Xopenex is beta-2 adrenergic agonist and Pulmicort is corticosteroid, although they are often combined in clinical practice, the concomitant use of beta-2 adrenergic agonists and corticosteroids may result in additive hypokalemic effects. Since beta-2 agonists can sometimes cause
QT interval
prolongation, the development of hypokalemia may potentiate the risk of ventricular arrhythmias including torsade de pointes. However, clinical data are limited, and the potential significance is unknown.