Merck Manual

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Brian J. Werth

, PharmD, University of Washington School of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
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Aztreonam is the only antibiotic in an antibiotic class called monobactams, which are a subclass of beta-lactam antibiotics (antibiotics that have a chemical structure called a beta-lactam ring). Beta-lactam antibiotics also include carbapenems, cephalosporins, and penicillins.

Aztreonam is commonly used to treat people who are allergic to some beta-lactam antibiotics and is used in combination with other antibiotics to treat certain antibiotic-resistant bacteria.

Most bacteria have an outer covering (cell wall) that protects them. Like the other beta-lactam antibiotics, aztreonam works by preventing bacteria from forming this cell wall, resulting in death of the bacteria.



Common Uses

Some Side Effects


Infections caused by gram-negative bacteria

Injection site discomfort and swelling

Diarrhea, nausea, vomiting, or a combination


Can typically be used in people allergic to other beta-lactam antibiotics, such as penicillins, cephalosporins, and carbapenems, but should be avoided in people with severe allergies to ceftazidime or cefiderocol

Must be given by injection

Use of Aztreonam During Pregnancy and Breastfeeding

Aztreonam should be taken during pregnancy only when the benefits of treatment outweigh the risks. No harmful effects on the fetus have been observed in animal studies, but no well-designed studies have been done in pregnant women. (See also Drug Use During Pregnancy.)

Use of aztreonam during breastfeeding is generally considered acceptable. (See also Drug Use During Breastfeeding.)

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