Codeine
Relative Infant Dose (RID)
1%
✓ Verified
Milk-to-Plasma Ratio (M:P)
1.90
✓ Verified
What This Means
Codeine transfers about 1% of the maternal dose through breast milk. This is generally considered acceptable, but discussing timing of doses with your healthcare provider may be helpful. The M:P ratio of 1.90 means the drug concentrates more in breast milk than in blood, meaning more may reach your baby. Consider discussing timing (e.g., taking after a feeding) with your healthcare provider.
Important: This information is for educational purposes only. Always consult your healthcare provider before taking any medication while breastfeeding. Do not stop prescribed medications without medical advice.
Data source: LactMed NBK501212 (Feb 2026): RID 0.3-1.2% across multiple studies. Single 60mg dose → 1.2% (Findlay et al. 1981); Multiple doses → 0.3-1% (Meny et al. 1993). Note: CYP2D6 ultra-rapid metabolizers can have much higher morphine in milk. • LactCheck by Benevolence Labs