The study drug initially will taken as one 50-mg tablet a day, then the dose increased by one tablet each two weeks, to no more than 3 tablets (150 mg) taken twice a day. During this 12-week dose adjustment phase, the participant will be seen in clinic each 4 weeks for tremor assessments and review of health status. In addition, the participant will be contacted by telephone each week. If any symptom occurs suggestive of side effects, the escalation will be stopped or the dose reduced in order to resolve the symptom.