because of increased risk for serious infections.dichlorphenamidedichlorphenamide and leflunomide both decrease serum potassium. Use Caution/Monitor.echinacealeflunomide increases and echinacea decreases immunosuppressive effects; risk of infection. Effect of interaction is not clear, use caution. Use Caution/Monitor.eltrombopagleflunomide will increase the level or effect of eltrombopag by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.eluxadolineeluxadoline increases levels of leflunomide by decreasing metabolism. Use Caution/Monitor. Eluxadoline may increase the systemic exposure of coadministered BCRP substrates.encorafenibencorafenib will increase the level or effect of leflunomide by Other (see comment). Modify Therapy/Monitor Closely. Encorafenib (a BCRP inhibitor) may increase the concentration and toxicities of BCRP substrates. Closely monitor for signs and symptoms of increased exposure and consider adjusting the dose of these substrates.ethotoinleflunomide will increase the level or effect of ethotoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.etravirineleflunomide will increase the level or effect of etravirine by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.fingolimodleflunomide increases effects of fingolimod by immunosuppressive effects; risk of infection. Modify Therapy/Monitor Closely. Concomitant therapy is expected to increase the risk of immunosuppression. Use caution when switching patients from long-acting therapies with immune effects. .fosphenytoinleflunomide will increase the level or effect of fosphenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.fostamatinibfostamatinib will increase the level or effect of leflunomide by decreasing metabolism. Use Caution/Monitor. Concomitant use of fostamatinib may increase concentrations of BCRP substrate drugs. Monitor for toxicities of BCRP substrate drug that may require dosage reduction when given concurrently with fostamatinib.fostemsavirfostemsavir will increase the level or effect of leflunomide by Other (see comment). Modify Therapy/Monitor Closely. Fostemsavir inhibits BCRP transporters. If possible, avoid coadministration or modify dose of BCRP substrate coadministered with fostemsavir.glecaprevir/pibrentasvirglecaprevir/pibrentasvir will increase the level or effect of leflunomide by decreasing metabolism. Use Caution/Monitor. Glecaprevir/pibrentasvir may increase plasma concentration of BCRP substrates.haemophilus influenzae type b vaccineleflunomide decreases effects of haemophilus influenzae type b vaccine by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Avoid vaccination during chemotherapy or radiation therapy if possible because antibody response might be suboptimal. Patients vaccinated within a 14-day period before starting or during immunosuppressive therapy should be revaccinated =3 months after therapy is discontinued if immune competence has been restored. .hydroxyureahydroxyurea, leflunomide. Other (see comment). Use Caution/Monitor. Comment: Combination therapy may lead to increased risk of infection.ifosfamideifosfamide increases toxicity of leflunomide by Other (see comment). Use Caution/Monitor. Comment: Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.influenza virus vaccine quadrivalent, recombinantleflunomide decreases effects of influenza virus vaccine quadrivalent, recombinant by pharmacodynamic antagonism. Use Caution/Monitor. Immune response to vaccine may be decreased in immunocompromised individuals.influenza virus vaccine trivalent, recombinantleflunomide decreases effects of influenza virus vaccine trivalent, recombinant by pharmacodynamic antagonism. Use Caution/Monitor. Immune response to vaccine may be decreased in immunocompromised individuals.isavuconazonium sulfateleflunomide and isavuconazonium sulfate both decrease immunosuppressive effects; risk of infection. Use Caution/Monitor.lomustinelomustine increases toxicity of leflunomide by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.losartanleflunomide will increase the level or effect of losartan by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. May inhibit the conversion of losartan to its active metabolite E-3174. Importance of interaction not established; monitor individual therapeutic response to determine losartan dosage.leflunomide decreases effects of losartan by decreasing metabolism. Use Caution/Monitor. May inhibit the conversion of losartan to its active metabolite E-3174. Importance of interaction not established; monitor individual therapeutic response to determine losartan dosage.maitakeleflunomide increases and maitake decreases immunosuppressive effects; risk of infection. Effect of interaction is not clear, use caution. Use Caution/Monitor.mechlorethaminemechlorethamine increases toxicity of leflunomide by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.melphalanmelphalan, leflunomide. Either increases effects of the other by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.meningococcal group B vaccineleflunomide decreases effects of meningococcal group B vaccine by pharmacodynamic antagonism. Use Caution/Monitor. Individuals with altered immunocompetence may have reduced immune responses to the vaccine.mercaptopurineleflunomide and mercaptopurine both increase immunosuppressive