Zonisamide in managing impulse control disorders in Parkinson's disease

Impulse control disorders (ICDs) are a set of behaviours that take place in a subgroup of patients with Parkinson's disease (PD). Although reduction or switch of dopamine agonists or decrease of levodopa are the common treatment, this does not always improve the compulsive behaviour. Zonisamide (ZNS) has proved effective for motor symptoms in PD and it may be also useful in the field of ICDs. The aim of our study is to evaluate the safety and efficacy of ZNS in PD patients with ICDs who did not improve following a reduction of either levodopa or dopamine agonists. Fifteen patients were initiated on 25 mg/day ZNS dosage, which was titrated to 200 mg/day, as tolerated. Severity of the behaviours was assessed by means of the Clinical Global Impression and the Barratt Impulsiveness Scale, while motor impairment was assessed by means of the Unified Parkinson's Disease Rating Scale (UPDRS). Demographic data, medication dose, treatment duration and adverse events were also collected and analyzed. There was a marked reduction in the severity of impulsive behaviours and global impulsiveness (mean change from baseline -5.8 to -4.8, respectively). UPDRS changed only marginally. ZNS was generally well tolerated. Our study suggests that ZNS may be effective for ICDs in PD. The lack of studies with other medications to treat these behaviours in PD and the potential beneficial effects of ZNS for motor complications make this drug important in the treatment of the disease.