Drug Interaction Report

Consumer information for this interaction is not currently available.

MONITOR: Tolterodine 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 QTc study conducted in 48 healthy subjects, the mean change in QTc interval from baseline to peak tolterodine concentration was 5 msec for immediate release tolterodine 2 mg twice daily. At twice the therapeutic dosage of tolterodine, 4 mg twice daily, the mean change in QTc interval from baseline to peak tolterodine concentration was 11.8 msec. The QTc interval increases in poor metabolizers of CYP450 2D6 administered tolterodine 2 mg twice daily were comparable to those observed in extensive metabolizers of CYP450 2D6 administered 4 mg twice daily in a pharmacokinetic/pharmacodynamic model. 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 tolterodine is used in combination with other drugs that can prolong the QT interval. Clinical and laboratory monitoring, including QTc interval and serum electrolytes, is advised. Patients should have regular ECGs and be monitored for arrhythmias when the QTc interval is prolonged. If the QTc interval becomes markedly prolonged or symptoms of arrhythmia occur, drug discontinuation should be considered. 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. Patients should be advised to notify their physician if they experience new or worsening side effects of tolterodine including severe blurry vision, difficulty urinating, dry mouth, headache, drowsiness, dizziness, or GI upset.

Food helps with the absorption of gepirone into the blood stream. You should take this medication with food at about the same time every day. You should not consume grapefruit or grapefruit products while taking this medication as they can increase the blood levels of gepirone in your body, putting you at a higher risk of serious side effects like serotonin syndrome or a change in the electrical activity of your heart called QT prolongation. Seek immediate medical attention if you experience any of the following signs or symptoms of these potentially life-threatening side effects: irregular or fast heartbeat, dizziness, lightheadedness, fainting, agitation, confusion, sweating, flushing, changes in blood pressure, seizures, hallucinations, or a loss of coordination. Talk to your doctor or pharmacist if you have questions on how to take this or other medications you are prescribed. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.