U.S. flag

An official website of the United States government

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-.

Cover of Drugs and Lactation Database (LactMed)

Drugs and Lactation Database (LactMed) [Internet].

Show details

Nalidixic Acid

Last Revision: August 16, 2021.

Estimated reading time: 1 minute

CASRN: 389-08-2

image 134975483 in the ncbi pubchem database

Drug Levels and Effects

Summary of Use during Lactation

Limited information indicates that maternal doses of nalidixic acid up to 2 grams daily produce low levels in milk and would usually not be expected to cause any adverse effects in breastfed infants with monitoring of the infant for possible effects on the gastrointestinal flora, such as diarrhea or candidiasis (thrush, diaper rash). Nalidixic acid should be avoided while breastfeeding a glucose-6-phosphate dehydrogenase (G6PD) deficient infant. Other agents are preferred, especially while nursing a newborn or preterm infant.

Drug Levels

Maternal Levels. One paper reported old, unpublished data obtained from the manufacturer in which a breastmilk concentration of 2 mg/L was found at an unspecified time in 4 women taking nalidixic acid 1 gram orally 4 times daily.[1]

Thirteen lactating women were given 2 grams of nalidixic acid as a single dose between the third and eighth day postpartum. The average concentration of nalidixic acid in milk during the first four-hour collection period was 0.64 mg/L (range 0.3 to 1.1 mg/L); concentration in milk from other collection periods were as follows: 0.43 mg/L at 4 to 7 hours; 0.2 mg/L at 7 to 10.5 hours; 0.1 mg/L at 10.5 to 16 hours and 0.02 mg/L at 16 to 24 hours after the dose. Using the peak milk level data from this study, the authors estimated that an exclusively breastfed infant would receive a maximum of 300 mcg daily with this maternal dosage regimen, or less than 0.3% of an infant dose.[2]

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

Effects in Breastfed Infants

Decreased weight gain, pallor, jaundice occurred in a 16-day-old infant probably caused by hemolytic anemia induced by maternal use of nalidixic acid orally 1 gram four times daily and amobarbital 65 mg orally three times daily. The infant developed jaundice, hyperbilirubinemia, reticulocytosis, eosinophilia, Heinz bodies and other signs of hemolysis 7 days after its mother was started on nalidixic acid. No G-6-PD deficiency or hemoglobin Zurich could be demonstrated.[1]

Effects on Lactation and Breastmilk

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


Belton EM, Jones RV. Haemolytic anaemia due to nalidixic acid. Lancet 1965;286:691. Letter. PMID: 4158226. [PubMed: 4158226]
Traeger A, Peiker G. Excretion of nalidixic acid via mother's milk. Arch Toxicol Suppl. 1980;4:388–90. [PubMed: 6933944]

Substance Identification

Substance Name

Nalidixic Acid

CAS Registry Number


Drug Class

Breast Feeding


Anti-Infective Agents, Urinary

Antibacterial Agents


Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.


Related information

Similar articles in PubMed

  • Review Mycophenolate[Drugs and Lactation Database (...]
    Review Mycophenolate
    . Drugs and Lactation Database (LactMed). 2006
  • Review Norfloxacin[Drugs and Lactation Database (...]
    Review Norfloxacin
    . Drugs and Lactation Database (LactMed). 2006
  • Review Enoxacin[Drugs and Lactation Database (...]
    Review Enoxacin
    . Drugs and Lactation Database (LactMed). 2006
  • Review Tranexamic Acid[Drugs and Lactation Database (...]
    Review Tranexamic Acid
    . Drugs and Lactation Database (LactMed). 2006
  • Review Ursodiol[Drugs and Lactation Database (...]
    Review Ursodiol
    . Drugs and Lactation Database (LactMed). 2006
See reviews...See all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...