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Colistimethate use while Breastfeeding

Medically reviewed by Last updated on Jan 9, 2024.

Drugs containing Colistimethate: Coly Mycin M

Colistimethate Levels and Effects while Breastfeeding

Summary of Use during Lactation

Limited data indicate that colistin is minimally excreted into breastmilk following intramuscular administration of colistimethate. Because colistin is poorly absorbed orally, it is unlikely to be absorbed in appreciable amounts by the infant or adversely affect the breastfed infant. However, no studies have evaluated serum levels or adverse effects in breastfed infants whose mothers were receiving colistimethate. Breastfeeding is acceptable with the use of inhaled colistin or colistimethate.

Drug Levels

Maternal Levels. A single dose of colistimethate equal to 33 mg of colistin was given intramuscularly to 9 women and milk levels were measured once in each women over the next 3 hours. Milk concentrations were 740 mcg/L at 1 hour (n = 1), 760 mcg/L at 2 hours (n = 3) and 140 mcg/L at 3 hours (n = 5) after the dose. Another 20 women were given single intramuscular doses equivalent to 66 mg of colistin. Milk concentrations averaged 500 mcg/L (range 160 to 1100 mcg/L) at 1 hour after the dose, and 789 mcg/L at 2 hours after the dose (range 0 to 2100 mcg/L).[1]

Colistimethate was given to 15 women intramuscularly on day 5 postpartum in a dose equivalent to 66 mg of colistin. After 2 doses, the average peak level was 165 mcg/L and trough was 50 mcg/L. Another 5 women were given a dose equivalent to 132 mg of colistin intramuscularly on day 5 postpartum. After 2 doses, the average peak level was 215 mcg/L and trough was 50 mcg/L. With both doses, peak milk levels occurred 5 hours after the dose.[2]

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.

Effects on Lactation and Breastmilk

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

Alternate Drugs to Consider

Amikacin, Gentamicin, Imipenem and Cilastatin, Tobramycin


Moiraghi A, Moiraghi P. Colistin in organic fluids. In, Herold M, Gabriel Z, eds. Antibiotics: advances in research, production and clinical use; proceedings of the Congress on Antibiotics held in Prague, 15-19 June, 1964. London. Butterworths. 1966;188-92.
Borderon E, Soutoul JH et al. [Excretion of antibiotics in human milk]. Med Mal Infect. 1975;5:373-6.

Substance Identification

Substance Name


CAS Registry Number


Drug Class

  • Breast Feeding
  • Lactation
  • Anti-Infective Agents
  • Antibacterial Agents
  • Polymyxins

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Further information

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