Drug Interaction Report

Before starting fingolimod, let your doctor know if you are currently receiving treatment with valbenazine. Using fingolimod in this situation can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. This is most likely to occur early on after you start treatment with fingolimod, especially within the first 20 hours after the first dose. You may also be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). On the other hand, it may be alright for you to use these medications together if you have been stable on fingolimod therapy for over a month while you start treatment with valbenazine. Talk to your doctor if you have any questions or concerns. Your first dose of fingolimod must be taken at your doctor's office or a hospital, and you will need to be observed for 6 hours or more afterwards. In the event that you restart the medication after an interruption in treatment, you may need to take the first dose again under medical observation depending on how long you were on the medication before you stopped, and how many days the interruption lasted. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with these medications, whether together or alone. 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.

Grapefruit and grapefruit juice may increase the blood levels and effects of valbenazine, such as drowsiness and an irregular heart rhythm problem called QT prolongation. Irregular heart rhythm problems may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have questions or concerns. Do not add grapefruit products to your diet, or increase or decrease the amount currently in your diet without first talking to your doctor. You may need a dose adjustment of valbenazine or more frequent monitoring by your doctor to safely use both valbenazine and grapefruit products. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with these medications. 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.