Abstract
Codeine (C) is often prescribed for post-partum analgesia. Little is known about C levels in colostrum and neonatal plasma (NP). We measured levels of C and its metabolite morphine (M) in breast milk (BM) and NP. Free C and M were measured by RIA sensitive to 0.5 ng/ml in NP and 2 ng/ml in BM. C dosing, 30 or 60 mg P.O., was determined by each woman's physician. Infants were full term, had 5 min. Apgars≥ 8, and had the following mean values: birth weight = 3.46 kg, age at sampling = 42 hrs., interval from dose to feed = 28 min. Mothers took a mean =4.0 doses of C. BM concentrations of C (ng/ml) and M (ng/ml) in one woman after 60 mg of C were: 71.1 and 8.5 (½hr) 71.1 and 9.1 (1 hr); 199 and 11.2 (2 hr); 126 and 12.7 (4 hr). The rise in BM levels of M over 4 hrs might be explained by the binding affinity of BM for M. NP levels are presented below:
In infants #1 and #2, C and M levels in NP rose over time. This may be due to slow absorption because of the large volume of BM and/or to enterohepatic circulation. The M/C ratio in NP of 0.54 is higher than the ratio in BM at feeding time of 0.15. The increased M/C ratio might be due to metabolism of C to M in neonates or greater conjugation of C than M. NP levels of C and M after a limited exposure are low and are profiably safe.
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Naumburg, E., Meny, R., Findlay, J. et al. CODEINE AND MORPHINE LEVELS IN BREAST MILK AND NEONATAL PLASMA. Pediatr Res 21 (Suppl 4), 240 (1987). https://doi.org/10.1203/00006450-198704010-00437
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DOI: https://doi.org/10.1203/00006450-198704010-00437