Drug Interactions between safinamide 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.

Safinamide may be taken with or without food. While there is no need to strictly avoid most foods and beverages that contain tyramine (usually aged, fermented, cured, smoked, or pickled foods such as air-dried and fermented meats or fish, aged cheeses, most soybean products, yeast extracts, red wine, beer, and sauerkraut) during treatment with safinamide, certain foods such as some of the aged cheeses (for example, Boursault, Liederkrantz, Mycella, and Stilton) and pickled herring may contain very high amounts of tyramine and should generally be avoided if possible. Consumption of very high levels of tyramine (greater than 150 mg) while on safinamide treatment may lead to dangerous increases in your blood pressure, a condition known as hypertensive crisis. Talk to your doctor or pharmacist if you are uncertain about what foods, if any, to avoid. You should seek immediate medical attention if you experience sudden and severe headache, blurred vision, confusion, seizures, chest pain, nausea or vomiting, sudden numbness or weakness (especially on one side of the body), speech difficulties, fever, sweating, lightheadedness, and/or fainting during treatment with safinamide, as these may be signs and symptoms of a hypertensive crisis. Do not take larger doses or use the medication more frequently than 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.