- Subjects on the following concomitant medications at the time of Screening are excluded from participating in the study: 1) Calcium antagonists other than amlodipine or felodipine; 2) Flecainide, encainide, propafenone, sotalol, dofetilide or disopyramide; 3) Subjects receiving i.v. positive inotropic agents within seven days of the Screening Visit or Randomization Visit; 4) Subjects receiving a human BNP, including nesiritide, within seven days of the Screening Visit or Randomization Visit; 5) Subjects receiving oral or i.v. type-III PDE inhibitors within seven days of the Screening Visit or Randomization Visit.