An old man enters the hospital with myocardial infarction and a severe ventricular arrhythmia. The antiarrhythmic drug chosen has a narrow therapeutic window. The minimum toxic plasma concentration is 1.5 times the minimum therapeutic plasma concentration. The half life is 6 hrs. It is essential to maintain the plasma concentration above the minimum therapeutic level to prevent a possible lethal arrhythmia. Of the following, the most appropriate dosing regimen would be
Once a day Twice a day Four times a day Constant intravenous infusion