Drug Levels and Effects:

Summary of Use during Lactation:

Limited information indicates that single maternal doses of aztreonam of 1 gram produce low levels in milk that are not expected to cause adverse effects in breastfed infants. Occasionally, disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush, has been reported with beta-lactams, but these effects have not been adequately evaluated.

Drug Levels:

Maternal Levels.

After a single intramuscular dose of aztreonam 1 gram in 6 women, peak milk levels averaging 0.3 mg/L occurred 6 hours after the dose. In 6 other women given a single 1 gram dose of aztreonam intravenously, peak milk levels averaged 0.2 mg/L at 2.4 hours after the dose. Aztreoman was detectable (detection limit 0.09 mg/L) in milk between 2 and 8 hours after the intramuscular dose and 1.5 and 8 hours after the intravenous dose.[1][2]

After a single intravenous dose of aztreonam 1 gram, milk levels ranging from 0.4 to 1 mg/L occurred 1 to 5 hours after the dose with little variation in milk levels during this time in each woman. On average, levels were slightly higher 2 hours after the dose, but in individuals the peak level occurred at various times between 1 and 4 hours.[3]

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

Relevant published information was not found as of the revision date.

Possible Effects on Lactation:

Relevant published information was not found as of the revision date.


1. Fleiss PM, Devlin R, Richwald G et al.Aztreonamexcretion in human milk. Clin Pharmacol Ther. 1984;35:240. Abstract.
2. Fleiss PM, Richwald GA, Gordon J et al.Aztreonamin human serum and breast milk. Br J Clin Pharmacol. 1985;19:509-11. PMID:4039600
3. Ito K, Hirose R, Tamaya T et al. Pharmacokinetic and clinical studies of aztreonam in the perinatal period. Jpn J Antibiot. 1990;43:719-26. PMID:2381040

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antiinfective Agents

  • Antibacterial Agents

  • Monobactams

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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