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Dextromethorphan and Quinidine

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Why is this medication prescribed?

People with certain conditions, such as amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease; condition in which the nerves that control muscle movement slowly die, causing the muscles to shrink and weaken) or multiple sclerosis, may experience sudden, frequent, uncontrollable outbursts of crying or laughing known as pseudobulbar affect (PBA) (a disease in which the nerves do not function properly and patients may experience weakness, numbness, loss of muscle coordination and problems with vision, speech, and bladder control). The drug dextromethorphan belongs to the group of drugs known as central nervous system agents. It is unknown how PBA is treated by this medication in the brain. Quinidine belongs to the group of drugs known as antiarrhythmics. When used alongside dextromethorphan, quinidine increases the body’s supply of the latter substance.

How should this medicine be used?

Dextromethorphan and quinidine are sold as a capsule to be swallowed. It is typically given once day for seven days, with or without food. It is taken every 12 hours starting after 7 days. No more than two doses should be taken in a day. Make sure to wait 12 hours in between doses. Use quinidine and dextromethorphan daily at around the same time(s). Ask your doctor or pharmacist to explain any instructions on your prescription label that you are unsure about following. Dextromethorphan and quinidine should be taken exactly as prescribed. Never take it in larger or less amounts or more frequently than directed by your doctor.

Your doctor may periodically reassess whether you still require this medicine to manage your symptoms. Pay close attention to these guidelines.

Other uses for this medicine

Ask your doctor or pharmacist for more details if you believe this drug should be used for something else.

What special precautions should I follow?

Before taking dextromethorphan and quinidine,

  • If you have any allergies to dextromethorphan, quinidine (Quinidex), quinine (Qualaquin), mefloquine (Lariam), any other medications, or any of the substances in combination dextromethorphan and quinidine capsules, let your doctor and pharmacist know right once. Get an ingredient list from your pharmacist.
  • Inform your doctor if you are taking any medications that contain quinidine, such as mefloquine (Lariam), pimozide (Orap), quinine (Qualaquin), thioridazine, or other products (Quinidex). Dextromethorphan and quinidine should not be taken if you are taking one or more of these medications, according to your doctor.
  • Inform your doctor and pharmacist about any additional prescription and over-the-counter drugs, vitamins, dietary supplements, and herbal products you are now taking or intend to use. Incorporate any of the following: antidepressants such as fluoxetine (Prozac, Sarafem), clomipramine (Anafranil), desipramine (Doxepin, Sinequan), nefazodone, and paroxetine (Paxil, Pexeva); aprepitant (Emend); clarithromycin (Biaxin, Prevpac); and dextromethorphan-containing cough and cold remedies; cisapride, digoxin (Lanoxin, Digitek), erythromycin (E.E.S. E-Mycin, Erythrocin), fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), and some anti-HIV drugs like atazanavir (Reyataz), amprenavir (Agenerase), fosamprenavir (Lexiva), drugs for irregular heartbeats, including amiodarone (Cordarone), diltiazem (Cardizem, Cartia, Tiazac, others), disopyramide (Norpace), dofetilide (Tikosyn), procainamide (Procanbid, Pronestyl), sotalol (Betapace), and verapamil (Calan, Covera, Isoptin, Verelan, in Tarka); codeine, hydrocodone (in Hydrogesic, Lorcet, Lortab, Vicodin, Zydone, and other painkillers), methadone, moxifloxacin (Avelox), sparfloxacin (Zagam), and teliththromycin are examples of painkillers (Ketek). Also let your doctor or pharmacist know if you’ve recently stopped taking any of the following medicines: MAO inhibitors like phenelzine (Nardil), isocarboxazid (Marplan), linezolid (Zyvox), rasagiline (Azilect), selegiline (Eldepryl), and tranylcypromine (Parnate). Your physician might need to adjust the dosage of your drugs or keep a close eye on you for side effects. Dextromethorphan and quinidine may also interact with many other medications, so be sure to let your doctor know about all the drugs you are taking, even if they are not on this list.
  • When using quinidine, quinine, or mefloquine, disclose to your doctor if you have or have had had any of the following conditions: a decrease in the amount of blood cells in your bone marrow, lupus (a disease in which the body attacks its own tissues, causing damage and swelling), or hepatitis (swelling of the liver). Additionally let your doctor know if you currently or previously experienced heart failure or irregular heart rhythms. Quinidine and dextromethorphan should be avoided, according to your doctor.
  • Inform your physician if you have or have ever had myasthenia gravis (a nerve system ailment that results in muscle weakness), high blood pressure, a stroke, low potassium or magnesium levels in your blood, or heart, kidney, or liver disease.
  • Inform your doctor if you are expecting, intend to get pregnant, or are nursing a baby. If you become pregnant while using the combination of dextromethorphan and quinidine, call your doctor.
  • Inform the surgeon or dentist that you are taking dextromethorphan and quinidine if you are having surgery, including dental surgery.
  • You should be aware that quinidine and dextromethorphan both cause dizziness. While using this drug, it’s crucial to take extra precaution to prevent falls.
  • While taking dextromethorphan with quinidine, find out from your doctor whether drinking alcohol is safe for you. The adverse effects of this drug may be exacerbated by alcohol.

