DEXTROMETHORPHAN–QUINIDINE

Class

• Noncompetitive NMDA receptor antagonist and sigma 1 agonist

DEXTROMETHORPHAN–QUINIDINE commonly prescribed for

(Bold for FDA approved)

How DEXTROMETHORPHAN–QUINIDINE works

• Dextromethorphan reduces glutamate neurotransmission through blocking NMDA receptors and by acting as an agonist at sigma 1 receptors</br>

• Dextromethorphan also has affinity for the serotonin transporter and may therefore modulate serotonin levels</br>

• Quinidine increases availability of dextromethorphan by inhibiting its metabolism via CYP2D6

How long until DEXTROMETHORPHAN–QUINIDINE works

• In clinical trials the rate of pseudobulbar affect episodes was significantly decreased beginning at day 15

Notable Side Effects

• Dizziness, asthenia

• Diarrhea, vomiting

• Cough, peripheral edema

• Urinary tract infection

• Euphoria

Life Threatening Side Effects

• Immune-mediated thrombocytopenia

• Hepatotoxicity

• Dose-dependent QTc prolongation

weight gain

unusual

sedation

unusual

What to do about DEXTROMETHORPHAN–QUINIDINE side effects

• Wait

• Wait

• Wait

• In a few weeks, switch to another agent or add other drugs

usual dosage range

• 20 mg/10 mg dextromethorphan/quinidine twice per day

Dosage Forms

• Capsule 20 mg/10 mg dextromethorphan/ quinidine

long term use

• Not evaluated

habit forming

• No

Renal Impairment

• Dose adjustment not necessary in patients with mild to moderate impairment

Hepatic Impairment

• Dose adjustment not necessary in patients with mild to moderate impairment

Cardiac Impairment

• Contraindicated in patients with a prolonged QTc interval, congenital long QTc syndrome, history suggestive of torsades de pointes, and heart failure

• Monitor ECG in patients with left ventricular hypertrophy or left ventricular dysfunctio

Elderly

• Some patients may tolerate lower doses better

Children and Adolescents

• Safety and efficacy have not been established

• Use with caution, observing for activation of known or unknown bipolar disorder and/or suicidal ideation, and strongly consider informing parents or guardian of this risk so they can help observe child or adolescent patients

Pregnancy

• Controlled studies have not been conducted in pregnant women

• Some animal studies have shown adverse effects

• Neurotoxicity findings were observed when dextromethorphan–quinidine was administered to juvenile rats on postnatal day 7, which corresponds to the third trimester of gestation through the first few months of life and may extend through the first 3 years of life in humans

Breast Feeding

• It is unknown if dextromethorphan– quinidine is secreted in human breast milk, but all psychotropics are assumed to be secreted in breast milk

• If the child becomes irritable or sedated, breast feeding or drug may need to be discontinued

• Must weigh benefits of breast feeding with risks and benefits of antidepressant treatment versus nontreatment to both the infant and the mother