Ethosuximide for Essential Tremor: An Open-Label Trial

BACKGROUND: T-type calcium channel activation has been postulated to underlie rhythmicity in the olivo-cerebellar system that is implicated in ET. Ethosuximide reduces T-type calcium currents and can suppress tremor in two animal models of ET. We explored the effects of ethosuximide in subjects with ET in an open-label trial using both clinical scales and accelerometric recordings measures. We initially planned to conduct the trial with 15 patients, but due to lack of efficacy and a high incidence of adverse effects, the trial was stopped after seven patients had participated. METHODS: Seven patients diagnosed with ET were included in the study. The ethosuximide dose was 500 mg daily (BID). The main outcome measures were: 1) tremor clinical rating scale (TCRS) score, 2) accelerometric recordings, and 3) self-reported disability scale score. RESULTS: Five patients completed the study, and two dropped out due to adverse effects. There were no significant changes in clinical scores in motor task performance (TCRS 1+2), daily living activities (TCRS 3), or in the patients’ subjective assessment (TCRS 4) and global appraisal. There were no differences observed for accelerometry data or disability scale scores. Anxiety, nervousness, headache, and dizziness were reported by two patients while on ethosuximide, causing them to stop the trial. No patient preferred to continue ethosuximide treatment. DISCUSSION: The results of our exploratory study suggest that ethosuximide is not an effective treatment for ET.