Monobactams are parenteral beta-lactam bactericidal antibiotics.
Aztreonam is currently the only available monobactam. Aztreonam has activity similar to that of ceftazidime against
Enterobacterales that do not produce AmpC beta-lactamase, extended-spectrum beta-lactamase (ESBL), or Klebsiella pneumoniae carbapenemase (KPC)
Aztreonam is not active against anaerobes. Gram-positive bacteria are resistant to aztreonam (in contrast to cephalosporins). Aztreonam acts synergistically with aminoglycosides.
Aztreonam shares structural similarities with few other beta-lactams, making cross-hypersensitivity unlikely, except with ceftazidime and cefiderocol, which have similar R1 side chains. Thus, aztreonam is used mainly for severe aerobic gram-negative bacillary infections (including meningitis) in patients who have a serious beta-lactam allergy but who nevertheless require beta-lactam therapy. Aztreonam is also not labile to metallo-beta-lactamases and can therefore be useful for some infections in which resistance to other beta-lactam antibiotics is mediated by that enzyme.
Other antibiotics are added to cover any suspected gram-positive species or anaerobes.
The dose of aztreonam is reduced in renal failure.