Drug Interactions between Remeron SolTab and Ultane

MONITOR: Available data suggest that mirtazapine may cause mild prolongation of the QT interval. 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. Using exposure response analysis, a positive relationship between mirtazapine concentrations and prolongation of the QTc interval was identified in a clinical randomized trial with placebo and positive (moxifloxacin) controls involving 54 healthy volunteers. However, the degree of QT prolongation observed with both the 45 mg (therapeutic) and 75 mg (supratherapeutic) doses of mirtazapine was not at a level generally considered to be clinically meaningful. In 6-week placebo-controlled trials where a total of 338 patients received mirtazapine and 261 patients received placebo, QTc prolongation >=500 msec was not observed among mirtazapine-treated patients. Mean change in QTc was +1.6 msec for mirtazapine and -3.1 msec for placebo, which are well below the generally accepted critical threshold for cardiovascular safety. Nonetheless, cases of QT prolongation, torsade de pointes, ventricular tachycardia, and sudden death, have been reported during postmarketing use of mirtazapine according to the manufacturer. The majority of reports occurred in association with overdose or in patients with other risk factors for QT prolongation, including concomitant use of QT-prolonging medications. 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). In addition, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Caution is recommended if mirtazapine is used in combination with other drugs that can prolong the QT interval. 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.

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