Dextromethorphan and Quinidine (oral)

Dextromethorphan and quinidine (Nuedexta) is a combination drug used to treat pseudobulbar affect (PBA) or emotional incontinence, a rare nervous system disorder.


Dextromethorphan and quinidine is the first and only medicine approved by the US Food and Drug Administration (FDA) to treat pseudobulbar affect (PBA).

The central nervous system (brain, spinal cord, and optic nerves) controls thoughts, movements, and sensations. Patients with pseudobulbar affect (PBA) have a nervous system disorder which causes frequent laughing and crying spells that start suddenly and cannot be voluntarily controlled.

How dextromethorphan affects the brain in the treatment of PBA is not clearly known, but quinidine helps to keep dextromethorphan at the desired level in the body.

The two-drug therapy inhibits and controls the reflex to cry or laugh suddenly, thus reducing the frequency of the emotional episodes.

The medicine is supplied in the US under the brand name Nuedexta. It comes in the form of a capsule, is taken by mouth, and is available only by doctor's prescription.

Due to possible serious adverse effects, patients with certain medical problems or who use other medicines, including SSRI antidepressants, CNS depressants, and MAO inhibitors, should not be treated with this drug.

You should consider the potential benefits and risks of using dextromethorphan and quinidine.

Your doctor may help you decide if the medicine is safe for you, and determine how to treat you. Routine tests may be done before, during and after your treatment to ensure the medicine is safe for you, and your body's response to it.

You may be instructed to take an electrocardiogram (ECG) test. This test measures the electrical activity in the heart and may be done before and during your treatment.

Tell your doctor if you are allergic to the combination medicine or have had an unusual reaction to it. Some patients may also be allergic to inactive ingredients in the medication. Tell your doctor if you are allergic to mefloquine or using any product containing quinidine or quinine.

In discussing allergies, let your doctor know if you have any allergy to foods, preservatives, dyes or animals.

Certain medications or medical conditions may affect the way the tablet works. Let your doctor know if you have any other medical problems, and of all medications you are taking or plan to take. These include prescription and over-the-counter medicines (OTCs), vitamins, nutritional supplements, and herbal products.

Tell your doctor, especially if you are taking any serotonin reuptake inhibitors (SSRIs), such as fluoxetine, central nervous system (CNS) depressants, such as antihistamines or sedatives, or monoamine oxidase inhibitors (MAOIs), such as rasagiline.

Pediatrics and Geriatrics

The safety and efficacy of using dextromethorphan and quinidine in children and elderly patients have not been established.


Adequate studies have not been done to determine the safety and efficacy of using the drug in pregnant women.


There is a possibility of minimal risk to a breastfeeding infant since the medicine may pass to the child through breast milk.

Your doctor may take necessary precautions where the safety and efficacy (or the risks) of using the medicine in certain patients have not been established.

Condition treated

  • Pseudobulbar Affect (PBA)

Type Of Medicine

  • Central Nervous System (CNS) agent + Antiarrhythmic agent

Side Effects

This combination drug may cause side effects that may be mild or severe. Some of them may be serious and require immediate or urgent medical attention.

Call your doctor right away if you notice any of the following symptoms. They may be signs of a serious side effect:

  • Rash
  • Hoarseness
  • Unusual bruising or bleeding
  • Muscle pain
  • Fast heart beat
  • Trouble breathing
  • Fainting
  • Swelling of the face, lips, tongue or throat
  • Swollen lymph nodes
  • Lightheadedness

The following other symptoms may not occur frequently in patents, but if they do, they require immediate medical attention. Call your doctor right away if you experience any of them.

