CYP3A4 inducers, such as carbamazepine and modafinil, which are sometimes used as symptomatic treatment in MS, can slightly increase the elimination of fingolimod, therefore decreasing drug exposure; while potent CYP3A4 inhibitors, such as ketoconazole, block its hepatic metabolization, increasing the exposure to fingolimod and potentially the risk of side effects [17,18]. Here, CYP3A4 is linked to myeloid sarcoma.