Nuedexta (dextromethorphan Hbr/quinidine sulfate)

Dosages of dextromethorphan hydrobromide and quinidine sulfate in the commercially available fixed combination (Nuedexta(R)) are expressed in terms of the salts.

For the treatment of pseudobulbar affect (PBA) in adults, the recommended initial dosage of the fixed combination of dextromethorphan/quinidine is dextromethorphan hydrobromide 20 mg/quinidine sulfate 10 mg once daily for the first 7 days of therapy. On the eighth day of therapy and thereafter, dosage of the fixed combination should be increased to dextromethorphan hydrobromide 20 mg/quinidine sulfate 10 mg twice daily (every 12 hours). The need for continued treatment should be reassessed periodically since spontaneous improvement of PBA occurs in some patients.

Dosage of quinidine gluconate or quinidine sulfate for the treatment of arrhythmias usually is expressed in terms of the salt. Dosage of quinidine gluconate for the treatment of malaria is expressed in terms of the base or salt.

On a molar basis, approximately 267 mg of quinidine gluconate is equivalent to 200 mg of quinidine sulfate.

Dosage of quinidine must be carefully adjusted according to individual requirements and response, and the general condition and cardiovascular status of the patient.

Quinidine therapy should be initiated or quinidine dosage adjusted in a setting where facilities and personnel for patient monitoring and resuscitation are continuously available, especially if the drug is used in patients with known structural heart disease or other risk factors for toxicity.

ECG monitoring of cardiac function and determination of plasma quinidine concentrations are recommended during quinidine therapy, especially when the drug is given IV or when more than 2 g of oral quinidine sulfate is administered daily, and in patients with an increased risk of adverse reactions to quinidine, such as patients with severe heart disease, hypotension, or hepatic or renal disease.

Quinidine should be used for conversion of atrial fibrillation/flutter only after alternative measures (e.g., use of other drugs to control ventricular rate) have been inadequate. Quinidine should be discontinued if sinus rhythm is not restored within a reasonable amount of time.

Quinidine should be discontinued if QRS complex widens to 130% of its pretreatment duration, QTc interval widens to 130% of its pretreatment duration and is greater than 500 milliseconds, P waves disappear, or the patient develops clinically important tachycardia, symptomatic bradycardia, or hypotension.

For the treatment of severe malaria, the initial loading dose and continuous IV infusion rate of quinidine gluconate do not need to be reduced in patients with renal failure. If renal failure persists or clinical improvement does not occur in such patients, the maintenance infusion rate should be reduced by one-third to one-half on the third day of the quinidine gluconate infusion.

The commercially available fixed combination of dextromethorphan hydrobromide and quinidine sulfate (dextromethorphan/quinidine; Nuedexta(R)) is administered orally as capsules without regard to food.

Quinidine gluconate and quinidine sulfate are administered orally. Quinidine gluconate also is administered by IV infusion; IM administration is not recommended because absorption kinetics of the drug may vary depending on the patient's peripheral perfusion.

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There is no enhanced messaging for this drug.

There are no contraindication interactions for this drug.

There are no severe interactions for this drug.

There are no moderate interactions for this drug.

Because Nuedexta(R) contains quinidine, it should not be used concomitantly with other drugs containing quinidine, quinine, or mefloquine.

Dextromethorphan/quinidine is contraindicated in patients with a history of dextromethorphan/quinidine-, quinine-, mefloquine-, or quinidine-induced thrombocytopenia, hepatitis, bone marrow depression, or systemic lupus erythematosus-like syndrome. (See Thrombocytopenia and Other Hypersensitivity Reactions under Cautions: Warnings/Precautions.) Dextromethorphan/quinidine also is contraindicated in patients with known hypersensitivity to dextromethorphan (e.g., rash, urticaria).

Dextromethorphan/quinidine is contraindicated in patients receiving monoamine oxidase (MAO) inhibitors and in patients who have received MAO inhibitors within the preceding 14 days because of the risk of serious and possibly fatal drug interactions, including serotonin syndrome. At least 14 days should elapse between discontinuance of dextromethorphan/quinidine and initiation of MAO inhibitor therapy. (See Serotonin Syndrome under Cautions: Warnings/Precautions and also see Drug Interactions: Monoamine Oxidase Inhibitors.)

Dextromethorphan/quinidine is contraindicated in patients with a prolonged QT interval, congenital long QT syndrome, history suggestive of torsades de pointes, or heart failure.

Dextromethorphan/quinidine is contraindicated in patients with complete atrioventricular (AV) block without implanted pacemakers and in patients at high risk of complete AV block.

Dextromethorphan/quinidine is contraindicated in patients concomitantly receiving drugs that both prolong the QT interval and are metabolized by cytochrome P-450 (CYP) 2D6 (e.g., pimozide, thioridazine), since effects on the QT interval may be increased. (See Cardiac Effects under Cautions: Warnings/Precautions and also see Drug Interactions.)

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

There are no moderate contraindications for this drug.

Adverse effects occurring in at least 3% of patients receiving dextromethorphan/quinidine and with an incidence of at least twice that reported with placebo in short-term clinical studies in patients with amyotrophic lateral sclerosis or multiple sclerosis include diarrhea, dizziness, cough, vomiting, asthenia, peripheral edema, urinary tract infection, influenza, increased serum gamma-glutamyltransferase (gamma-glutamyltranspeptidase, GT, GGTP) concentrations, and flatulence. The most common adverse effects leading to discontinuance of dextromethorphan/quinidine include muscle spasticity, respiratory failure, abdominal pain, asthenia, dizziness, falls, and muscle spasms.

There are no severe adverse reactions for this drug.

There are no less severe adverse reactions for this drug.

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Safety and efficacy of dextromethorphan/quinidine have not been established in pediatric patients younger than 18 years of age. In addition, the pharmacokinetics of dextromethorphan/quinidine have not been studied in pediatric patients.

Category C. (See Users Guide.)

The effect of dextromethorphan/quinidine on labor and delivery is unknown.

Animal reproduction studies have not been performed to date with quinidine. It is not known whether quinidine can cause fetal harm when administered to pregnant women. Another cinchona alkaloid, quinine, has caused fetal blindness and has been implicated in congenital deafness. Quinidine should be used during pregnancy only when clearly needed. The safety of quinidine during labor and delivery is not known, but the drug exhibits oxytocic properties; the clinical importance remains to be established.

The manufacturer states that it is not known whether dextromethorphan and/or quinidine is distributed into human milk. Because many drugs are distributed into human milk, dextromethorphan/quinidine should be used with caution in nursing women.

Since quinidine is distributed into milk, the drug should be avoided, if possible, in nursing women.

In clinical trials with dextromethorphan/quinidine, 14% of patients were 65 years of age or older and 2% were 75 years of age or older. Clinical study of the fixed-dose combination did not include a sufficient number of patients 65 years of age or older to determine whether geriatric patients respond differently than younger adults.

The pharmacokinetics of dextromethorphan/quinidine have not been systematically evaluated in geriatric individuals older than 65 years of age, although such individuals were included in the clinical trial program. In a population pharmacokinetic analysis of patients receiving dextromethorphan hydrobromide 30 mg and quinidine sulfate 30 mg, similar pharmacokinetics were observed in individuals younger than 65 years of age and those 65 years of age or older.