Less commonly occur

  • Sweating
  • Diarrhea
  • Vomiting
  • Pain in the bladder
  • Dry eyes or mouth
  • Cough
  • Shivering
  • Chills
  • Loss of appetite
  • Fever
  • Joint pain
  • Nausea
  • Headache
  • Pain in the back or lower side
  • Urine that is cloudy or bloody
  • Urine that has a strong smell
  • Frequent urge to urinate
  • Tingling of the hands or feet
  • General feeling of illness or discomfort
  • Tiredness or weakness that is not usual
  • Muscle aches and pains
  • Runny nose
  • Sore throat
  • Muscle spasms
  • Trouble sleeping
  • Sense of burning or pain while urinating
  • Rapid or unusual weight gain or loss
  • Swelling or bloating of the face, hands, arms, lower legs or feet

Some side effects that may occur usually do not need medical attention. They generally go away on their own as the body gets used to the medicine. If they become bothersome or do not go away, speak with your doctor.

Less commonly occur

  • Feeling bloated
  • Passing gas
  • Lack or loss of energy or strength
  • Excess gas or air in the stomach or intestines
  • Feeling of fullness in the stomach

These are not all the possible side effects, and all of them may not occur in one single patient. If you experience other side effects or any usual symptom, talk to your doctor or healthcare professional.

You can ask them about ways to reduce or prevent side effects. You may also call the FDA at 1-800-FDA-1088 to report side effects.


Dosage may vary from patient to patient. Your doctor will decide your dose. Special directions will be given on the prescription label. Follow them and any other given by your doctor or pharmacist.

The label should tell you the amount and strength of each dose, how often you should take it, time between each dose, and the duration of your treatment.

For treating PBA or emotional incontinence

The medicine comes as a capsule that contains 20 milligrams (mg) of dextromethorphan and 10 mg of quinidine. You may take your capsule with water, but not grapefruit juice.

Adults: Take 1 capsule once a day for the first 7 days of treatment. On day 8, you should take 2 capsules per day (take one capsule every 12 hours). Continue with the 2 capsules per day dosage until your treatment ends.

Children: Your doctor may determine if, and how, to treat you.

Missed dose

If you miss a dose of your medicine, take it as soon as possible. If it is almost time to take your next dose, skip the missed dose and take your next dose on schedule. Do not take an extra dose to make up for a missed dose.


The following are symptoms of overdose. Call 911 for emergency medical care right away.

  • Sweating
  • Agitation
  • Depression
  • Blurred vision
  • Pain or discomfort in the chest
  • Confusion (e.g., as to time, place, or people)
  • Lightheadedness or dizziness (including when getting up suddenly from a sitting or lying position)
  • Ringing, buzzing or other noise in the ear that is continuous
  • Lack of awareness
  • Reduced responsiveness
  • Difficulty seeing at night
  • Double vision
  • Behavior that is aggressive or violent
  • Unusual excitement
  • Fainting
  • Heartbeat or pulse that is irregular, fast or pounding
  • Feeling as if you or your surroundings are moving
  • Loss of hearing
  • Severe sleepiness
  • Feeling restless
  • Unable to move the eyes
  • Eyes become highly sensitive to sunlight
  • Irregular or slow heart rate
  • Loss of consciousness
  • Shaking or trembling
  • Overactive reflexes
  • Poor coordination
  • Unusual facial expressions
  • Seeing 'œdouble'
  • Change in color of vision
  • Seizures
  • Uncontrollable blinking or spasm of the eyelids
  • Change in consciousness
  • Spinning sensation
  • Shakiness or unsteadiness when walking or other movements
  • Delusions
  • Hallucinations
  • Shivering
  • Shortness of breath
  • Uncontrollable sticking out of tongue
  • Talking or behaving with excitement you cannot control
  • Trouble breathing, swallowing or speaking
  • Unable to control eye movements
  • Twisting movements of the neck, arms, legs, or trunk of the body that cannot be controlled
  • Lack of muscle control or coordination
  • Unusual excitement, nervousness or restlessness
  • Twitching


Other medicines

Tell your doctor of all medicines (whether prescription or over-the-counter) and health products you use or plan to use. They may affect the combination drug treatment and even cause serious adverse interaction.

The following medicines have the potential to cause significant interaction with dextromethorphan and quinidine. Their use is not recommended during treatment.

