Evaluation of lamotrigine toxicity reported to poison centers

Background: Lamotrigine is an antiepileptic drug for the treatment of partial and generalized seizures as well as bipolar disorder. Limited published information exists describing the clinical effects of lamotrigine overdose. Objective: To examine the toxicity of exposures to lamotrigine utilizing national poison center data. Methods: Data on single-substance exposures to lamotrigine reported to the American Association of Poison Control Centers Toxic Exposure Surveillance System in 2000 and 2001 were retrospectively analyzed. Results: There were 493 cases that met the inclusion criteria. The majority of exposures occurred within the age groups 20-59 years old (n=198, 40.2%), followed by less than or equal to4 years old (n=173, 35.1%). Overall, the majority of patients (52.1%)exposed to lamotrigine in overdose experienced no toxic clinical effects. The most common clinical effects reported in overdose were drowsiness/lethargy (20.9%), vomiting (11%), nausea (5.1%), ataxia (4.9%), dizziness/vertigo (4.5%), and tachycardia (4.3%). Major clinical effects included coma (n=6), seizures (n=8), and respiratory depression (n=3). Medical outcome was reported as minor in 150 (30.4%), moderate in 73 (14.8%), and major in 13 (2.6%) cases. There were no deaths. Conclusions: These data demonstrate that the majority of patients exposed to lamotrigine in overdose experienced minor or no clinical effects. Although rare, serious effects can also occur.