(continued) DEXTROMETHORPHAN
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psychotropics assumed to be secreted in
breast milk
• If child becomes irritable or sedated,
breast feeding or drug may need to be
discontinued
• Must weigh benefi ts of breast feeding
with risks and benefi ts of antidepressant
treatment versus nontreatment to both the
infant and the mother
SPECIAL POPULATIONS
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 prolonged
QT interval, congenital long QT syndrome,
history suggestive of torsades de pointes,
and heart failure
• Monitor ECG in patients with left ventricular
hypertrophy or left ventricular dysfunction
Elderly
• Some patients may tolerate lower doses
better
Children and Adolescents
• Safety and effi cacy 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
• Effective June 30, 2015, the US FDA
requires changes to the content and format
of pregnancy and lactation information
in prescription drug labels, including
the elimination of the pregnancy letter
categories; the Pregnancy and Lactation
Labeling Rule (PLLR or fi nal rule) applies
only to prescription drugs and will be
phased in gradually for drugs approved on
or after June 30, 2001
• Controlled studies have not been
conducted in pregnant women
• Some animal studies have shown adverse
effects
Breast Feeding
• Unknown if dextromethorphan/quinidine
is secreted in human breast milk, but all
THE ART OF PSYCHOPHARMACOLOGY
Potential Advantages
• No other approved agent for PBA
Potential Disadvantages
• CYP450 2D6 poor metabolizers may
require dose reduction
• In patients with past substance abuse,
especially of dextromethorphan, ketamine,
or PCP
Primary Target Symptoms
• Uncontrollable crying
• Uncontrollable laughter
Pearls
• Quinidine is intended to increase the
actions of dextromethorphan by inhibiting
its metabolism by CYP450 2D6; therefore,
poor metabolizers of CYP450 2D6 may not
benefi t as much from this treatment while
still experiencing adverse effects associated
with quinidine
• Affective instability in Alzheimer disease
may be treatable with this agent, including
agitation, allowing antipsychotics to be
avoided in this population
• Some men express emotional lability as
laughter and anger rather than laughter and
crying
• Affective instability in PTSD and in mild
traumatic brain injury may be improved by
dextromethorphan/quinidine
• Similar binding properties to ketamine
suggest possible effi cacy in both
treatment-resistant depression and
chronic pain