Your doctor may go ahead and treat you, but may change some of the other medicines you take or adjust their dosage.

  • Vernakalant
  • Thioridazine
  • Bepridil
  • Tranylcypromine
  • Mesoridazine
  • Colchicine
  • Dronedarone
  • Voriconazole
  • Fingolimod
  • Grepafloxacin
  • Itraconazole
  • Ketoconazole
  • Amisulpride
  • Levomethadyl
  • Posaconazole
  • Mifepristone
  • Aurothioglucose
  • Isocarboxazid
  • Moclobemide
  • Pimozide
  • Cisapride
  • Sparfloxacin
  • Ziprasidone
  • Nelfinavir
  • Ritonavir
  • Amifampridine
  • Nialamide
  • Iproniazid
  • Procarbazine
  • Saquinavir
  • Clorgyline
  • Selegiline
  • Phenelzine
  • Terfenadine
  • Rasagiline
  • Fluconazole
  • Tipranavir
  • Piperaquine
  • Toloxatone
  • Pargyline

The following medicines are not usually recommended during your treatment. If to maintain your health it is necessary to use any of them, your doctor may change your dose or how often you take your medicines.

  • Goserelin
  • Isavuconazonium Sulfate
  • Acetazolamide
  • Donepezil
  • Ajmaline
  • Vilazodone
  • Alfuzosin
  • Amiodarone
  • Vincristine Sulfate Liposome
  • Amitriptyline
  • Enzalutamide
  • Amprenavir
  • Ciprofloxacin
  • Arbutamine
  • Dasabuvir
  • Artemether
  • Chloral Hydrate
  • Astemizole
  • Bedaquiline
  • Blinatumomab
  • Anagrelide
  • Brexpiprazole
  • Vandetanib
  • Buprenorphine
  • Azithromycin
  • Bupropion
  • Telaprevir
  • Golimumab
  • Buserelin
  • Ceritinib
  • Isoflurane
  • Chloroquine
  • Almotriptan
  • Citalopram
  • Arsenic Trioxide
  • Cobicistat
  • Lidocaine
  • Boceprevir
  • Crizotinib
  • Dabigatran Etexilate
  • Alefacept
  • Dabrafenib
  • Levofloxacin
  • Decamethonium
  • Prochlorperazine
  • Degarelix
  • Aprindine
  • Deslorelin
  • Cyclobenzaprine
  • Desvenlafaxine
  • Afatinib
  • Digitoxin
  • Halothane
  • Digoxin
  • Nortriptyline
  • Dofetilide
  • Ondansetron
  • Apomorphine
  • Doxepin
  • Methylene Blue
  • Doxorubicin
  • Topotecan
  • Atracurium
  • Droperidol
  • Ombitasvir
  • Duloxetine
  • Eliglustat
  • Delamanid
  • Escitalopram
  • Dasatinib
  • Etravirine
  • Fentanyl
  • Darunavir
  • Flecainide
  • Trifluoperazine
  • Foscarnet
  • Gatifloxacin
  • Clomipramine
  • Gemifloxacin
  • Desipramine
  • Isradipine
  • Granisetron
  • Halofantrine
  • Domperidone
  • Clozapine
  • Hydroxychloroquine
  • Dolasetron
  • Hydroxytryptophan
  • Conivaptan
  • Efavirenz
  • Hydroxyzine
  • Ibutilide
  • Delavirdine
  • Idelalisib
  • Erythromycin
  • Imipramine
  • Aripiprazole
  • Infliximab
  • Fluoxetine
  • Ivabradine
  • Lapatinib
  • Disopyramide
  • Nilotinib
  • Leuprolide
  • Conadorelin
  • Levomilnacipran
  • Histrelin
  • Lidoflazine
  • Tetrabenazine
  • Lorcainide
  • Mexiletine
  • Lumefantrine
  • Sertraline
  • Hydroquinidine
  • Mefloquine
  • Haloperidol
  • Meperidine
  • Linezolid
  • Metronidazole
  • Venetoclax
  • Mirtazapine
  • Doxorubicin Hydrochloride Liposome
  • Morphine
  • Panobinostat
  • Morphine Sulfate Liposome
  • Nafarelin
  • Palonosetron
  • Salmeterol
  • Nalidixic Acid
  • Siltuximab
  • Lopinavir
  • Enflurane
  • Norfloxacin
  • Lumacaftor
  • Octreotide
  • Moxifloxacin
  • Ofloxacin
  • Spiramycin
  • Oxycodone
  • Lanreotide
  • Paliperidone
  • Vasopressin
  • Pancuronium
  • Methadone
  • Paroxetine
  • Memantine
  • Pimavanserin
  • Fosamprenavir
  • Pirmenol
  • Ziprasidone
  • Pixantrone
  • Lorcaserin
  • Prilocaine
  • Tubocurarine
  • Procainamide
  • Milnacipran
  • Telithromycin
  • Propafenone
  • Quetiapine
  • Nebivolol
  • Perflutren Lipid Microsphere
  • Quinidine
  • Ranolazine
  • Secukinumab
  • Protriptyline
  • Sibutramine
  • Probucol
  • Sodium Phosphate
  • Pazopanib
  • Sodium Phosphate, Dibasic
  • Pentamidine
  • Sorafenib
  • Vincristine
  • Sulfamethoxazole
  • Quinine
  • Sulpiride
  • Pasireotide
  • Sunitinib
  • Pitolisant
  • Telavancin
  • Sodium Phosphate, Monobasic
  • Tizanidine
  • Eluxadoline
  • Solifenacin
  • Toremifene
  • Sotalol
  • Trazodone
  • Simeprevir
  • Atazanavir
  • Trimethoprim
  • Paritaprevir
  • Triptorelin
  • Ulipristal
  • Vardenafil
  • Sevoflurane
  • Vecuronium
  • Amoxapine
  • Tacrolimus
  • Vemurafenib
  • Fluvoxamine
  • Tramadol
  • Venlafaxine
  • Trimipramine
  • Vinflunine
  • Asenapine
  • Clarithromycin
  • Vortioxetine
  • Zolmitriptan
  • Succinylcholine
  • Zuclopenthixol

