Abstracts

Many women with epilepsy who are planning pregnancy are treated with Lamotrigine (LTG) resulting in greater fetal exposure to the drug. Current care guidelines suggest that mothers with epilepsy breast-feed their children. These recommendations are made without regard to how nursing newborns metabolize medication. Lamictal is extensively metabolized by glucuronidation, which is immature in neonates and may lead to drug accumulation. This paper reports LTG levels in full term nursing newborns born to mothers with epilepsy on Lamictal monotherapy.
Serum LTG levels were obtained in nursing mothers and their neonates on Day 10 of newborn life and at two months when available. Maternal LTG clearance during pregnancy and post-partum was determined and correlated with levels.
Four mothers with partial epilepsy on LTG monotherapy and their newborns were evaluated. Serum LTG levels in nursing newborns ranged from [lt]1.0 to 2.0 mcg/ml on Day 10 of life. Three babies had LTG levels [gt]1.0 mcg/ml. After excluding one child with an undetectable level, the LTG levels in newborns were on average 30% (range 20-43%) of the maternal drug level. No decline was noted in two children with repeat levels at two months.[table1]
Serum concentrations of LTG in breast-fed children were higher than expected, in some cases reaching [quot]therapeutic[quot] ranges. These high levels may be explained by poor neonatal drug elimination due to immature glucuronidation. Our observation that not all newborns had a high LTG level suggests considerable genetic variability in metabolism. Our limited data suggests monitoring blood levels in nursing children and the need for individual counseling for women with epilepsy regarding breast-feeding.