Can linezolid be given to a lactating (breastfeeding) woman?

Linezolid Use During Lactation

Linezolid can be given during lactation with caution, as it is excreted into breast milk in clinically significant amounts, but the estimated infant dose remains below therapeutic pediatric levels and appears relatively safe based on limited available data.

FDA Labeling and Official Guidance

• The FDA label explicitly states that linezolid and its metabolites are excreted in the milk of lactating rats at concentrations similar to maternal plasma, and it is not known whether linezolid is excreted in human milk 1
• The FDA recommends that "caution should be exercised when linezolid is administered to a nursing woman" 1
• No formal guidelines from major societies (AAP, ACOG, Association of Anaesthetists) specifically address linezolid use during lactation in the provided evidence

Clinical Evidence on Milk Transfer

• A case study documented that linezolid transfers into breast milk with a relative infant dose of 15.61% at steady state (day 14 of therapy), which exceeds the typical 10% safety threshold used for most medications 2
• However, the estimated infant dose was 1.84 mg/kg/day, which is well below the recommended therapeutic dose given to neonates requiring linezolid treatment 2
• A 2009 review concluded that despite limited information on linezolid, the risk to infants appears relatively low for most antibiotics used to treat MRSA infections, though close monitoring is needed 3

Clinical Decision Algorithm

When linezolid is necessary for maternal MRSA infection:

• Assess severity: Reserve linezolid for serious MRSA infections where alternative antibiotics (clindamycin, trimethoprim-sulfamethoxazole) are contraindicated or ineffective 3
• Consider temporary cessation: If short-term therapy (≤7-10 days), consider pumping and discarding milk during treatment, as the infant in the documented case did not breastfeed during maternal treatment 2
• Monitor infant closely if breastfeeding continues: Watch for signs of bone marrow suppression (pallor, bruising), gastrointestinal disturbances (diarrhea, feeding difficulties), and any unusual symptoms 3
• Limit duration: Use the shortest effective treatment course, as steady-state concentrations increase over time (higher on day 14 versus day 1) 2

Important Caveats

• The relative infant dose of 15.61% is higher than the generally accepted 10% threshold for medication safety during lactation, warranting heightened vigilance 2
• Data on linezolid in lactation is extremely limited, with only one published case report documenting actual milk concentrations 2
• Linezolid can cause serious adverse effects including myelosuppression and peripheral neuropathy in adults, though these have not been reported in breastfed infants 3
• The pharmacokinetic variability in neonates and young infants may affect drug clearance unpredictably 1