From the Research
For pregnant women with epilepsy on lamotrigine in the third trimester, aim to maintain therapeutic serum levels between 2.5-15 μg/mL, and after doubling the dose, recheck lamotrigine levels within 4 weeks to ensure they're within the therapeutic range, as suggested by the most recent and highest quality study 1.
Key Considerations
- The goal is to maintain seizure control while minimizing the risk of medication side effects and teratogenic effects.
- Lamotrigine clearance increases significantly during pregnancy, especially in the third trimester, due to enhanced hepatic metabolism and renal clearance, which may necessitate dose increases of 50-200% to maintain seizure control 2.
- More frequent monitoring is necessary during pregnancy, with plasma concentration of lamotrigine measured every 4 weeks throughout pregnancy, as recommended by 2.
- After delivery, the dose should be gradually reduced back to pre-pregnancy levels over 2-4 weeks to avoid toxicity, as lamotrigine clearance rapidly returns to normal.
Monitoring and Dose Adjustment
- The dose of lamotrigine should be increased by 20-25% when the plasma concentration falls below the reference concentration, as suggested by 2.
- Recheck lamotrigine levels within 4 weeks after doubling the dose to ensure they're within the therapeutic range, taking into account the medication's half-life and the time it takes to reach steady state 3.
- Monitor for breakthrough seizures and medication side effects such as dizziness, headache, double vision, or rash, and adjust the dose accordingly.