Lamotrigine (LTG) in Pregnancy: Dosage and Serum Concentration

(1) Ideally obtain total serum LTG level at therapeutic dose before pregnancy. 

(2) If patient is seen during pregnancy: obtain levels as early as possible during pregnancy. 

(3) Frequency during pregnancy: Obtain serum LTG levels Q 4 weeks.

(4) Serum LTG level will mostly fall from first trimester to third trimester.

Both LTG total and free clearance increased throughout pregnancy with a peak of 94% (total) and 89% (free) in the third trimester. This results in decrease in LTG level.

(5) When the LTG plasma concentration falls below the pre-pregnancy/baseline level: Increase the dose of LTG by 20-25% to maintain the target level or to reduce the symptoms.

LTG dosing in bipolar disorder is typically guided by clinical response.

Have low threshold to increase the dose if patient is showing signs of clinical deterioration.

(6) If this dose increase is done during pregnancy: LTG dose should be reduced by 20-25% immediately after delivery. 

(7) Begin this LTG taper within 3 days of delivery: because rapid increase in LTG can occur 3 days- 2 weeks after delivery. 

(8) Frequency after delivery: Obtain serum LTG level Q1-2 weeks. 

(9) Adjust the LTG dose till you reach pre-pregnancy LTG level. 

(10) Monitor mother for LTG toxicity symptoms: ataxia, blurry or double vision, nausea, and dizziness.

(11) LTG is excreted in considerable amounts in breast milk. The dose to the infant can be estimated to >/= 0.2-1 mg/kg/day 2-3 weeks postpartum. Note that the LTG milk/plasma ratio is highly variable.

This in combination with a slow elimination in the infants, may result in LTG plasma concentrations comparable to what is reported during active LTG therapy. 

LTG exposure during lactation is considerably less than placental transfer.



  1. Am J Psychiatry. 2013 Nov 1; 170(11): 1240–1247.
  2. Acta Neurol Scand. 2012 Jul;126(1):e1-4.
  3. Epilepsia. 2000 Jun;41(6):709-13.
  4. Pediatrics. 2008 Jul;122(1):e223-31.
  5. Neurology. 2009 Jul 14; 73(2): 142–149.
  6. J Clin Psychopharmacol. 2014 Apr; 34(2): 244–255.

Please do post your questions or comments below. 

Dr. Harvinder Singh, M.D. (Admin)

Subscribe to Physician’s Guide for Clinical Psychiatry Course for detailed access to 225+ chapters:

Course Details:

Related Articles