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Zonisamide-induced behavior disorder in two children
1Department of Pediatrics, Urafune Hospital of Yokohama City University School of Medicine, Japan.
Insights
Zonisamide (ZNS) can cause behavior disorders in children, even at low doses. These adverse effects occurred in young patients without prior mental health issues, suggesting a direct link to ZNS treatment.
Area of Science:
- Neuroscience
- Pediatric Neurology
- Clinical Pharmacology
Background:
- Zonisamide (ZNS) is an anticonvulsant medication used to treat epilepsy.
- Previous reports linked ZNS to behavioral and psychotic disorders, but often in patients with complex partial seizures (CPS) on combination therapy (e.g., with phenytoin (PHT)).
- The causal role of ZNS alone in inducing behavioral issues, particularly in younger patients, remained unclear.
Observation:
- Two pediatric patients, a 1-year-old girl and a 3-year-old boy, developed behavioral disorders.
- Neither patient had prior developmental or mental health problems.
- Both patients experienced secondarily generalized motor seizures during ZNS treatment.
Findings:
- The patients exhibited behavioral disorders despite having serum ZNS concentrations within or even below the established therapeutic range (8.8 and 12.3 µg/mL).
- Unlike previous reports, these children did not have CPS or receive combination therapy, isolating ZNS as the likely causative agent.
- This suggests Zonisamide can induce behavioral disturbances independently and at lower-than-expected levels.
Implications:
- Zonisamide may induce behavioral disorders in pediatric patients even at sub-therapeutic or therapeutic serum concentrations.
- Clinicians should monitor for behavioral changes in children treated with ZNS, irrespective of seizure type or concurrent medications.
- These findings highlight the importance of considering ZNS as a potential cause of new-onset behavioral issues in pediatric epilepsy management.
Abstract:
Zonisamide (ZNS)-induced behavior disorders are reported in a 1-year-old girl and a 3-year-old boy. Both patients, who had no previous developmental or mental problems, displayed secondarily generalized motor seizures. Serum concentrations of ZNS were not high, 8.8 and 12.3 micrograms/ml (effective range 10-30 micrograms/ml) respectively. Although many cases of ZNS-related psychotic reactions and/or behavior disorders have been reported, all affected patients had complex partial seizures (CPS) and had received combination therapy with phenytoin (PHT). Thus, whether the disorders were induced only by ZNS, by an interaction between ZNS and PHT, or by CPS could not be determined. In the children reported, however, ZNS clearly induced behavior disorders at plasma ZNS levels within or even below the therapeutic range.