Coadministration has not been studied. Methotrexate is predominantly eliminated unchanged via the kidneys, with minimal metabolism. Methotrexate is a substrate of BCRP and concentrations may increase due to inhibition of BCRP by ritonavir, however, the clinical relevance of this is unknown. Note, some methotrexate product labels contraindicate its use or advise caution in immunodeficiency and some contraindicate its use in HIV infection.