Dextromethorphan and quinidine

Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medication.

Unless your doctor tells you otherwise, continue your normal diet.

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 in people with certain heart rhythm disorders.

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.

You should not take this medicine if you are allergic to dextromethorphan or quinidine, or if you have:

• heart failure;

• a history of life-threatening heart rhythm disorder;

• a serious heart condition called "AV block" (unless you have a pacemaker);

• a history of Long QT syndrome; or

• if you are also taking mefloquine, quinidine, or quinine.

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.

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:

• low levels of platelets in your blood;

• hepatitis;

• bone marrow suppression; or

• lupus-like symptoms (joint pain, fever, headaches, numbness or cold feeling in your fingers or toes).

Some medicines can cause unwanted or dangerous effects when used with dextromethorphan and quinidine. Your doctor may need to change your treatment plan if you use any of the following drugs:

• tamoxifen;

• certain antidepressants--amitriptyline, clomipramine, desipramine, fluoxetine, paroxetine, sertraline, venlafaxine;

• certain heart rhythm medications--amiodarone, flecainide, procainamide, propafenone; or

• certain medicines to treat psychiatric disorders--chlorpromazine, haloperidol, perphenazine, pimozide, quetiapine, risperidone, thioridazine.

To make sure dextromethorphan and quinidine is safe for you, tell your doctor if you have:

• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood);

• heart disease, high blood pressure, coronary artery disease;

• slow heartbeats or any type of heart rhythm disorder;

• myasthenia gravis;

• bladder obstruction or other urination problems; or

• blockage in your digestive tract (stomach or intestines).

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.

It is not known whether dextromethorphan and quinidine passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

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

Usual Adult Dose for Pseudobulbar Affect:

-Initial Dose: Days 1 to 7: Dextromethorphan 20 mg-quinidine 10 mg orally once a day
-Maintenance Dose: Day 8 and thereafter: Dextromethorphan 20 mg-quinidine 10 mg orally every 12 hours
-Maximum dose: Dextromethorphan 40 mg-quinidine 20 mg orally per day

Comments: The need for continued treatment should be reassessed periodically as spontaneous improvement of PBA occurs in some patients.

Use: Treatment of Pseudobulbar Affect (PBA)

• It is used to treat sudden laughing and/or crying that happens without your control.

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Hypersensitivity to dextromethorphan, quinidine, quinine, mefloquine, or any component of the formulation; concomitant use with quinidine or other medications containing quinidine, quinine, or mefloquine; history of quinine-, mefloquine-, or quinidine-induced thrombocytopenia, hepatitis, bone marrow depression, or lupus-like syndrome; concurrent administration with or within 2 weeks of discontinuing an MAO inhibitor; patients with prolonged QT interval, congenital QT syndrome, or history of torsade de pointes; patients with heart failure; concurrent use of drugs that prolong the QT interval and are metabolized by CYP2D6 (eg, pimozide, thioridazine); patients with complete atrioventricular (AV) block without an implanted pacemaker or patients at high risk of complete AV block

Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

See individual agents.

QT interval at baseline and 3 to 4 hours after the first dose in patients at risk for QTc prolongation; potassium and magnesium prior to and during therapy; CBC, liver and renal function tests; periodically assess risk factors for arrhythmias during treatment; periodically reassess the need for treatment (spontaneous improvement of PBA may occur); worsening myasthenia gravis or other sensitive conditions due to anticholinergic effects.

-Mild Hepatic Impairment (Child-Pugh A): No adjustment recommended.
-Moderate Hepatic Impairment (Child-Pugh B): No adjustment recommended.
-Severe Hepatic Impairment (Child-Pugh C): Data not available; however, increases in dextromethorphan and/or quinidine levels are likely to be observed.

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.