Zonisamide is an
antiepileptic drug widely used to treat
seizures worldwide. In addition to
epilepsy,
zonisamide may have beneficial efficacy in various neurological or
psychiatric diseases. This article reviews the structure, mechanism of action, pharmacokinetics and possible antiparkinsonian action of
zonisamide. A multicentered, randomized, double-blind, placebo-controlled study conducted in Japan provided data suggesting that
zonisamide, as an add-on treatment, has efficacy in treating motor symptoms in patients with
Parkinson's disease (PD).
Zonisamide may be effective in reducing the duration of 'off' time in patients with PD treated with
L-DOPA. The therapeutic doses of
zonisamide for the treatment of PD are 50-100 mg/day, considerably lower than those for the treatment of
epilepsy (200-400 mg/day). It is expected that
zonisamide will be safe and tolerated in patients with PD, as it has been used as an
antiepileptic for more than 15 years; however, further studies are required to evaluate its safety and tolerability in the treatment of PD. The pharmacological mechanisms of the beneficial actions of
zonisamide in PD remain unclear. Various hypotheses have been proposed, but the supporting data are not yet sufficient to draw any conclusions. Further basic research is required to advance our understanding of the antiparkinsonian mechanism of
zonisamide.