Seizures secondary to lamotrigine toxicity in a two-year-old

To report a case of acute pediatric lamotrigine ingestion resulting in seizures.

A 2-year-old boy presented to the emergency department after an acute ingestion of up to 43 mg/kg of lamotrigine. He had 2 generalized seizures, with the first occurring 60 minutes after ingestion. Examination revealed alternate drowsiness and irritability, as well as nystagmus and hyperreflexia. Results of electrocardiogram, blood glucose, complete blood count, urea, electrolytes, and venous blood gas evaluations were all within normal limits. There was a mildly raised lactate level of 3.4 mEq/L (reference range 0.7-2.5). He was given intravenous diazepam 1 mg for irritability. After a 12-hour observation period, the patient was discharged with no further complications.

The Naranjo probability scale in this case suggested a probable causality between the acute lamotrigine ingestion and seizures. This is the lowest acute dose causing pediatric seizure reported in the literature; however, this dose is still significantly higher than a therapeutic dose. A MEDLINE search (1966-January 2010) using the search terms lamotrigine, seizures, toxicity, overdose, ingestion, and pediatric/paediatric, not limited to English-language literature, revealed 5 other cases of seizures in children after lamotrigine ingestion. In all the acute cases, time to first seizure onset ranged from 20 to 60 minutes after ingestion. Two children had gastrointestinal decontamination, both after the onset of seizures. All had full recovery with supportive care.

Lamotrigine has the ability to cause seizures in children from acute single ingestion at a lower dose than previously described. There is not enough information available to establish a toxic dose or dose that requires hospital assessment. Gastrointestinal decontamination should be contraindicated. Supportive care, including administration of benzodiazepines, is appropriate.