- Concomitant medications: Participants may be on stable doses of cholinesterase inhibitors for 90 days prior to screening (may not be started during the trial); antidepressant or antipsychotic medications are acceptable if symptoms are controlled and therapy is at stable dosage for at least 30 days prior to screening; vitamin E at 200 IU daily will be provided to all participants beginning at baseline/randomization (higher doses must be discontinued at the screening visit)