This study presents the case of a 35-year-old breastfeeding mother who delivered her fourth child 5 months previously and was prescribed 100 mg amisulpride twice daily and 250 mg desvenlafaxine in the morning for treatment-resistant depression. Arriving at this regimen took approximately 2 months postbirth. Because she was keen to continue breastfeeding her infant, and published data on the use of amisulpride and desvenlafaxine were very limited, the clinical team sought assistance from the therapeutic drug monitoring laboratory to quantify infant dose-exposure to guide consideration of continuing breastfeeding. A sampling schedule for milk and plasma from mother and plasma from her infant was agreed and drug concentrations were measured by high-performance liquid chromatography. Absolute (theoretic) infant dose (μg/kg/d) was calculated as the product of the average concentration in milk and an assumed milk intake of 0.15 L/kg/day (294 mg/kg/day for desvenlafaxine and 183 mg/kg/day for amisulpride), and relative infant dose was estimated as absolute infant dose expressed as a percentage of the maternal dose in μg/kg/day (7.8% for desvenlafaxine and 6.1% for amisulpride). Consistent with the infant being partially breastfed, the ratio of drug in the infant's plasma to that in mother's plasma was lower at 1.7% for desvenlafaxine and 3.9% for amisulpride. A pediatric assessment of the infant found achievement of expected developmental progress for age and no detectable drug-related adverse effects. Assessing the safety of breastfeeding was difficult because it involved simultaneous use of two drugs for which there was limited previous experience. However, after discussion of the infant dose-exposure data and lack of adverse effects, the mother elected to continue partial breastfeeding for the next few months. The clinical team plans a reassessment of the infant's progress in 3 months.
From the *Pharmacology and Anaesthesiology Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley, Australia; †Department of Psychological Medicine, King Edward Memorial Hospital, Women and Newborn Health Services, Subiaco, Australia; ‡Department of Neonatal Paediatrics, King Edward Memorial Hospital, Women and Newborn Health Services, Subiaco, Australia; §Clinical Pharmacology and Toxicology Laboratory, Path West Laboratory Medicine, Nedlands, Western Australia; and ∥Pharmacy Department, King Edward Memorial Hospital, Women and Newborn Health Services, Subiaco, Western Australia.
Received for publication July 21, 2010; accepted August 20, 2010.
Correspondence: Kenneth F. Ilett, PhD, Pharmacology and Anaesthesiology Unit, M510, School of Medicine and Pharmacology, University of Western Australia, Crawley, 6009, Western Australia (e-mail: Ken.Ilett@uwa.edu.au).