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Precautions and Warnings With Dextromethorphan and Quinidine

Specific Dextromethorphan and Quinidine Precautions and Warnings

Some warnings and precautions to be aware of prior to taking this medicine include the following:
  • Some people may experience an allergic, or hypersensitivity, reaction to dextromethorphan and quinidine. People who experience this reaction may develop a condition known as thrombocytopenia, or a decrease in the amount of platelets in the blood. Contact your healthcare provider immediately if you experience any signs of thrombocytopenia, including:
    • Lightheadedness
    • Chills
    • Fever
    • Nausea
    • Vomiting.
  • Dextromethorphan and quinidine may also cause a reaction known as lupus-like syndrome in some people. Contact your healthcare provider immediately if you develop any symptoms of lupus-like syndrome, including:
    • Joint and muscle pain
    • A rash
    • Swollen lymph nodes
    • Hives
    • Breathing problems.
  • Liver problems, including hepatitis, have been reported in people taking quinidine, one of the active ingredients in dextromethorphan and quinidine. Contact your healthcare provider immediately if you experience any signs of liver problems, including:
    • Dark urine
    • Loss of appetite
    • Fatigue or excessive tiredness
    • Pain in the right upper part of the (abdomen) stomach
    • Yellowing of the whites of the eyes or skin (jaundice).
  • Dextromethorphan and quinidine can cause a serious heart rhythm problem known as QT prolongation. People may have an increased risk for developing this problem if they have certain heart problems or are taking other medicines that may cause QT prolongation. 
If you are at risk for QT prolongation, your healthcare provider will likely recommend an electrocardiogram (ECG) before you begin dextromethorphan and quinidine, and right after your first dose. Contact your healthcare provider immediately if you feel faint, lose consciousness, or have heart palpitations (a pounding or racing heart) while taking this drug.
  • Dextromethorphan and quinidine could make you feel dizzy, which might cause you to fall down. Talk to your healthcare provider about ways to reduce your risk for falling, especially if you have fallen in the past or have a condition that affects your ability to move or walk.
  • Dextromethorphan and quinidine may cause a potentially dangerous group of symptoms called serotonin syndrome, especially when someone overdoses on this drug or takes it with other medications that affect serotonin levels (see Drug Interactions With Dextromethorphan and Quinidine). Contact your healthcare provider immediately if you notice any possible symptoms of serotonin syndrome, including:


    • Confusion
    • Seeing or hearing things that are not really there (hallucinations)
    • A fast heartbeat (tachycardia)
    • High blood pressure (hypertension)
    • Fever
    • Sweating
    • Shivering
    • Tremors
    • Muscle spasms
    • Overactive reflexes.
  • Dextromethorphan and quinidine will not work for everyone. Tell your healthcare provider if your symptoms do not improve, or get worse, while taking this drug.
  • Dextromethorphan and quinidine is a pregnancy Category C medication. This means that it may not be safe for use during pregnancy, although the full risks are unknown (see Nuedexta and Pregnancy).
  • It is unknown if dextromethorphan and quinidine passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Nuedexta and Breastfeeding).
Know the Signs - Concussion Safety

Dextromethorphan and Quinidine Information

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