effects; risk of infection. Use Caution/Monitor.methotrexateleflunomide increases levels of methotrexate by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Additive hepatotoxicity, pancytopenia. If leflunomide and methotrexate are given concomitantly, monitor liver toxicity with ALT, AST, and serum albumin testing. Also, monitor platelets, WBC count, hemoglobin, or hematocrit at baseline and monthly for 6 months following initiation and every 6-8 weeks thereafter.nateglinideleflunomide will increase the level or effect of nateglinide by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.ocrelizumabocrelizumab increases toxicity of leflunomide by unknown mechanism. Modify Therapy/Monitor Closely. Coadminstration of leflunomide and ocrelizumab may cause increased risk of infections, pancytopenia, agranulocytosis and thrombocytopenia.ofatumumab SCofatumumab SC, leflunomide. Either increases effects of the other by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider the risk of additive immune system effects when coadministering immunosuppressive therapies with coadministration. When switching from therapies with immune effects, take into account the duration and mechanism of action of these therapies when initiating ofatumumab SC.olaparibleflunomide and olaparib both increase pharmacodynamic synergism. Use Caution/Monitor. Coadministration with other other myelosuppressive anticancer agents, including DNA damaging agents, may potentiate and prolongate the myelosuppressive toxicity. oteseconazoleoteseconazole will increase the level or effect of leflunomide by Other (see comment). Modify Therapy/Monitor Closely. Otesezonale, a BCRP inhibitor, may increase the effects and risk of toxicities of BCRP substrates. Use lowest starting dose of BCRP substrate, or consider reducing BCRP substrate dose.oxaliplatinoxaliplatin increases toxicity of leflunomide by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.ozanimodozanimod, leflunomide. Either increases effects of the other by immunosuppressive effects; risk of infection. Use Caution/Monitor. Coadministration with immunosuppressive therapies may increase the risk of additive immune effects during therapy and in the weeks following administration. When switching from drugs with prolonged immune effects, consider the half-life and mode of action of these drugs in order to avoid unintended additive immunosuppressive effects.parecoxibleflunomide will increase the level or effect of parecoxib by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoinleflunomide will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.poliovirus vaccine inactivatedleflunomide decreases effects of poliovirus vaccine inactivated by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Avoid vaccination during chemotherapy or radiation therapy if possible because antibody response might be suboptimal. Patients vaccinated within a 14-day period before starting or during immunosuppressive therapy should be revaccinated =3 months after therapy is discontinued if immune competence has been restored. .ponatinibponatinib increases levels of leflunomide by Other (see comment). Use Caution/Monitor.ponesimodponesimod and leflunomide both increase immunosuppressive effects; risk of infection. Use Caution/Monitor. Caution if coadministered because of additive immunosuppressive effects during such therapy and in the weeks following administration. When switching from drugs with prolonged immune effects, consider the half-life and mode of action of these drugs to avoid unintended additive immunosuppressive effects.procarbazineprocarbazine increases toxicity of leflunomide by immunosuppressive effects; risk of infection. Use Caution/Monitor. Consider not using a leflunomide loading dose in patients receiving other immunosuppressants. Monitor for bone marrow suppression at least monthly in patients concomitantly using leflunomide and another immunosuppressant.regorafenibregorafenib will increase the level or effect of leflunomide by Other (see comment). Modify Therapy/Monitor Closely. Regorafenib likely inhibits BCRP (ABCG2) transport. Coadministration with a BCRP substrate may increase systemic exposure to the substrate and related toxicity.safinamidesafinamide will increase the level or effect of leflunomide by Other (see comment). Use Caution/Monitor. Safinamide and its major metabolite may inhibit intestinal BCRP. Monitor BCRP substrates for increased pharmacologic or adverse effects.siponimodsiponimod and leflunomide both increase immunosuppressive effects; risk of infection. Use Caution/Monitor. Caution if coadministered because of additive immunosuppressive effects during such therapy and in the weeks following administration. When switching from drugs with prolonged immune effects, consider the half-life and mode of action of these drugs to avoid unintended additive immunosuppressive effects.sipuleucel-Tleflunomide decreases effects of sipuleucel-T by pharmacodynamic antagonism. Modify Therapy/Monitor Closely.sofosbuvir/velpatasvirsofosbuvir/velpatasvir will increase the level or effect of leflunomide by Other (see comment). Use Caution/Monitor. Velpatasvir is an inhibitor of the drug transporter BCRP. Coadministration may increase systemic exposure of drugs that are BCRP