Drug Interactions between pimavanserin and vasopressin

GENERALLY AVOID: Pimavanserin may cause dose-related 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. In a thorough QTc study conducted in 252 healthy subjects, the maximum mean change in QTc interval from baseline was 13.5 msec at twice the therapeutic dosage given to steady state. In 6-week premarketing placebo-controlled effectiveness studies, mean increases in QTc interval were approximately 5 to 8 msec in patients receiving the recommended pimavanserin dosage of 34 mg once daily. Sporadic QTcF values >=500 msec and change from baseline values >=60 msec were observed in subjects treated with pimavanserin, although the incidence was generally similar to that reported for placebo groups. There were no reports of torsade de pointes arrhythmia or differences from placebo in any other adverse reactions associated with delayed ventricular repolarization. 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). The extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Coadministration of pimavanserin with other drugs that can prolong the QT interval should generally be avoided. Caution and clinical monitoring are recommended if concomitant use is required. Patients should have regular ECGs and be monitored for arrhythmias when QT interval is prolonged. 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.