Drug Interactions between foscarbidopa / foslevodopa and valbenazine

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.

Alcohol can increase the nervous system side effects of foslevodopa such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with foslevodopa. You may experience reduced effectiveness of foslevodopa in the presence of foods or enteral (tube) feedings with a high protein content. This may make the symptoms of Parkinson's disease worse. Talk with your doctor or nutrition counselor about the best foods to eat while you are taking this medication. Contact your doctor if your condition changes.