Dextromethorphan-Quinidine

Dextromethorphan-Quinidine is a combination medication used to treat the symptoms of Pseudobulbar Affect. 

• Dextromethorphan-Quinidine is available under the following different brand names: Nuedexta

Common side effects of Dextromethorphan-Quinidine include:

• Dizziness,
• Weakness,
• Diarrhea,
• Gas,
• Vomiting,
• Flu symptoms,
• Cough, and
• Abnormal liver function tests

Serious side effects of Dextromethorphan-Quinidine include:

• Hives,
• Difficulty breathing,
• Swelling of the face, lips, tongue, or throat,
• Fast or pounding heartbeats,
• Fluttering in the chest,
• Shortness of breath,
• Sudden dizziness,
• Easy bruising or bleeding,
• Nosebleeds,
• Bleeding gums,
• Pain or burning while urination,
• Fever,
• Right-sided upper stomach pain,
• Vomiting,
• Loss of appetite,
• Yellowing of the skin or eyes,
• Not feeling well,
• Muscle or joint pain,
• Flu symptoms,
• Chest pain,
• Rash or patchy skin color that worsens in sunlight,
• Agitation,
• Hallucinations,
• Fever,
• Sweating,
• Shivering,
• Fast heart rate,
• Muscle stiffness,
• Twitching,
• Loss of coordination,
• Nausea,
• Vomiting, and
• Diarrhea

Rare side effects of Dextromethorphan-Quinidine include:

• none 

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult dosage

Dextromethorphan-Quinidine

• Capsule
  • 20 mg/10 mg

Pseudobulbar Affect

Adult dosage

• 1 capsule orally once a day for 7 days, THEN 1 capsule every 12 hours

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Dextromethorphan-Quinidine has severe interactions with at least 73 other drugs.
• Dextromethorphan-Quinidine has serious interactions with at least 224 other drugs.
• Dextromethorphan-Quinidine has moderate interactions with at least 253 other drugs.
• Dextromethorphan-Quinidine has minor interactions with at least 21 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, or if you have health questions or concerns.

Contraindications

• Hypersensitivity
• History of quinine, mefloquine, or quinidine-induced thrombocytopenia, hepatitis, bone marrow depression, or a lupus-like syndrome
• Concomitant use with drugs containing quinidine, quinine, or mefloquine
• Coadministration of MAOIs or use within 14 days
• Drugs that both prolong QT interval and are metabolized by CYP2D6 (.g, thioridazine, pimozide)
• Complete AV block (without implanted pacemakers)
• Prolonged QT interval, congenital long QT syndrome, or history of torsades de pointes or heart failure

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Dextromethorphan-Quinidine?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Dextromethorphan-Quinidine?”

Cautions

• Quinidine can cause immune-mediated thrombocytopenia (discontinue if thrombocytopenia occurs)
• Hepatotoxicity reported within the first few weeks following the initiation of quinidine
• Monitor for QTc prolongation if concomitant use of that prolongs QT interval cannot be avoided or concomitant CYP3A4 used
• Quinidine may cause anticholinergic effects and exacerbate certain conditions (.g, myasthenia gravis)
• Monitor ECG in patients with left ventricular hypertrophy or left ventricular dysfunction
• Dextromethorphan may cause serotonergic effects; monitor for worsening in myasthenia gravis and other sensitive conditions
• Use caution with CYP2D6 poor metabolizers
• CYP3A4 inhibitors may increase quinidine serum levels and risk for QT prolongation
• Coadministration with CYP2D6 substrates other than dextromethorphan that cause accumulation of parent drug and/or failure of metabolite formation may decrease safety and/or efficacy of concomitant CYPD6 metabolite zed drugs; adjust the dose of CYPD6 substrate or use alternative therapy when indicated
• Concomitant use of dextromethorphan with serotonergic drugs (.g, SSRIs, the  TCAs) may increase the risk for serotonin syndrome
• Quinidine may increase digoxin levels (as much as double) by inhibiting P-glycoprotein
• Coadministration with alcohol or other CNS depressants may cause additive effects
• May cause dizziness; use precautions to reduce falls

Pregnancy and Lactation

• There are no adequate data on the developmental risk associated with use in pregnant women
• Lactation
  • Quinidine is excreted in human milk; unknown whether dextromethorphan is excreted in human milk
  • There are no data on the effects of quinidine or dextromethorphan on the breastfed infant or the effects on milk production
  • There are no data on the effects of quinidine or dextromethorphan on the breastfed infant or milk production
  • Developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for therapy and any potential adverse effects on the breastfed infant from therapy or underlying maternal condition