The following information addresses potential interactions with formoterol. When formoterol is used in fixed combination with budesonide, glycopyrrolate, or mometasone, consider interactions associated with budesonide, glycopyrrolate, or mometasone.   No formal drug interaction studies performed to date with the fixed-combination preparations.  
Formoterol metabolized in the liver by CYP isoenzymes 2D6, 2C19, 2C9, and 2A6. 
Drugs that Prolong QT Interval
Potential pharmacologic interaction (increased risk of ventricular arrhythmias and possible potentiation of formoterol effects on cardiovascular system). Use extreme caution during concomitant therapy.
Specific Drugs
Drug
Interaction
Comments
Antidepressants, tricyclic
Possible potentiation of formoterol effects on cardiovascular system 
Extreme caution recommended during concomitant therapy  or within 2 weeks following discontinuance of a tricyclic antidepressant
β-Adrenergic blocking agents (including ophthalmic agents)
Potential antagonism of pulmonary effects and production of severe bronchospasm in asthmatic patients 
If concomitant therapy required, consider cautious use of cardioselective β-adrenergic blocking agents 
Corticosteroids
Potential increased risk of hypokalemia
Diuretics, non-potassium-sparing
Potential additive hypokalemia and/or ECG changes, especially when recommended β-agonist dose is exceeded 
Cautious use recommended 
MAO Inhibitors
Possible potentiation of formoterol effects on cardiovascular system 
Extreme caution recommended during concomitant therapy  or within 2 weeks following discontinuance of an MAO inhibitor
Sympathomimetic agents
Potential additive pharmacologic and adverse effects
Caution recommended for concomitant use of formoterol and sympathomimetic agents administered by any route
Xanthine derivatives
Potential increased risk of hypokalemia
 Formoterol drug interactions (more detail)
