Eye rolling as a manifestation of clobazam toxicity in a child with epilepsy

A four-year-old male with symptomatic generalized epilepsy presented with ataxia, eye rolling, and episodes of back arching which were of non-epileptic origin following the introduction of clobazam at 0.75mg/kg/day. Concurrent antiepileptic medication was lamotrigine at 13mg/kg/day. Clobazam plasma levels were within the normal range, while N-desmethylclobazam (DCLB) concentrations were between five and seven times above the upper limit of the normal range. The plasma elimination half-life for DCLB was prolonged, suggesting a genetic variability in DCLB metabolism leading to toxicity. Reduction in the dose of clobazam to 0.3mg/kg/day was associated with resolution of the non-epileptic neurological symptoms, reduction in DCLB plasma levels, and maintenance of seizure control.