Aggressive outbursts and emotional lability in a 16-year-old boy
Mr. X, age 16, is having increasingly frequent aggressive outbursts that are almost always preceded by inappropriate laughing or crying. How would you help him?
The authors’ observations
Decreasing the severity and frequency of episodes constitutes the mainstay of treating PBA. In the past, off-label treatments, including selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants, were prescribed to reduce PBA symptoms.5 Currently, dextromethorphan/quinidine is the only FDA-approved medication for treating PBA; however, its use in patients younger than age 18 is considered investigational.
Atypical antipsychotics, such as olanzapine and risperidone, have more warnings and precautions than dextromethorphan/quinidine. Risperidone has a “black-box” warning for QT prolongation, in addition to death and stroke in elderly patients.10 Although dextromethorphan/quinidine does not have a black-box warning, it does increase the risk of QT prolongation, and patients with cardiac risk factors should undergo an electrocardiogram before starting this medication. Additionally, risperidone and olanzapine are known to cause significant weight gain, which can increase the risk of developing hyperlipidemia, metabolic syndrome, and type 2 diabetes mellitus.10,11 Neuroleptic malignant syndrome (NMS) is a potentially life-threatening adverse effect of all antipsychotics. NMS is characterized by fever, rigidity, altered consciousness, and increased heart and respiratory rates.12
Quinidine increases the bioavailability of dextromethorphan by inhibiting CYP2D6. When dextromethorphan/quinidine is simultaneously used with an SSRI that also inhibits CYP2D6, such as paroxetine or fluoxetine, the patient may be at increased risk for developing adverse effects such as respiratory depression and serotonin syndrome.13
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