Drug Interaction Report

GENERALLY AVOID: Coadministration of tofacitinib with other immuno- or myelosuppressive agents may potentiate the risk of infections as well as lymphoma and other malignancies. Serious and sometimes fatal infections due to bacterial, mycobacterial, invasive fungal, viral, or other opportunistic pathogens have been reported in patients receiving tofacitinib, most of whom were taking concomitant immunosuppressants such as methotrexate or corticosteroids. Lymphoma and other malignancies have also been observed with tofacitinib use, with or without concomitant immunosuppressants. Epstein Barr virus-associated posttransplant lymphoproliferative disorder has been observed at an increased rate in renal transplant patients treated with tofacitinib and concomitant immunosuppressive agents (basiliximab, high-dose corticosteroids, and mycophenolic acid) relative to cyclosporine plus the same induction regimen (2.3% vs. 0%).

MANAGEMENT: Concomitant use of tofacitinib with immuno- or myelosuppressive agents should generally be avoided. If coadministration is necessary, close monitoring is advised for the development of infections, including the possible development of tuberculosis in patients who tested negative for latent tuberculosis infection prior to initiating therapy. Lymphocyte and neutrophil counts as well as hemoglobin should be evaluated at baseline and regularly during therapy, and tofacitinib dosage adjusted as necessary in accordance with the product labeling. Patients should be advised to contact their physician if they develop signs and symptoms of infection such as fever, chills, diarrhea, sore throat, muscle aches, shortness of breath, blood in phlegm, weight loss, red or inflamed skin, body sores, and pain or burning during urination. If a serious infection, an opportunistic infection, or sepsis develops, tofacitinib should be interrupted until the infection is controlled.

MONITOR CLOSELY: Coadministration with folate therapy may potentiate the pharmacologic effects of 5-fluorouracil (5-FU). The exact mechanism of interaction is unknown. Although enhancement of 5-FU cytotoxicity may be used to advantage in some cancer patients, increased toxicity should also be considered. Deaths from severe enterocolitis, diarrhea, and dehydration have been reported in elderly patients receiving weekly leucovorin and fluorouracil. In a clinical study consisting of 148 patients with advanced untreated colorectal cancer, weekly administration of 5-FU (600 mg/m2) in combination with leucovorin (500 mg/m2) was associated with a higher response rate than 5-FU alone (23% versus 8%). However, the combination was also more toxic than 5-FU alone, as evidenced by a higher incidence of grade 3 to 4 diarrhea (19.5% versus 8.5%) and conjunctivitis (26.5% versus 5.6%), as well as one recorded toxic death versus none. No differences in median survival and time to progression were observed between the two groups. Similar results were observed in another study with capecitabine, a prodrug of 5-FU. The interaction has also been reported with folic acid. A published case report describes two patients who were hospitalized for presumed 5-FU toxicity (anorexia, severe mouth ulceration, bloody diarrhea, vaginal bleeding) during concomitant treatment with a multivitamin containing folic acid (0.5 mg in one and 5 mg in the other). Both patients tolerated subsequent courses of 5-FU at the previous dosage following discontinuation of the multivitamin. Another published report describes a breast cancer patient who died during treatment with capecitabine (2500 mg/m2 daily for 14 days every 3 weeks) while taking folic acid 15 mg/day. The patient developed diarrhea, vomiting, and hand-foot syndrome eight days after starting capecitabine therapy. Her condition improved briefly following discontinuation of capecitabine and then folic acid, but she subsequently developed necrotic colitis and died from septic shock and vascular collapse.

MANAGEMENT: Caution is advised if 5-FU or any of its prodrugs (e.g., capecitabine, tegafur) are prescribed in combination with leucovorin. A lower dosage of 5-FU or the prodrug may be required. Therapy with leucovorin and fluorouracil should not be initiated or continued in patients with symptoms of gastrointestinal toxicity until such symptoms have resolved. Closely monitor patients with diarrhea until it resolves. Monitor for other potential toxicities of 5-FU such as neutropenia, thrombocytopenia, stomatitis, cutaneous reactions, and neuropathy. Patients should be instructed to avoid taking folic acid supplementation or multivitamin preparations containing folic acid without first speaking with their physician.

MONITOR: Grapefruit juice may increase the plasma concentrations of tofacitinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The extent and clinical significance are unknown. Moreover, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability.

MANAGEMENT: Until more information is available, some authorities recommend avoiding consumption of grapefruit juice during tofacitinib therapy (Canada). Patients receiving tofacitinib therapy who ingest grapefruits or grapefruit juice should be monitored for adverse effects and undue fluctuations in plasma drug levels.