The risk of certain side effects may increase if the following medicines are used during your treatment, but using them may be best for your health.

If prescribed together, your doctor may take the necessary precautions to ensure all your medicines are used in a safe and effective manner.

  • Nifedipine
  • Tolterodine
  • Abiraterone
  • Baroxetine
  • Clobazam
  • Magnesium Oxide
  • Dicumarol
  • Galantamine
  • Verapamil
  • Haloperidol
  • Amiloride
  • Magnesium Hydroxide
  • Atenolol
  • Nisoldipine
  • Dalfopristin
  • Quinupristin
  • Phenobarbital
  • Abarelix
  • Phenytoin
  • Magaldrate
  • Cimetidine
  • Propranolol
  • Quinidine
  • Fosphenytoin
  • Rifapentine
  • Magnesium Trisilicate
  • Tramadol
  • Dextromethorphan
  • Magnesium Carbonate

MAO inhibitors

The drug should not be used in patients who used an MAO inhibitor (MAOI), such as rasagiline or phenelzine, within the past 14 days. Your doctor may decide to treat you but may change the doses of your medications. You may also be closely monitored for side effects.

Patients who stopped using dextromethorphan and quinidine should wait until at least 14 days have passed before they start using MAOIs.

Serotonin Syndrome

Patients may experience a serious side effect known as 'œserotonin syndrome' if they use this drug with SSRI medicines, such as fluoxetine, or tricyclic antidepressants, such as imipramine.

Symptoms include heavy sweating, confusion, shivering, and restlessness and may require urgent medical care.

Interaction with other medicines not listed here may occur.

Your doctor may tell you about other medications you should avoid.

