Classes
DEA Class; Rx
Common Brand Names; Nuedexta
- NMDA Antagonists
Description
Oral combination of dextromethorphan and low-dose quinidine.
Used for pseudobulbar affect (PBA); quinidine, a 2D6 inhibitor, increases the bioavailability of dextromethorphan, the active entity.
Due to the potential for quinidine to cause QT prolongation, contraindications apply to patients with certain cardiac conditions or those receiving medications that both prolong the QT interval and are CYP2D6 substrates (e.g., pimozide).
Indications
Indicated for PBA and symptoms associated with a variety of neurological conditions (eg, MS, ALS) that result in involuntary, sudden, and frequent episodes of laughing and/or crying
PBA occurs secondary to a variety of otherwise unrelated neurologic conditions, and is characterized by involuntary, sudden, and frequent episodes of laughing and/or crying; episodes typically occur out of proportion or incongruent to the underlying emotional state
PBA is a specific condition, distinct from other types of emotional lability that may occur in patients with neurological disease or injury
Contraindications
Hypersensitivity
History of quinine, mefloquine, or quinidine-induced thrombocytopenia, hepatitis, bone marrow depression, or lupus-like syndrome
Concomitant use with drugs containing quinidine, quinine, or mefloquine
Coadministration of MAOIs or use within 14 d
Drugs that both prolong QT interval and are metabolized by CYP2D6 (eg, thioridazine, pimozide)
Complete AV block (without implanted pacemakers)
Prolonged QT interval, congenital long QT syndrome, or history of torsades de pointes or heart failure
Adverse Effects
Diarrhea (13%)
Dizziness (10%)
Cough (5%)
Vomiting (5%)
Asthenia (5%)
Peripheral edema (5%)
Increased gamma-glutamyltransferase (3%)
Flatulence (3%)
Warnings
Quinidine can cause immune-mediated thrombocytopenia (discontinue if thrombocytopenia occurs)
Hepatotoxicity reported within first few weeks following initiation of quinidine
Monitor for QTc prolongation if concomitant use of drugs taht prolong QT interval cannot be avoided or concomitant CYP3A4 used
Quinidine may cause anticholinergic effects and exacerbate certain conditions (eg, myasthenia gravis)
Monitor ECG in patients with left ventricular hypertrophy or left ventricular dysfunction
Dextromethorphan may cause serotonergic effects; monitor for worsening in myasthenia gravis and other sensitive conditions
Use caution with CYP2D6 poor metabolizers
CYP3A4 inhibitors may increase quinidine serum levels and risk for QT prolongation
Coadministration with CYP2D6 substrates other than dextromethorphan that cause accumulation of parent drug and/or failure of metabolite formation may decrease safety and/or efficacy of concomitant CYPD6 metabolized drugs; adjust dose of CYPD6 substrate or use alternative therapy when indicated
Concomitant use of dextromethorphan with serotonergic drugs (eg, SSRIs, TCAs) may increase risk for serotonin syndrome
Quinidine may increase digoxin levels (as much as double) by inhibiting P-glycoprotein
Coadministration with alcohol or other CNS depressants may cause additive effects
May cause dizziness; use precautions to reduce falls
Pregnancy and Lactation
There are no adequate data on the developmental risk associated with use in pregnant women
Quinidine is excreted in human milk; unknown whether dextromethorphan is excreted in human milk
Maximum Dosage
Quinidine has a narrow therapeutic index (serum concentration range: 2—6 mcg/ml). Dosage is individualized based on patient weight, age, renal and hepatic function, clinical goals, patient response, and serum quinidine concentrations.
How supplied
Dextromethorphan/quinidine
capsule
- 20mg/10mg
