Aztreonam !

An injectable or inhaled monobactam for aerobic gram-negative infections, useful in patients with severe allergy to other β-lactams.

Updated 2026-11-01

Class: Monobactams
Enzyme: Penicillin-binding protein 3 of gram-negative bacteria
ATC code: J01DF01

Penicillin-binding protein 3 of gram-negative bacteriaAztreonam

The figure shows aztreonam bound to penicillin-binding protein 3 of Pseudomonas aeruginosa.

Target in 3D: Penicillin-binding protein 3 of gram-negative bacteria. PDB structure 3PBS (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Aztreonam acylates penicillin-binding proteins of gram-negative bacilli (the figure shows PBP3) and blocks cell-wall synthesis, so the bacteria lyse. Its activity against Enterobacterales and Pseudomonas aeruginosa resembles that of ceftazidime; it has no useful activity against gram-positive bacteria or anaerobes.

Crosses the gram-negative outer membrane
Acylates the PBPs of gram-negative bacilli
Cell-wall synthesis stops and the bacteria lyse

Pharmacokinetics

Absorption: Intravenous, intramuscular or inhaled.
Distribution: About half bound to serum proteins; crosses the placenta.
Elimination: Mostly unchanged in the urine.
Half-life: About 1.7 hours with normal kidney function; longer in older adults and kidney failure.

Indications

Urinary tract infections, including pyelonephritis, by susceptible gram-negatives. Acute pyelonephritis →
Lower respiratory tract infections, including pneumonia by Pseudomonas and Enterobacterales. Hospital-acquired and ventilator-associated pneumonia →
Septicemia by gram-negative bacilli. Sepsis and septic shock →
Intra-abdominal infections, including peritonitis, with an anti-anaerobe drug. Peritonitis →
Inhaled, to reduce Pseudomonas exacerbations in cystic fibrosis. Cystic fibrosis →

Adverse effects

Common

Phlebitis or discomfort at the injection site
Rash, diarrhoea, nausea

Contraindications

Known hypersensitivity to aztreonam or any component
Caution (not absolute) in allergy to ceftazidime or other β-lactams

Key interactions

Aminoglycosides: Synergy against Pseudomonas and other gram-negatives; kidney function and hearing are monitored because of the aminoglycoside.
Avibactam (alone or with ceftazidime): Protects aztreonam from ESBL and KPC enzymes in metallo-β-lactamase producers.

What is monitored

Kidney function (to adjust the regimen)
Liver tests in long courses and in children
Signs of allergy in patients with prior β-lactam reactions

Administration and safety

IV infusion, slow IV injection or deep IM injection after reconstitution.
Inhaled aztreonam is a different product given with its own nebulizer; it is never injected.

Nursing care

Clarify the type of previous β-lactam reaction and any ceftazidime allergy.
Watch for rash or wheeze during the first doses.
Remember gram-positive and anaerobic coverage must come from other drugs.
Teaching: report rash, diarrhoea, yellow skin or breathing problems.

Pregnancy and breastfeeding

Aztreonam crosses the placenta; animal studies showed no harm, but human data are limited, so it is used only if clearly needed.

Test yourself

Think of the answer, then tap the question to see it.

With which cephalosporin can aztreonam cross-react, and why?

Ceftazidime, because the two share a similar side chain.

An abdominal infection is treated with aztreonam alone. What coverage is missing?

Anaerobes (such as Bacteroides fragilis) and gram-positives; another drug, for example metronidazole, is added.

Why is aztreonam paired with avibactam against metallo-β-lactamase producers?

Metallo-β-lactamases do not destroy aztreonam, but these bacteria often also carry ESBL or KPC, which avibactam blocks.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - AZTREONAM injection, powder, lyophilized, for solution (DailyMed (U.S. National Library of Medicine), 2026); Aztreonam Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 58 (McGraw Hill, 2023); RCSB PDB - 3PBS: Crystal structure of PBP3 complexed with aztreonam (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.