Paroxetine Levels in Postpartum Depressed Women, Breast Milk, and Infant Serum

Background: The purpose of this study wasto determine the concentrations of paroxetine in maternal serum,breast milk, and infant serum samples and to estimate infantexposure through breastfeeding.

Method: A total of 25 sample sets wasobtained: 1 sample set each from 23 mother-infant dyads and 2sample sets from 1 mother-infant dyad. All mothers met DSM-IVcriteria for major depressive disorder. The maternal fixed dosageof paroxetine was 10, 20, or 40 mg/day for a minimum of 30 daysbefore the samples were drawn. Samples were collected 6 hoursafter dose intake, and the concentration of paroxetine in eachsample was determined using gas chromatography/mass spectrometry.The analytic method employed in this study is the most sensitiveto date, with the ability to detect drug concentrations as low as0.1 ng/mL.

Results: Detectable levels of paroxetinewere present in all maternal serum samples and in 24 of the 25breast milk samples. In all of the infant serum samples, theparoxetine concentrations were below the lower limit ofquantification. No unusual adverse effects were reported in anyof the infants.

Conclusion: The results of this studydemonstrate that paroxetine, like the other selective serotoninreuptake inhibitors studied to date, is excreted into the breastmilk of nursing mothers. The mean infant dose of paroxetine was1.1% of the maternal dose. Although no short-term adverse effectswere reported in any of the infants in this study, future studiesare needed to address a more systematic method for observing andrecording any adverse effects. In addition, future studies shouldincorporate follow-up studies in order to evaluate possiblelong-term effects of paroxetine exposure.