Drug Interactions between infliximab and letrozole / ribociclib

MONITOR CLOSELY: The use of tumor necrosis factor (TNF) blockers with other immunosuppressive or myelosuppressive agents may increase the risk of infections. Serious infections and sepsis, including fatalities, have been reported with the use of TNF blockers, particularly in patients on concomitant immunosuppressive therapy. Agents that may be significantly myelo- or immunosuppressive include antineoplastic agents, radiation, zidovudine, linezolid, some antirheumatic agents, high dosages of corticosteroids or adrenocorticotropic agents (greater than 10 mg/day to 1 mg/kg/day, whichever is less, of prednisone or equivalent for more than 2 weeks), and long-term topical or inhaled corticosteroids. Concomitant use of TNF blockers with other immunosuppressants such as azathioprine or mercaptopurine may also increase the risk of a rare and often fatal cancer of white blood cells known as hepatosplenic T-Cell lymphoma (HSTCL), which has primarily been reported in adolescent and young adult males receiving treatment for Crohn's disease or ulcerative colitis. Cases of HSTCL have also occurred during use of these agents alone. Because individuals with rheumatoid arthritis, Crohn's disease, ankylosing spondylitis, psoriatic arthritis, or plaque psoriasis may be more likely to develop lymphoma than the general population, it is difficult to assess the added risk of TNF blockers, azathioprine, and/or mercaptopurine.

MANAGEMENT: Patients receiving a TNF blocker alone or with other immunosuppressive or myelosuppressive agents should be monitored closely for the development of infections. TNF blocker therapy should be discontinued if a serious infection or sepsis occurs. Close monitoring for signs and symptoms of HSTCL (e.g., splenomegaly, hepatomegaly, abdominal pain, persistent fever, night sweats, weight loss) is also recommended during use of TNF blockers, particularly in combination with other immunosuppressants such as azathioprine and mercaptopurine.

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MONITOR: Coadministration with ribociclib may increase the plasma concentrations and pharmacologic effects of drugs that are substrates of CYP450 3A4. The proposed mechanism is decreased clearance due to ribociclib-mediated inhibition of CYP450 3A4 metabolism. In healthy study subjects, administration of midazolam, a sensitive CYP450 3A4 substrate, with multiple 400 mg daily doses of ribociclib increased the midazolam peak plasma concentration (Cmax) and systemic exposure (AUC) by 2.1-fold and 3.8-fold, respectively, compared to midazolam administered alone. When given at a clinically relevant dose of 600 mg daily, ribociclib is predicted to increase midazolam Cmax and AUC by 2.4-fold and 5.2-fold, respectively.

MANAGEMENT: Caution is advised when ribociclib is used concomitantly with drugs that undergo metabolism by CYP450 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever ribociclib is added to or withdrawn from therapy.

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