substrates.stiripentolstiripentol will increase the level or effect of leflunomide by Other (see comment). Modify Therapy/Monitor Closely. Stiripentol is a BCRP transport inhibitor. Consider dosage reduction for BCRP substrates if adverse effects are experienced when coadministered.tafamidistafamidis will increase the level or effect of leflunomide by Other (see comment). Use Caution/Monitor. Tafamidis inhibits breast cancer resistant protein (BCRP) in vitro and may increase exposure of BCRP substrates following tafamidis or tafamidis meglumine administration. Dosage adjustment of these BCRP substrates may be necessary.tafamidis megluminetafamidis meglumine will increase the level or effect of leflunomide by Other (see comment). Use Caution/Monitor. Tafamidis inhibits breast cancer resistant protein (BCRP) in vitro and may increase exposure of BCRP substrates following tafamidis or tafamidis meglumine administration. Dosage adjustment of these BCRP substrates may be necessary.tamoxifenleflunomide, tamoxifen. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. CYP2C9/10 inhibition decreases tamoxifen metabolism to active metabolites.trastuzumabtrastuzumab, leflunomide. Either increases toxicity of the other by immunosuppressive effects; risk of infection. Use Caution/Monitor. Neutropenia or febrile neutropenia incidence were increased when trastuzumab was coadministered with myelosuppressive chemotherapy. .trastuzumab deruxtecantrastuzumab deruxtecan, leflunomide. Either increases toxicity of the other by immunosuppressive effects; risk of infection. Use Caution/Monitor. Neutropenia or febrile neutropenia incidence were increased when trastuzumab was coadministered with myelosuppressive chemotherapy. .ublituximabublituximab and leflunomide both increase immunosuppressive effects; risk of infection. Modify Therapy/Monitor Closely. Owing to potential additive immunosuppressive effects, consider duration of effect and mechanism of action of these therapies if coadministeredwarfarinleflunomide increases effects of warfarin by unspecified interaction mechanism. Use Caution/Monitor.zoster vaccine recombinantleflunomide decreases effects of zoster vaccine recombinant by pharmacodynamic antagonism. Use Caution/Monitor. Immunosuppressive therapies may reduce the effectiveness of zoster vaccine recombinant.Minor (17)activated charcoalactivated charcoal decreases levels of leflunomide by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.alosetronleflunomide will increase the level or effect of alosetron by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.bosentanleflunomide will increase the level or effect of bosentan by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.celecoxibleflunomide will increase the level or effect of celecoxib by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.diclofenacleflunomide will increase the level or effect of diclofenac by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.flurbiprofenleflunomide will increase the level or effect of flurbiprofen by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.fluvastatinleflunomide will increase the level or effect of fluvastatin by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.ibuprofenleflunomide will increase the level or effect of ibuprofen by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.ibuprofen IVleflunomide will increase the level or effect of ibuprofen IV by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.meloxicamleflunomide will increase the level or effect of meloxicam by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.piroxicamleflunomide will increase the level or effect of piroxicam by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.ramelteonleflunomide will increase the level or effect of ramelteon by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.rifampinrifampin increases effects of leflunomide by increasing metabolism. Minor/Significance Unknown. Leflunomide's effects due to its active metabolite.shark cartilageleflunomide, shark cartilage. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Enhanced anti angiogenesis (theoretical interaction).sulfamethoxazoleleflunomide will increase the level or effect of sulfamethoxazole by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.tolbutamideleflunomide will increase the level or effect of tolbutamide by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.voriconazoleleflunomide will increase the level or effect of voriconazole by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.acalabrutinibMonitor Closely (1)acalabrutinib increases levels of leflunomide by Other (see comment). Use Caution/Monitor. Comment: Acalabrutinib may increase exposure to coadministered BCRP substrates by inhibition of intestinal BCRP.activated charcoalMinor (1)activated charcoal decreases levels of leflunomide by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.adalimumabSerious - Use Alternative (1)adalimumab and leflunomide both increase immunosuppressive effects; risk of infection. Avoid or Use Alternate Drug.alefaceptSerious - Use Alternative (1)alefacept and leflunomide both increase immunosuppressive effects; risk of infection. Avoid or Use Alternate Drug.alosetronMinor (1)leflunomide will increase the level or effect of alosetron by affecting hepatic