Mechanism of Action
- Although the exact mechanism of action of zonisamide remains unclear, it is suggested that the drug exerts its anticonvulsant effects by blocking the spread or propagation of seizure discharges and by suppressing epileptogenic focus activity.
- Zonisamide, like phenytoin and carbamazepine, selectively prevents tonic extensor convulsions induced by maximal electroshock in mice, rats, rabbits and dogs, and also those induced by pentylenetetrazol in mice.
- Zonisamide strongly suppresses cortical focal seizures induced by electrical stimulation of the visual cortex as well as spike and wave discharges induced by cortical application of conjugated estrogen in cats. Furthermore zonisamide markedly suppresses both spike activites and secondarily generalized seizures induced by cortical application of tungstic acid gel in rats and by cortical freezing in cats.
- Zonisamide reduces the duration of after-discharge and increases the threshold current for generalized convulsions in cortical and hippocampal-kindled rats.
Clinical Studies
The results of clinical studies on the sum of 965 cases including double blind comparative study and comparative study are as shown below.
| Subjects | Improvement rate | |
| Partial epilepsy | monotherapy | 77 % (47/61) |
| add-on therapy, refractory to other anti-epileptics | 39 % (239/620) | |
| Primary generalized epilepsy | monotherapy | 73%(8/11) |
| add-on therapy, refractory to other anti-epileptics | 38 % (12/32) | |
| Secondary generalized epilepsy | monotherapy | 40 % (4/10) |
| Add-on therapy, refractory to other anti-epileptics | 23 % (54/231) | |