Delirium Associated With Lamotrigine and Fluoxetine Treatment

“Ms. A” was a 35-year-old married, employed, Caucasian woman who had been treated for depression with fluoxetine (40 mg) over the past 5 years. She had no history of confusion, psychosis, or suicidality. Two months prior to admission to our intensive care unit, her psychiatrist added lamotrigine to her medication regimen to treat a mood instability characterized as a bipolar spectrum disorder, although she did not have bipolar I disorder. Her lamotrigine had been increased from 200 mg to 400 mg daily within the 2 weeks prior to her admission. During this time, she developed confusion associated with visual and auditory hallucinations. She also developed the belief that her medications were prenatal vitamins, although she was not pregnant. Consequently, she ingested 200 mg of fluoxetine and 2800 mg of lamotrigine. At admission, her urine toxicology and blood alcohol tests were negative, and there was no other medical evidence to explain her delirium. Her family members corroborated her history that the confusion was completely out of character, and there was no evidence of suicidality to suggest an intentional overdose. Ms. A’s delirium resolved on the second hospital day after she discontinued both medications. She displayed a euthymic mood with a good sense of humor, and there was no further evidence of confusion or hallucinations.