dextromethorphan and quinidine

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

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

Tell your doctor about all your current medicines and any you start or stop using. Many drugs can interact, and some drugs should not be used together.

What is dextromethorphan and quinidine?

Dextromethorphan and quinidine is a combination medicine 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?

• heart failure;
• a history of life-threatening heart rhythm disorder;
• long QT syndrome (in you or a family member);
• a serious heart condition called "AV block" (unless you have a pacemaker); or
• if you also use mefloquine, quinidine, or quinine.

You also should not take dextromethorphan and quinidine if you have ever had any of the following problems caused by taking mefloquine, quinidine, or quinine:

• bruising or bleeding;
• hepatitis;
• an allergic reaction; or
• lupus-like symptoms (joint pain, fever, skin rash on your cheeks).

Do not use dextromethorphan and quinidine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others. After you stop taking dextromethorphan and quinidine, you must wait at least 14 days before you start taking an MAOI.

Be sure your doctor knows if you also take stimulant medicine, opioid medicine, herbal products, or medicine for depression, mental illness, Parkinson's disease, migraine headaches, serious infections, or prevention of nausea and vomiting. These medicines may interact with dextromethorphan and quinidine and cause a serious condition called serotonin syndrome.

Tell your doctor if you have ever had:

• heart disease, high blood pressure, coronary artery disease;
• slow heartbeats or any type of heart rhythm disorder;
• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);
• myasthenia gravis; or
• trouble with balance or walking.

Tell your doctor if you are pregnant or breastfeeding.

How should I take dextromethorphan and quinidine?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Dextromethorphan and quinidine is usually taken once per day for 7 days, and then once every 12 hours. Follow your doctor's dosing instructions very carefully.

You may take dextromethorphan and quinidine with or without food.

Your doctor will need to check your progress on a regular basis. You may need medical tests to help your doctor determine how long to treat you with dextromethorphan and quinidine.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Do not take more than 2 capsules in a 24-hour period.

What happens if I overdose?

Overdose can cause severe dizziness, confusion, double vision, ringing in your ears, hearing loss, vomiting, fast or irregular heart rate, weak or shallow breathing, or seizure (convulsions).

What should I avoid while taking dextromethorphan and quinidine?

Grapefruit may interact with dextromethorphan and quinidine and lead to unwanted side effects. Avoid the use of grapefruit products.

What are the possible side effects of dextromethorphan and quinidine?

• fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);
• easy bruising or bleeding (nosebleeds, bleeding gums);
• pain or burning when you urinate;
• liver problems --fever, right-sided upper stomach pain, vomiting, loss of appetite, yellowing of your skin or eyes, and not feeling well; or
• lupus-like symptoms --muscle or joint pain, flu symptoms, chest pain, and a rash or patchy skin color that worsens in sunlight.

Common side effects may include:

• dizziness, weakness;
• diarrhea, gas, vomiting;
• swelling in your hands or feet;
• flu symptoms, cough; or
• abnormal liver function tests.

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?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Many drugs can affect dextromethorphan and quinidine, and some drugs should not be used at the same time. Tell your doctor about all your current medicines and any medicine you start or stop using. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here.

Where can I get more information?

Your pharmacist can provide more information about dextromethorphan and quinidine.