Drug Interaction Report

MONITOR CLOSELY: Coadministration of thalidomide with glucocorticoids and/or antineoplastic agents in the treatment of malignancy may potentiate the risk of thromboembolism. The exact mechanism is unknown but likely multifactorial. Thalidomide alone has been associated with the development of deep-vein thrombosis (DVT), and malignancy itself is also a common cause. In a study of 100 patients receiving induction chemotherapy (combinations of dexamethasone, vincristine, doxorubicin, cyclophosphamide, etoposide, and cisplatin) for multiple myeloma, the addition of thalidomide was associated with an increased incidence of DVT compared to chemotherapy without thalidomide (28% vs. 4%). Administration of thalidomide was safely resumed in 75% of patients after initiation of appropriate anticoagulation therapy. In another study, 9 of 21 (43%) patients with metastatic renal cell carcinoma (RCC) receiving gemcitabine, 5-FU, and thalidomide developed venous thromboembolism, including one case of fatal cardiac arrest. This rate is substantially higher than the 3% rate observed in a group of 125 patients previously treated at the same institution with similar regimens of gemcitabine and 5-FU but without thalidomide. It is also higher than the 9% rate (12 of 140 patients) the investigators found in a review of published data from five RCC trials that used thalidomide therapy without concomitant cytotoxic therapy. Another study found a significant association of DVT with exposure to doxorubicin in patients receiving thalidomide. Specifically, 31 of 192 (16%) multiple myeloma patients treated with DT-PACE (a regimen of dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide, and etoposide) developed DVT, while only 1 of 40 (2.5%) did so on DCEP-T (similar to DT-PACE but without doxorubicin). The time to DVT was also significantly decreased with doxorubicin exposure. In a pooled analysis of 39 prospectively monitored clinical trials involving 1784 thalidomide-treated patients, the incidence of thromboembolism was 5% when thalidomide was used as a single agent, 13% when combined with corticosteroids (8% to 26% has been reported in individual studies with dexamethasone), and 17% when combined with chemotherapy. Among thalidomide-treated patients with multiple myeloma, thromboembolism rates ranged from a low of 1/30 among those treated with concomitant cyclophosphamide, etoposide, and cisplatin to a high of about 1/3 in those treated with doxorubicin-containing regimens.

MANAGEMENT: Close monitoring for DVT or pulmonary embolism is recommended in patients who require thalidomide therapy in combination with glucocorticoids and/or cytotoxic agents. Patients should be advised to seek medical attention if they develop potential signs and symptoms of thromboembolism such as chest pain, shortness of breath, and pain or swelling in the arms or legs. Prophylaxis with anticoagulants such as low-molecular weight heparins or warfarin may be appropriate, but the decision to take thromboprophylactic measures should be made after careful assessment of underlying risk factors. If a thromboembolic event occurs during therapy with thalidomide, treatment must be discontinued and standard anticoagulation therapy started. Once anticoagulation is stabilized and complications of the thromboembolic event under control, thalidomide may be restarted at the original dose if benefit is deemed to outweigh the risks. Anticoagulation therapy should be continued during the remaining course of thalidomide treatment.

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.

MONITOR: Thalidomide can cause bradycardia and may have additive effects with other drugs that decrease heart rate. Cases of bradycardia have been associated with thalidomide use, some requiring medical interventions. The clinical significance and underlying etiology of the bradycardia observed with thalidomide treatment have not been established. However, the potential for additive bradycardic effects should be considered when used with other drugs that slow cardiac conduction such as beta-blockers, calcium channel blockers, digitalis, flecainide, moricizine, and propafenone. Non-cardiac drugs that may also cause bradycardia include atazanavir, lacosamide, lithium, mefloquine, succinylcholine, H2-receptor antagonists, tricyclic antidepressants, and anticholinesterase or cholinergic agents. Because bradycardia is a risk factor for torsade de pointes arrhythmia, concerns also exist when thalidomide is used with drugs that prolong the QT interval or cause torsade de pointes.

MANAGEMENT: Caution is advised when thalidomide is used with drugs that can slow the heart rate or induce torsade de pointes arrhythmia. Patients should be monitored for bradycardia, atrioventricular block and syncope, and advised to seek medical attention if they experience dizziness, lightheadedness, fainting, shortness of breath, or slow or irregular heartbeat. A dose reduction of thalidomide or discontinuation may be required.

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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.