Antiepileptic drug dose adjustment and monitoring during pregnancy

Serum concentrations of some antiepileptic drugs fall during pregnancy. The dose of lamotrigine may need to be increased. Before conception, or as early as possible in pregnancy, measure the serum concentration of lamotrigine to establish a baseline. Measure the serum lamotrigine concentration at least every 2 months during pregnancy and adjust the dose so the serum concentration stays near the baseline value. After childbirth, maternal lamotrigine kinetics return to normal in 2 to 3 weeks.

Phenytoin and carbamazepine serum concentrations can also fall during pregnancy, and baseline and serial measurements may be used to adjust the dosage. Although levetiracetam serum concentration may fall significantly, measurement is not widely available.