Efficacy of zonisamide in migraineurs with nonresponse to topiramate.

This study investigated another type of carbonic anhydrase inhibitor and antiepileptic drug, zonisamide, in order to evaluate its potential effectiveness for migraine prophylaxis refractory to topiramate, and to assess intolerability to adverse events, paresthesia in particular. This is an open-labeled retrospective single center study. We included headache patients who met the requirement of migraine without aura and were refractory to topiramate. Patients were treated only with zonisamide 100 mg/day, directly switching from topiramate. Patients were monitored every month for three months. A positive response to treatment (responders) was defined as a 50% or greater reduction in headache days at three months after study commencement, compared with baseline. One hundred and twenty migraineurs who were refractory to topiramate were recruited. Compared with baseline, headache days with zonisamide showed a decrease, compared with baseline (P < 0.01). Two patients complained of adverse effects, such as paresthesia. These results suggest that zonisamide is effective for migraine prophylaxis refractory to topiramate, or intolerable patients due to topiramate-induced paresthesia.