The metabolism of Letrozole can be increased when combined with Rifapentine. The metabolism of Letrozole can be decreased when combined with Ketoconazole. The metabolism of Letrozole can be decreased when combined with Erythromycin. The serum concentration of Letrozole can be increased when it is combined with Fusidic Acid. The metabolism of Letrozole can be decreased when combined with Amiodarone. The metabolism of Letrozole can be decreased when combined with Fosamprenavir. The serum concentration of Letrozole can be increased when it is combined with Netupitant. The metabolism of Letrozole can be decreased when combined with Clotrimazole. Deslanoside may decrease the cardiotoxic activities of Letrozole. The serum concentration of Letrozole can be increased when it is combined with Fosaprepitant. The therapeutic efficacy of Letrozole can be decreased when used in combination with Sarilumab. The metabolism of Letrozole can be decreased when combined with Sulfisoxazole. The metabolism of Letrozole can be decreased when combined with Saquinavir. The serum concentration of Conivaptan can be increased when it is combined with Letrozole. The metabolism of Letrozole can be decreased when combined with Sildenafil. The metabolism of Letrozole can be increased when combined with Rifabutin. The metabolism of Letrozole can be increased when combined with Phenobarbital. Digitoxin may decrease the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be increased when combined with Nevirapine. The metabolism of Letrozole can be decreased when combined with Venlafaxine. The serum concentration of Letrozole can be decreased when it is combined with Mitotane. The metabolism of Letrozole can be decreased when combined with Verapamil. The metabolism of Letrozole can be decreased when combined with Nefazodone. The metabolism of Letrozole can be decreased when combined with Lopinavir. The metabolism of Letrozole can be decreased when combined with Crizotinib. The metabolism of Letrozole can be decreased when combined with Indinavir. The serum concentration of Letrozole can be decreased when it is combined with St. John's Wort. Proscillaridin may decrease the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be decreased when combined with Ranolazine. The metabolism of Letrozole can be decreased when combined with Diltiazem. The metabolism of Letrozole can be decreased when combined with Boceprevir. The metabolism of Letrozole can be decreased when combined with Bortezomib. The risk or severity of adverse effects can be increased when Paclitaxel is combined with Letrozole. The metabolism of Letrozole can be decreased when combined with Voriconazole. The metabolism of Letrozole can be decreased when combined with Idelalisib. The metabolism of Letrozole can be increased when combined with Rifampicin. The serum concentration of Letrozole can be decreased when it is combined with Bosentan. Digoxin may decrease the cardiotoxic activities of Letrozole. The serum concentration of Letrozole can be increased when it is combined with Ceritinib. The serum concentration of Methadone can be increased when it is combined with Letrozole. The serum concentration of Letrozole can be decreased when it is combined with Siltuximab. The metabolism of Letrozole can be decreased when combined with Isradipine. The serum concentration of Letrozole can be increased when it is combined with Osimertinib. Cyclophosphamide may increase the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be decreased when combined with Cyclosporine. The metabolism of Letrozole can be decreased when combined with Rucaparib. The serum concentration of Letrozole can be decreased when it is combined with Dabrafenib. The metabolism of Letrozole can be decreased when combined with Telaprevir. The metabolism of Letrozole can be decreased when combined with Doxycycline. The metabolism of Letrozole can be increased when combined with Carbamazepine. The metabolism of Letrozole can be decreased when combined with Clarithromycin. The metabolism of Letrozole can be decreased when combined with Clemastine. The serum concentration of Letrozole can be increased when it is combined with Aprepitant. The metabolism of Letrozole can be decreased when combined with Dihydroergotamine. Trastuzumab may increase the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be decreased when combined with Nelfinavir. The serum concentration of Letrozole can be decreased when it is combined with Deferasirox. The metabolism of Letrozole can be decreased when combined with Isavuconazonium. The metabolism of Letrozole can be decreased when combined with Lovastatin. The metabolism of Letrozole can be decreased when combined with Dronedarone. The metabolism of Letrozole can be decreased when combined with Atazanavir. Bevacizumab may increase the cardiotoxic activities of Letrozole. The serum concentration of Letrozole can be decreased when it is combined with Tocilizumab. The serum concentration of Letrozole can be increased when it is combined with Dasatinib. The serum concentration of Letrozole can be increased when it is combined with Mifepristone. The metabolism of Letrozole can be decreased when combined with Olaparib. The metabolism of Letrozole can be decreased when combined with Atomoxetine. The serum concentration of Letrozole can be decreased when it is combined with Tamoxifen. Ouabain may decrease the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be increased when combined with Fosphenytoin. The metabolism of Letrozole can be increased when combined with Primidone. Oleandrin may decrease the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be increased when combined with Pentobarbital. The metabolism of Letrozole can be decreased when combined with Ziprasidone. The metabolism of Letrozole can be increased when combined with Phenytoin. The serum concentration of Letrozole can be decreased when it is combined with Enzalutamide. The serum concentration of Letrozole can be decreased when it is combined with Vemurafenib. The serum concentration of the active metabolites of Artesunate can be reduced when Artesunate is used in combination with Letrozole resulting in a loss in efficacy. The metabolism of Letrozole can be decreased when combined with Posaconazole. The metabolism of Letrozole can be decreased when combined with Cobicistat. The serum concentration of Letrozole can be increased when it is combined with Palbociclib. Digoxin Immune Fab (Ovine) may decrease the cardiotoxic activities of Letrozole. The metabolism of Letrozole can be decreased when combined with Ticlopidine. The risk or severity of adverse effects can be increased when Docetaxel is combined with Letrozole. The metabolism of Letrozole can be decreased when combined with Nicotine. The metabolism of Letrozole can be decreased when combined with Nilotinib. The risk or severity of adverse effects can be increased when Cabazitaxel is combined with Letrozole. The metabolism of Letrozole can be decreased when combined with Darunavir. Acetyldigitoxin may decrease the cardiotoxic activities of Letrozole. The serum concentration of Letrozole can be increased when it is combined with Simeprevir. The metabolism of Letrozole can be decreased when combined with Telithromycin. The serum concentration of Letrozole can be increased when it is combined with Luliconazole. The metabolism of Letrozole can be increased when combined with Lumacaftor. The metabolism of Letrozole can be decreased when combined with Delavirdine. The metabolism of Letrozole can be decreased when combined with Fluvoxamine. The metabolism of Letrozole can be decreased when combined with Imatinib. The serum concentration of Letrozole can be increased when it is combined with Stiripentol. The serum concentration of Letrozole can be increased when it is combined with Ivacaftor. The metabolism of Letrozole can be decreased when combined with Itraconazole. The metabolism of Letrozole can be decreased when combined with Fluconazole.