Increased risk of systemic side effects w/ potent CYP 3A4 inhibitors eg, ritonavir, atazanavir, clarithromycin, indinavir, itraconazole, nelfinavir, saquinavir, ketoconazole, telithromycin. May result to ECG changes &/or hypokalemia w/ non-K sparing diuretics eg, loop or thiazide diuretics; xanthine derivatives & glucocorticosteroids. Cardiac tolerance to β2
-sympathomimetics may be impaired w/ levodopa, levothyroxine, oxytocin & alcohol. May precipitate hypertensive reactions w/ MAOIs including w/ similar properties eg, furazolidone & procarbazine. Elevated risk of arrhythmias w/ anaesth w/ halogenated hydrocarbons. Potentially additive effect w/ β-adrenergics. Hypokalemia may increase the risk of arrhythmias w/ digitalis glycosides. May increase the risk of ventricular arrhythmias w/ drugs that prolong QTc interval eg, TCAs, MAOIs, antipsychotics (including phenothiazines), quinidine, disopyramide, procainamide & antihistamines.