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dextromethorphan and quinidine

Pronunciation: DEX troe meth OR fan and KWIN i deen

Brand: Nuedexta

What is the most important information I should know about dextromethorphan and quinidine?

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You should not take dextromethorphan and quinidine if you are also taking quinidine (Quin-G), quinine (Qualaquin), or mefloquine (Lariam), or if you have ever had an allergic reaction or serious medical problem caused by taking any of these medications.

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You should not use this medication if you are allergic to dextromethorphan or quinidine, or if you have heart failure, a serious heart condition called "AV block" (unless you have a pacemaker), or a history of Long QT syndrome or life-threatening heart rhythm disorder.

Before you take this medication, tell your doctor if you have slow heartbeats or any other type of heart rhythm disorder, an electrolyte imbalance, bladder or bowel obstruction, myasthenia gravis, or a family history of Long QT syndrome.

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There are many other drugs that can cause serious or life threatening medical problems if you take them together with dextromethorphan and quinidine. Tell your doctor about all other medicines you use. Do not start a new medication without telling your doctor.

What is dextromethorphan and quinidine?

Dextromethorphan affects the signals in the brain that trigger cough reflex and is generally used as a cough suppressant.

Quinidine affects the way that the heart beats and is generally used to in people with certain heart rhythm disorders.

The combination of dextromethorphan and quinidine is used to treat involuntary outbursts of crying or laughing in people with certain neurological disorders, including multiple sclerosis and amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease).

Dextromethorphan and quinidine may also be used for purposes not listed in this medication guide.

What should I discuss with my healthcare provider before taking dextromethorphan and quinidine?

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You should not take this medicine if you are also taking quinidine (Quin-G), quinine (Qualaquin), or mefloquine (Lariam), or if you have ever had hepatitis, low levels of platelets in your blood, bone marrow depression, lupus-like syndrome, or an allergic reaction caused by taking any of these medications.

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You should not use this medication if you are allergic to dextromethorphan or quinidine, or if you have:

  • heart failure;
  • a history of life-threatening heart rhythm disorder;
  • a history of Long QT syndrome; or
  • a serious heart condition called "AV block" (unless you have a pacemaker).
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Do not use dextromethorphan and quinidine if you have used an MAO inhibitor such as furazolidone (Furoxone), isocarboxazid (Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam, Zelapar), or tranylcypromine (Parnate) in the last 14 days. A dangerous drug interaction could occur, leading to serious side effects.

After you stop taking dextromethorphan and quinidine, you must wait at least 14 days before you start taking an MAOI.

There are many other drugs that can cause serious or life threatening medical problems if you take them together with dextromethorphan and quinidine. The following drugs should not be used while you are taking dextromethorphan and quinidine:

  • an anti-malaria drug called chloroquine (Aralen);
  • certain antidepressants: amitriptyline (Elavil, Vanatrip, Limbitrol), clomipramine (Anafranil), or desipramine (Norpramin);
  • certain heart rhythm medications: quinidine (Quin-G), procainamide (Procan, Pronestyl), or propafenone, (Rythmol); or
  • certain medicines to treat psychiatric disorders: chlorpromazine (Thorazine), haloperidol (Haldol), pimozide (Orap), or thioridazine (Mellaril).
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If you cannot avoid taking any of the medicines listed above, your heart function may need to be tested on a regular basis while you are taking dextromethorphan and quinidine. Do not miss any follow-up visits to your doctor.

To make sure you can safely take this medicine, tell your doctor if you have any of these other conditions:

  • a family history of Long QT syndrome;
  • an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);
  • slow heartbeats or any type of heart rhythm disorder;
  • myasthenia gravis;
  • bladder obstruction or other urination problems; or
  • a bowel obstruction or intestinal disorder.
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FDA pregnancy category C. It is not known whether dextromethorphan and quinidine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication.

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It is not known whether this medication passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

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Do not give dextromethorphan and quinidine to anyone under 18 years old without medical advice.

How should I take dextromethorphan and quinidine?

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.

Dextromethorphan and quinidine is usually started at a dose of 1 capsule per day for 7 days. After the first week you will take 1 capsule every 12 hours. Follow your doctor's instructions. Do not take more than 2 capsules in a 24-hour period.

You may take dextromethorphan and quinidine with or without food.

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Your doctor will need to check your progress on a regular basis. This will help your doctor determine how long to treat you with dextromethorphan and quinidine. To be sure the medicine not causing harmful effects, your heart function may need to be checked using an electrocardiograph or ECG (sometimes called an EKG). This machine measures electrical activity of the heart. Visit your doctor regularly.

