The following information addresses potential interactions with mometasone.   No formal drug interactions studies performed to date using mometasone/formoterol. When the fixed combination used, also consider interactions associated with formoterol.
Mometasone metabolized by CYP3A4 isoenzyme.  
Drugs Affecting Hepatic Microsomal Enzymes
Potent inhibitors of CYP3A4: Potential pharmacokinetic interaction (increased plasma mometasone concentrations).  
Specific Drugs
Drug
Interaction
Comments
Antifungals, azoles (itraconazole, ketoconazole)
Increased mometasone concentrations and the potential for adverse systemic corticosteroid effects  
Use with caution; if concomitant use necessary, monitor for adverse systemic corticosteroid effects  
Antiretrovirals, HIV protease inhibitors (atazanavir, indinavir, nelfinavir, ritonavir, saquinavir)
Increased mometasone concentrations and the potential for adverse systemic corticosteroid effects  
Use with caution; if concomitant use necessary, monitor for adverse systemic corticosteroid effects  
Cobicistat-containing preparations
Increased mometasone concentrations and the potential for adverse systemic corticosteroid effects  
Use with caution; if concomitant use necessary, monitor for adverse systemic corticosteroid effects  
Macrolides (clarithromycin)
Increased mometasone concentrations and the potential for adverse systemic corticosteroid effects  
Use with caution; if concomitant use necessary, monitor for adverse systemic corticosteroid effects   
Nefazodone
Increased mometasone concentrations and the potential for adverse systemic corticosteroid effects  
Use with caution; if concomitant use necessary, monitor for adverse systemic corticosteroid effects  
 Mometasone drug interactions (more detail)
