Background Selective serotonin reuptake inhibitors are currently the m
ost widely prescribed antidepressant drugs. There are only four publis
hed studies of breast-feeding mothers and their infants in which the m
others were taking fluoxetine. Method Four mothers who took fluoxetine
and their breast-fed infants were studied. Samples of plasma, breast-
milk and urine were taken from the mothers and of plasma and urine fro
m infants for assays of drug and metabolite concentrations. Bayley Sca
les of Infant Development were repeatedly used to assess cognitive and
psychomotor development of the infants. Results Fluoxetine and norflu
oxetine were detected in all samples of maternal plasma (range of tota
l concentration 138-427 ng/ml) and in breast-milk (range 39-177 ng/ml)
. Amounts of both fluoxetine and norfluoxetine in infants' plasma and
urine were below the lower limit of detection. All infants were observ
ed to be developing normally and showed no abnormal findings on neurol
ogical examination. Conclusions Much larger databases are needed but t
hese four cases do not provide any evidence to suggest that women who
are maintained on therapeutic doses of fluoxetine should discontinue b
reast-feeding their infants if they wish to breast-feed.