Drug Interactions between crizotinib and moxifloxacin / triamcinolone

MONITOR CLOSELY: Concomitant administration of corticosteroids may potentiate the risk of tendinitis and tendon rupture associated with fluoroquinolone treatment. The mechanism is unknown. Tendinitis and tendon rupture have most frequently involved the Achilles tendon, although cases involving the rotator cuff (the shoulder), the hand, the biceps, and the thumb have also been reported. Some have required surgical repair or resulted in prolonged disability. Tendon rupture can occur during or up to several months after completion of fluoroquinolone therapy.

MANAGEMENT: Caution is recommended if fluoroquinolones are prescribed in combination with corticosteroids, particularly in patients with other concomitant risk factors (e.g., age over 60 years; recipient of kidney, heart, and/or lung transplant). Patients should be advised to stop taking the fluoroquinolone, avoid exercise and use of the affected area, and promptly contact their physician if they experience pain, swelling, or inflammation of a tendon. In general, fluoroquinolones should only be used to treat conditions that are proven or strongly suspected to be caused by bacteria and only if the benefits outweigh the risks.

GENERALLY AVOID: Crizotinib can cause prolongation of the QT interval, which pharmacokinetic/pharmacodynamic modeling indicate may be concentration-dependent. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. In clinical trials done in adults on crizotinib (250 mg twice daily) QTcF (Fridericia corrected QT interval) prolongation greater than or equal to 500 msec was observed in 34 of 1619 (2.1%) and an increase from baseline QTcF greater than or equal to 60 msec was observed in 79 of 1585 patients (5%). In clinical studies of pediatric patients (dosed according to body surface area), a prolonged QT interval was observed in approximately 4% of patients. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia, hypocalcemia). Moreover, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Concomitant use of crizotinib with drugs that prolong the QT interval should generally be avoided. ECG and serum electrolytes, including potassium, magnesium, and calcium, should be monitored before starting crizotinib therapy and periodically during treatment according to the manufacturer's labeling. Electrolytes should be replaced as clinically indicated. Crizotinib should not be started if baseline QTc (QT corrected for heart rate) is greater than 500 msec. Likewise, treatment should be interrupted in patients who develop a QTc greater than 500 msec on at least 2 separate ECGs. Once the QTc has recovered to baseline or less than 481 msec, crizotinib can be resumed at the next lower dosage recommended in the manufacturer's labeling. Crizotinib should be permanently discontinued if the patient has a QTc greater than 500 msec or a change greater than or equal to 60 msec from baseline with torsade de pointes, polymorphic ventricular tachycardia, or signs/symptoms of a serious arrhythmia. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.