Oxycodone as a component of multimodal analgesia for lactating mothers after Caesarean section: relationships between maternal plasma, breast milk and neonatal plasma levels.

BACKGROUND

Oxycodone has become popular for post-Caesarean section (CS) analgesia yet it is not currently recommended for use in breast-feeding mothers because of limited information on its excretion into breast milk.

AIM

To investigate the relationship between maternal ingestion of oxycodone after CS and the resultant maternal plasma, breast milk and neonatal plasma drug levels up to 72-h post-partum.

METHODS

Fifty breast-feeding mothers taking oxycodone had blood and breast milk samples analysed for oxycodone levels at 24 h intervals after CS. Forty-one neonates had blood samples taken at 48 h.

RESULTS

Oxycodone was detected in the milk of mothers who had taken any dose in a 24-h period, with significant correlation between maternal plasma and milk levels (R(2) = 0.81). The median milk:plasma (M:P) ratio for the same period was 3.2:1. Over the subsequent 48 h, the relationship between plasma and milk levels was less strong (R(2) = 0.59) and there was a larger range of M:P levels with evidence of persistence of oxycodone in the breast milk of some mothers. Oxycodone levels up to 168 ng/mL were detected in breast milk (20% > 100 ng/mL). Oxycodone was detected in the plasma of one infant.

CONCLUSIONS

Oxycodone is concentrated in human breast milk up to 72-h post-partum. Breastfed infants may receive > 10% of a therapeutic infant dose. However, maternal oxycodone intake up to 72-h post-CS poses only minimal risk to the breast-feeding infant as low volumes of breast milk are ingested during this period.