To the Editor: We read with interest the article by Clark et al. (1) on lamotrigine dosing in pregnant patients with bipolar I disorder. The authors report on the use of lamotrigine in eight patients with bipolar disorder, six of whom received concomitant psychotropic drugs including four women who were taking antidepressant drugs. Dosage adjustments of lamotrigine were made in response to hypomanic, manic, or depressive symptoms. It is not clear whether the dosages of concomitant psychotropic drugs remained the same during pregnancy. Of the three women requiring a dosage increase to manage symptoms, two were also taking antidepressants that can increase the recurrence of bipolar mood episodes both during and after pregnancy (2). There are no data suggesting that monitoring serum levels with corresponding adjustments to lamotrigine dosing will protect against antidepressant-led mood instability. Interestingly, the authors did not report a correlation between lamotrigine concentration and scores on rating scales for depression and mania. Thus, the conclusion that women with bipolar disorder who are treated with lamotrigine experience an increase in symptoms as a result of declining concentrations of this drug is not justified.