<qa>  What is the class I antiarrhythmic?- If subject is currently receiving a tricyclic antidepressant, anticonvulsant, andor Class I antiarrhythmic e.g., amitriptyline, mexiletine, phenytoin, gabapentin or carbamazepine for treatment of pain or any other condition, subject must be willing and able to maintain stable doses of these agents within 4 weeks prior to randomization and throughout the study i.e., doses cannot be increased or decreased during this period. 