What special dietary instructions should I follow?

If you plan to consume grapefruits or grapefruit juice while taking this medication, consult your doctor.

Keep eating normally unless your doctor instructs you otherwise.

What should I do if I forget a dose?

Take the subsequent dose at the scheduled time instead of the missing one. To make up for a missing dose, do not take a second one. Ensure that there is a 12-hour gap between dosages.

What side effects can this medication cause?

Quinidine with dextromethorphan may have undesirable side effects. If any of these symptoms are severe or do not go away, consult your doctor:

  • Diarrhea
  • Vomiting
  • Gas
  • Stomach pain
  • Cough
  • Dry mouth or eyes
  • Weakness
  • Muscles cramping
  • Edoema of the lower legs, ankles, feet, or hands
  • Frequent, uncomfortable, or challenging urinating
  • Urine that is cloudy or has a strong odour

Some adverse effects may be severe. Call your doctor right away if you notice any of these signs:

  • Fever
  • Uncommon bruising or bleeding
  • Joint or muscle ache
  • Rash
  • Swelling of the lips, tongue, throat, or face
  • An enlarged lymph node
  • Hoarseness
  • Having trouble breathing
  • Lightheadedness
  • Fainting
  • Rapid heart rate

Quinidine and dextromethorphan may interact to produce additional negative effects. If you experience any strange issues while taking this medicine, contact your doctor right away.

You or your doctor can submit a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting programme online or by phone if you have a serious side event (1-800-332-1088).

What should I know about storage and disposal of this medication?

Keep this prescription tightly wrapped in the container it came in, out from the reach of children and animals. Keep it away from excessive heat and moisture at room temperature (not in the bathroom).

Unused prescriptions must be disposed of carefully to prevent pets, kids, and other people from ingesting them. You should not, however, dispose of this medication in the toilet. Instead, utilising a medicine take-back programme is the easiest approach to get rid of your medication. To find out about take-back programmes in your area, speak with your pharmacist or the garbage/recycling department in your city. If you do not have access to a take-back programme, see the FDA’s Safe Disposal of Medications website at for additional information.

Although many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and are simple for young children to open, it is crucial to keep all medications out of sight and out of reach of children. Always lock safety caps and promptly stash medication up and away from young children where it is out of their sight and reach to prevent poisoning.

In case of emergency/overdose

Call the poison control hotline at 1-800-222-1222 in the event of an overdose. Moreover, information can be found online at Call 911 right once if the person has collapsed, experienced a seizure, is having difficulty breathing, or cannot be roused.

Symptoms of overdose may include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Dizziness
  • Headache
  • Hearing ringing
  • Double or blurry vision
  • Confusion
  • Variations in heart rate
  • Having trouble breathing
  • Consciousness is lost
  • Seizures
  • Modifications to muscle reflexes
  • Inability to coordinate
  • Unusually giddy
  • Erratic thinking

What other information should I know?

Keep all of your appointments with your physician and the lab. To determine how well your body responds to quinidine and dextromethorphan, your doctor may request specific lab tests. Before and throughout your therapy, your doctor could also recommend an electrocardiogram (ECG), a test that examines the electrical activity in the heart.

No one else should take your medication. Any queries you may have regarding medication refills should be directed to your pharmacist.

You should keep a written record of every medication you take, including any over-the-counter (OTC) items, prescription drugs, and dietary supplements like vitamins and minerals. This list should be brought with you whenever you see a doctor or are admitted to the hospital. You should always have this information with you in case of emergencies.

Brand names

  • Nuedexta®
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