Other interactions

Food, alcohol, and tobacco

Dextromethorphan and quinidine may be taken with or without food. Ask your doctor about any restriction on types of foods or drinks. Your doctor may also warn you about the use of alcohol or tobacco during your treatment.

Alcohol may add to the effects of this PBA drug and increase dizziness or drowsiness.

The following beverage should not be used with your medicine. If it is necessary to use it, your doctor may give you special instructions on how to do so.

  • Grapefruit Juice

Other Medical Problems

It may not be safe to use this drug to treat patients who have other medical problems.

Patients who have (or have a history of) the following conditions that were caused by using mefloquine, quinidine or quinine should not use this medicine. Tell your doctor if you have any of them:

  • Hepatitis
  • Bone marrow problems
  • Lupus-like syndrome

The medicine should also not be used in patients with the following other conditions:

  • Heart block without a pacemaker
  • Heart rhythm problems such as congenital long QT syndrome

The medicine may increase the risk of other serious side effects in patients with the following conditions:

  • Low potassium in the blood (Hypokalemia)
  • Low magnesium in the blood (Hypomagnesemia)
  • Heart or blood vessel disease

An increased risk of serious side effects may occur in the following patients because the medicine takes a longer time to leave their body.

  • Kidney disease (severe)

The medicine should be used with caution in patients with the following condition, since it may make the condition worse:

Dependence may more likely occur in the following patients:

  • Drug abuse or drug-dependent patients (or those with a history of)

Interaction with other medical problems not listed here may occur. Ask your doctor for more information.


  • Use dextromethorphan and quinidine only if your doctor prescribed it for you for treating PBA.
  • Do not share the medicine with anyone else even if they have similar symptoms.
  • Do not use this medicine together with other products containing mefloquine, quinidine or quinine.
  • Do not use this medicine if you used an MAO inhibitor (MAOI), such as rasagiline, within the past 14 days.
  • Do not use an MAO inhibitor (MAOI) until at least 14 days have passed since you stopped using dextromethorphan and quinidine.
  • This medicine may cause dizziness or coordination problems. To avoid injury to yourself or others, ensure you know how the medicine affects you before you drive or use machines.
  • Do not take other medicines, change your dose or stop your treatment unless your doctor approves of it.
  • Avoid using alcohol, or drugs that cause drowsiness. They may increase the risk of side effects. These drugs include serotonin reuptake inhibitors (SSRIs), such as fluoxetine, and central nervous system (CNS) depressants, such as antihistamines or sedatives.
  • Before having any surgery, including a dental procedure, tell the person performing the procedure that you are taking dextromethorphan and quinidine.
  • Take your dosage exactly as scheduled. If your PBA symptoms do not lessen or they become worse, tell your doctor.
  • Keep all appointments to follow up with your doctor. Regular follow-up visits and lab tests may be required for your doctor to check to see how your body is responding to the medication. Your doctor may also need to adjust your treatment plan, as necessary.


Store the medicine in a closed container at room temperature. Avoid exposure to heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Throw away medicine that expired or is no longer needed. Ask your healthcare professional or local waste disposal agency how to safely dispose of it.


Dextromethorphan and quinidine is the first and only drug approved by the FDA for treating pseudobulbar affect (PBA) or emotional incontinence. This new drug treats this rare condition which affects approximately 2 million people in the US.

There is a long list of drugs that have the potential to cause significant interaction with this combination medicine.

Using the drug with antimalarial agents such as mefloquine and quinine or antiarrhythmic agents such as quinidine can cause serious adverse effects. This may happen particularly in patients with bone marrow problems or hepatitis.

Serious adverse interaction is known to occur when it is used with MAO inhibitors or CNS depressants. Used with SSRIs, such as fluoxetine, this drug can cause a serious condition called serotonin syndrome.

The medicine proves to be effective in reducing the number of daily involuntary laughing and crying spells in PBA patients. However, clinical studies conducted are not precisely clear on how it affects the nervous system to produce the desired relief.