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.
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.
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:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:
The medicine should also not be used in patients with the following other conditions:
The medicine may increase the risk of other serious side effects in patients with the following conditions:
An increased risk of serious side effects may occur in the following patients because the medicine takes a longer time to leave their body.
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:
Interaction with other medical problems not listed here may occur. Ask your doctor for more information.
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.