Drug Interaction Report

QuiNIDine may significantly increase the blood levels of tetrabenazine. This may increase side effects such as sleepiness, abnormal involuntary muscle movements, Parkinson-like symptoms (slight shaking, body stiffness, trouble moving or keeping your balance), and an irregular heart rhythm problem called QT prolongation. The heart rhythm problem may be serious and potentially life-threatening, although it is a 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 any question or concerns. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with these medications, as well symptoms such as fever, heat intolerance, excessive sweating, stiff muscles, and difficulty moving or swallowing that do not have another obvious cause. Do not drive, operate heavy machinery, or do other dangerous activities until you know how these medications affect you. 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.

Do not consume grapefruit or grapefruit juice during treatment with quiNIDine unless specifically directed otherwise by your doctor. Grapefruit and grapefruit juice can interact with quiNIDine and increase the levels of quiNIDine in your body. If you are already consuming grapefruit products, do not increase or decrease the amount of these products in your diet without first talking to your doctor.

Alcohol can increase the nervous system side effects of tetrabenazine 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 tetrabenazine. Do not use more than the recommended dose of tetrabenazine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.