Drug Interactions between alfuzosin and Risperdal M-Tab

MONITOR: Neuroleptic agents may potentiate the hypotensive effect of alfuzosin secondary to their peripheral alpha1-adrenergic blocking activity. Orthostatic hypotension and syncope associated with vasodilation may occur, particularly during the initial dose-titration period of neuroleptic therapy. In addition, alfuzosin may cause modest prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval including many neuroleptics 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 the QT interval. During a clinical study involving 45 healthy male subjects, average prolongation of QTc interval at peak plasma concentrations was less with single doses of alfuzosin 10 mg than with alfuzosin 40 mg, and both were less than with moxifloxacin 400 mg. Heart rate increased by an average of 5.2 bpm with alfuzosin 10 mg, 5.8 bpm with alfuzosin 40 mg, and 2.8 bpm with moxifloxacin 400 mg.

MANAGEMENT: Close clinical monitoring for adverse effects is recommended during concurrent therapy. A lower starting dosage and slower titration of the neuroleptic agent may be appropriate in patients receiving alfuzosin, especially if they are elderly. Patients should be advised to notify their physician if they experience orthostatic symptoms (dizziness, lightheadedness, syncope), and to seek medical help if they experience palpitations and fast/ or irregular heartbeats.