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 may delay and reduce the absorption of voclosporin, which may lead to lower blood levels of the medication and possibly reduced effectiveness. Voclosporin should be taken on an empty stomach at least 1 hour before or 2 hours after food. This will make it easier for your body to absorb the medication. Also, while taking voclosporin, you should avoid grapefruits and grapefruit juice. Grapefruit can raise the blood levels of voclosporin in your body and lead to increased adverse effects. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor. Also, if you are taking voclosporin you should avoid potassium-containing salt substitutes or over-the-counter potassium supplements without first talking to your doctor. Taking voclosporin together with these salt substitutes or supplements may cause high levels of potassium in your blood. High levels of potassium can cause weakness, irregular heartbeat, confusion, tingling of the extremities, or feelings of heaviness in the legs. Call your doctor at once if you have any of these symptoms. 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.