Drug Interaction Report

GENERALLY AVOID: Coadministration of deferiprone and other drugs that can cause neutropenia or agranulocytosis may increase the risk and/or severity of hematologic toxicity. Serious infection and death have been reported. The mechanism by which deferiprone leads to neutropenia or agranulocytosis is unknown. In pooled clinical trials of 642 patients with thalassemia syndromes, neutropenia occurred in 6.2% and agranulocytosis in 1.7% of deferiprone-treated patients. Similarly, agranulocytosis occurred in 1.5% of deferiprone-treated patients in pooled clinical trials of 196 patients with sickle cell disease or other anemias. Pediatric patients experienced a higher rate of decreases in neutrophil count when compared to adults being treated with deferiprone for the same condition. Neutropenia and agranulocytosis generally resolve upon discontinuation of deferiprone.

MANAGEMENT: Concomitant use of deferiprone with other drugs known to be associated with neutropenia or agranulocytosis should generally be avoided. Some authorities consider this combination to be contraindicated. If coadministration is unavoidable, the patient's baseline absolute neutrophil count (ANC) should be measured and then closely monitored during deferiprone therapy according to the manufacturer's product labeling. If neutropenia or infection develops, deferiprone and any other concomitant therapy associated with neutropenia or agranulocytosis should be discontinued. A complete blood cell (CBC) count, including a white blood cell (WBC) count corrected for the presence of nucleated red blood cells, an ANC, and a platelet count should be obtained daily until recovery. Patients should be advised to seek immediate medical assistance if they develop symptoms of infection (e.g., fever, sore throat, flu-like symptoms). For patients who develop agranulocytosis (ANC less than 0.5 x 10^9/L), hospitalization should be considered, and deferiprone should not be resumed following recovery unless potential benefits outweigh the risks. Likewise, patients who develop neutropenia with deferiprone should not be rechallenged unless potential benefits outweigh the risks.

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.

GENERALLY AVOID: Pomegranates and grapefruit may increase the systemic exposure to ribociclib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in these fruits. Increased exposure to ribociclib may increase the risk of adverse effects such as infections, neutropenia, leukopenia, anemia, thrombocytopenia, anorexia, nausea, vomiting, diarrhea, stomatitis, alopecia, fatigue, headache, and abnormal liver function may be increased.

MANAGEMENT: Patients receiving ribociclib should avoid consumption of pomegranates or pomegranate juice and grapefruit or grapefruit juice during treatment.