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Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

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Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose can cause severe dizziness, confusion, double vision, ringing in your ears, vomiting, rapid heart rate, weak or shallow breathing, a dazed feeling, or seizure (convulsions).

What should I avoid while taking dextromethorphan and quinidine?

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Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Grapefruit and grapefruit juice may interact with dextromethorphan and quinidine and lead to potentially dangerous effects. Discuss the use of grapefruit products with your doctor.

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Ask a doctor or pharmacist before using any cough or cold medication. Dextromethorphan is contained in many combination medicines. Taking certain products together can cause you to get too much dextromethorphan. Check the label to see if a medicine contains dextromethorphan (Delsym, Robitussin Maximum Strength, Vicks 44, and others).

What are the possible side effects of dextromethorphan and quinidine?

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Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

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Stop using dextromethorphan and quinidine and call your doctor at once if you have a serious side effect such as:

  • severe dizziness, fainting, fast or pounding heartbeat;
  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin;
  • pain or burning when you urinate;
  • fever, chills, flu symptoms, nausea, vomiting, feeling light-headed;
  • nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
  • agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting; or
  • joint pain or swelling with fever, swollen glands, muscle aches, nausea, vomiting, chest pain, unusual thoughts or behavior, and/or seizure (convulsions).

Less serious side effects may include:

  • diarrhea, gas, mild stomach pain;
  • muscle spasm;
  • dizziness, weakness;
  • cough; or
  • swelling in your hands or feet.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect dextromethorphan and quinidine?

Tell your doctor about all other medicines you use, especially:

  • aprepitant (Emend);
  • cimetidine (Tagamet);
  • digoxin (Lanoxin, Lanoxicaps);
  • narcotic cough medicine (codeine or dihydrocodeine);
  • ADHD medication such as atomoxetine (Strattera), dextroamphetamine (Adderall), methamphetamine (Desoxyn), methylphenidate (Ritalin, Daytrana, Metadate, Concerta);
  • an antidepressant such as amitriptyline (Elavil, Vanatrip, Limbitrol), citalopram (Celexa), desipramine (Norpramin), doxepin (Sinequan), duloxetine (Cymbalta), fluoxetine (Prozac, Sarafem, Symbyax), nortriptyline (Pamelor), nefazodone, paroxetine (Paxil), sertraline (Zoloft), or venlafaxine (Effexor);
  • an antibiotic such as clarithromycin (Biaxin), dalfopristin/quinupristin (Synercid), doxycycline (Doryx, Oracea, Periostat, Vibramycin), erythromycin (E.E.S., EryPed, Ery-Tab, Erythrocin, Pediazole), metronidazole (Flagyl), norfloxacin (Noroxin), telithromycin (Ketek), or tetracycline (Ala-Tet, Brodspec, Panmycin, Sumycin, Tetracap);
  • antifungal medicine such as fluconazole (Diflucan), itraconazole (Sporanox), ketoconazole (Nizoral), miconazole (Oravig), or voriconazole (Vfend);
  • cancer medicine such as doxorubicin (Adriamycin, Doxil), lomustine (CeeNU), tamoxifen (Soltamox);
  • heart or blood pressure medication such as amiodarone (Cordarone, Pacerone), betaxolol (Kerlone), captopril (Capoten), carvedilol (Coreg), diltiazem (Cartia, Cardizem), flecainide (Tambocor), labetalol (Normodyne), metoprolol (Dutoprol, Lopressor, Toprol), mexilitene (Mexitil), nicardipine (Cardene), pindolol (Visken), propranolol (Inderal), timolol (Blocadren), verapamil (Calan, Covera, Isoptin, Verelan), and others;
  • HIV/AIDS medicine such as atazanavir (Reyataz), delavirdine (Rescriptor), efavirenz (Sustiva, Atripla), fosamprenavir (Lexiva), indinavir (Crixivan), nelfinavir (Viracept), saquinavir (Invirase), or ritonavir (Norvir, Kaletra); or
  • pain medication such as codeine (Tylenol #3), hydrocodone (Lortab, Vicodin, Vicoprofen), oxycodone (OxyContin, Percocet), or tramadol (Ultram, Ultracet).

This list is not complete and there are many other drugs that can interact with dextromethorphan and quinidine. Tell your doctor about all medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor. Keep a list of all your medicines and show it to any healthcare provider who treats you.

Where can I get more information?

Your pharmacist can provide more information about dextromethorphan and quinidine.


Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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