Interactions between idarubicin and Diskets (methadone)
methadone and idarubicin (Major Drug-Drug)
MONITOR CLOSELY: Methadone may cause dose-related prolongation of the QT interval. Coadministration with other agents that can prolong the QT interval may result in elevated risk of ventricular arrhythmias, including ventricular tachycardia and torsade de pointes, because of additive arrhythmogenic potential related to their effects on cardiac conduction. High dosages of methadone alone have been associated with QT interval prolongation and torsade de pointes. In a retrospective study of 17 methadone-treated patients who developed torsade de pointes, the mean daily dose was approximately 400 mg (range 65 to 1000 mg) and the mean corrected QT (QTc) interval on presentation was 615 msec. The daily methadone dose correlated positively with the QTc interval. Fourteen patients had at least one predisposing risk factor for arrhythmia (hypokalemia, hypomagnesemia, concomitant use of a medication known to prolong the QT interval or inhibit the metabolism of methadone, and structural heart disease), but these were not predictive of QTc interval. It is not known if any of the patients had congenital long QT syndrome.
MANAGEMENT: Caution is recommended when methadone is administered concomitantly with drugs that prolong the QT interval, particularly in the setting of chronic pain management or methadone maintenance for opioid dependency where high dosages may be employed, or if administered to patients with underlying risk factors. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, or syncope. If taking drugs that also cause central nervous system and/or hypotensive effects (e.g., psychotropic drugs like tricyclic antidepressants, phenothiazines, and neuroleptics), patients should be made aware of the possibility of additive effects with methadone and counseled to avoid activities requiring mental alertness until they know how these agents affect them.
