Rationale for combining an anticholinergic agent and a β2-adrenergic receptor agonist
| Different mechanisms of action | |
| Parasympathetic versus sympathetic system | |
| Different sites of action (?) | |
| Proximal versus distal airways | |
| Additive/synergistic effects | |
| Onset and duration of activity | |
| Limitation of dose and side-effects | |
| Improved compliance | |
| Cost-effectiveness |