A breastfeeding mother on antiepileptic therapy asks which drug may accumulate in a breastfed infant due to slower metabolism. Which drug is it?

• A. Lamotrigine
• B. Levetiracetam
• C. Gabapentin
• D. Topiramate

Answer: (A)

When a mother breastfeeds, what determines whether a drug will accumulate in the infant is how the baby's body metabolizes and clears that drug. Lamotrigine is mainly cleared by the liver through glucuronidation. In newborns and young infants, the glucuronidation system (UGT enzymes) is immature, so lamotrigine clearance is reduced and the drug can stay in the infant’s circulation longer. Because lamotrigine is secreted into breast milk, this slower infant metabolism can lead to accumulation over time.

The other drugs listed are cleared differently. Levetiracetam, gabapentin, and topiramate are largely excreted renally with limited hepatic metabolism, so their clearance in the infant relies more on kidney function than on immature liver enzymes. While they can be present in breast milk, the issue of slowed hepatic metabolism driving infant accumulation is less central for these agents.

In short, lamotrigine’s reliance on hepatic glucuronidation and the infant’s immature glucuronidation capacity make accumulation in breastfed infants more likely compared with the other options.