteria including Pseudomonas spp., and a methyl group in the 4-position enhances beta-lactamase stability. 

Aztreonam is designated chemically as (Z)-2-[[[(2-amino-4­thiazolyl)[[(2S,3S)-2-methyl-4-oxo-1-sulfo-3­azetidinyl]carbamoyl]methylene]amino]oxy]-2-methylpropionic acid. The structural formula is presented below:

CAYSTON (aztreonam for inhalation solution) is a white to off-white powder.  CAYSTON (aztreonam for inhalation solution) is sterile, hygroscopic, and light sensitive.  Once reconstituted with the supplied diluent, the pH range is 4.5 to 6.0.  

Last reviewed on RxList: 3/11/2010
This monograph has been modified to include the generic and brand name in many instances.