Monobactams

Monobactams

Aztreonam is the first member in the class of monobactam antibiotics and the only one currently available. It’s a synthetic monobactam with a narrow spectrum of activity that includes many gram-negative aerobic bacteria.

Pharmacokinetics

After parenteral administration, aztreonam is rapidly and completely absorbed and widely distributed throughout the body. It’smetabolized partially and excreted primarily in urine as un changed drug.

Pharmacodynamics

Aztreonam’s bactericidal activity results from inhibition of bacterial cell-wall synthesis. It binds to the PBP-3 of susceptible gram-negative bacterial cells, inhibiting cell-wall division and resultingin lysis.

Pharmacotherapeutics

Aztreonam is indicated in a range of therapeutic situations.

• It’s effective against a wide variety of gram-negative aerobic or-ganisms, including P. aeruginosa.

• It’s effective against most strains of thefollowing organisms: E. coli, Enterobacter,Klebsiella pneumoniae, K. oxytoca, Proteus mirabilis, Serratia marcescens, H.influenzae, and Citrobacter.

• It’s also used to treat complicated and uncomplicated UTIs, septicemia, and lower respiratory tract, skinand skin-structure, intra-abdominal, and gynecologic infections caused by susceptible gram-negative aerobic bacteria.

It’s usually active against gram-negative aerobic organisms that are resistant to antibiotics hydrolyzed by beta-lactamases. (Beta-lactamase is an enzyme that makes an antibiotic ineffective.)

It can need help

Aztreonam shouldn’t be used alone as empiric therapy (treatment based on clinical experience rather than on medical data) in a seriously ill patient who may have a gram-positive bacterial infec-tion or a mixed aerobic-anaerobic bacterial infection.

Drug interactions

Aztreonam may interact with several other drugs.

§    Synergistic or additive effects occur when aztreonam is used with aminoglycosides or other antibiotics, such as cefoperazone, cefotaxime, clindamycin, and piperacillin.

§    Potent inducers of beta-lactamase production (cefoxitin, imipenem) may inactivate aztreonam. Concomitant use isn’t rec-ommended.

§    Taking aztreonam with clavulanic acid–containing antibiotics may produce synergistic or antagonistic effects, depending on the organism involved. (See Adverse reactions to aztreonam.)