Levalbuterol HFA MDI followed by Racemic albuterol HFA MDI
Drug- Subjects will receive both treatments: (a) levalbuterol HFA MDI; 45 micrograms (16 cumulative doses); followed by (b) racemic albuterol HFA MDI; 90 micrograms (16 cumulative doses)
- Arm #A
- Xopenex HFA MDI, Pirbuterol HFA MDI