Aztreonam.

Aztreonam is a new, totally synthetic beta-lactamase agent--the first monobactam. It is highly resistant to hydrolytic inactivation caused by plasmid-mediated (except PSE-2 enzyme found in some Pseudomonas species) or chromosomally mediated beta-lactamases (except for K1 produced by rare strains of Klebsiella oxytoca). Accordingly, aztreonam remains active against many pathogens that are resistant to other beta-lactam antibiotics. The drug exhibits directed antibacterial activity against gram-negative organisms and is effective as monotherapy against most Enterobacteriaceae and Hemophilus and Neisseria species, including beta-lactamase-producing strains; it is not active against anaerobes or gram-positive organisms. Before culture results are known, it may be necessary to administer the agent empirically in combination with other antibiotics. Aztreonam is rapidly distributed to most body tissues and fluids when administered parenterally. Its serum half-life is 1.7 hours, suggesting a dosing interval of 6-8 hours for severe or life-threatening infections and 8-12 hours for moderately severe infections and urinary tract infections. It is primarily eliminated unchanged in the urine and in much lesser amounts as a microbiologically inactive metabolite; slight biliary excretion may occur. Aztreonam is well-tolerated, lacking any serious adverse hematologic, otic, or renal system effects. Its lack of effect on anaerobes helps to maintain resistance against colonization. Particularly in light of its safety and unique properties, aztreonam promises to be a useful alternative to aminoglycoside therapy.