METHADONE DISTRIBUTION AND EXCRETION INTO BREAST-MILK OF CLIENTS IN AMETHADONE-MAINTENANCE PROGRAM

Aims Methadone is widely used in maintenance programs for opioid-depen dent subjects. The aims of the study were to quantify the distribution and excretion of methadone in human milk during the early postnatal p eriod and to investigate exposure of breast fed infants to the drug. M ethods Blood and milk samples were obtained from 12 breast feeding wom en who were taking methadone in daily doses ranging from 20-80 mg (0.3 -1.14 mg kg(-1)). Blood was also obtained from eight of their infants. Methadone concentration in these samples was quantified by h.p.l.c. T he infants were observed for withdrawal symptoms. Results The mean (95 % CI) milk/plasma ratio was 0.44 (0.24-0.64). Exposure of the infants, calculated assuming an average milk intake of 0.15 l kg(-1) day and a bioavailability of 100% was 17.4 (10.8-24) mu g kg(-1) day(-1). The m ean infant dose expressed as a percentage of the maternal dose was 2.7 9 (2.07-3.51)%. Methadone concentrations in seven infants were below t he limit of detection for the h.p.l.c. assay procedure, while one infa nt had a plasma methadone concentration 6.5 mu g l(-1). Infant exposur e to methadone via human milk was insufficient to prevent the developm ent of a neonatal abstinence syndrome which was seen in seven (64%) in fants. No adverse effects attributable to methadone in milk were seen. Conclusions We conclude that exposure of breast fed infants to methad one taken by their mothers is minimal and that women in methadone main tenance programs should not be discouraged from breast feeding because of this exposure.