Dextromethorphan Safety in Breastfeeding
Dextromethorphan is generally considered safe during breastfeeding, with minimal infant exposure through breast milk and a relative infant dose of less than 1% of the maternal dose. 1
Evidence Supporting Safety
The FDA drug label advises breastfeeding mothers to "ask a health professional before use," which reflects a cautious but not prohibitive stance. 2 However, the available pharmacokinetic data provides reassurance about actual infant exposure levels.
Infant Exposure Data
A pharmacokinetic study in 20 lactating women taking a single 30 mg dose of dextromethorphan found that infant exposure was estimated at only 0.33 ± 0.32 μg/kg/day for dextromethorphan and 1.8 ± 1.0 μg/kg/day for its active metabolite dextrorphan. 1
At steady-state dosing (60 mg twice daily), the estimated infant exposure remained low at 0.64 ± 0.22 μg/kg/day for dextromethorphan and 1.23 ± 0.38 μg/kg/day for dextrorphan. 1
The relative infant dose (RID) was calculated to be less than 1%, which is well below the generally accepted safety threshold of 10% for medication use during breastfeeding. 1
Pharmacokinetic Properties
Dextromethorphan and dextrorphan distribute extensively into breast milk, with milk-to-plasma ratios of 1.0 and 1.6 respectively, but the absolute amounts transferred remain clinically insignificant. 1
The dose received by infants via breast milk is generally much smaller than known safe doses of medications given directly to neonates and infants. 3
Important Caveats
Isolated Adverse Event Report
One nursing infant in the pharmacokinetic study developed an erythematous rash during maternal dextromethorphan use, though causality was not definitively established. 1
This single case warrants monitoring infants for potential skin reactions, though it does not contraindicate breastfeeding. 1
General Safety Profile
Dextromethorphan has been used for over 30 years with a reassuring safety profile showing infrequent and usually non-severe adverse reactions. 4
The predominant symptoms when adverse events occur are dose-related and include neurological, cardiovascular, and gastrointestinal disturbances. 4
Clinical Recommendations
Breastfeeding mothers may use dextromethorphan at recommended doses without interrupting nursing. 1
Use the lowest effective dose for the shortest duration necessary to control cough symptoms. 2
Monitor the infant for unusual sedation, irritability, or skin rashes, though these are unlikely at therapeutic maternal doses. 1
Avoid exceeding recommended doses, as the safety profile is dose-dependent. 4
Do not use if taking monoamine oxidase inhibitors (MAOIs), as this represents a significant drug interaction risk regardless of breastfeeding status. 2