Psychopharmacology and Toxicology
Emily Smith, MD
Resident Physician
ChristianaCare
Newark, Delaware
Kathryn Shirley, DO (she/her/hers)
Resident Physician
Christiana Care
Newark, Delaware
Avni Shah, DO
Resident
Christiana Care
Newark, Delaware
Robert F. Bahnsen, Jr., MD
Medical Director
ChristianaCare
Wilmington, Delaware
Background:
Dextromethorphan/quinidine (DM/Q; brand name Nuedexta) is a treatment for pseudobulbar affect (PBA) and is also being studied as a potential treatment of agitation, impulsivity, and mood lability in other neurological conditions, including traumatic brain injury (TBI). Here we present 2 cases in which DM/Q was used to treat TBI-related agitation and additional neuropsychiatric symptoms throughout their medical hospitalizations, as prescribed by the psychiatry consult-liaison team.
Case 1:
A 34-year-old male with a history of depression, anxiety, opioid use disorder (OUD), and alcohol use disorder (AUD) presented to the hospital for treatment of numerous injuries sustained in a MVC rollover, including TBI. Psychiatry was consulted on Day 21 to manage persistent agitation, which did not significantly decrease after trials of quetiapine, divalproex sodium, olanzapine, chlorpromazine, lorazepam, clonidine, gabapentin, propranolol, sertraline, and buspirone. Dextromethorphan 20mg/quinidine 10mg was started on hospital day 45. Agitation and impulsivity significantly decreased soon after initiation. Restlessness worsened after DM/Q was discontinued on hospital day 88, and the patient improved again when the medication was restarted on hospital day 94.
Case 2:
A 34-year-old male with a history of OUD in remission, bipolar disorder, and attention-deficit disorder presented to the hospital after being thrown from an ATV. Injuries included bilateral subdural hematoma with right shift and uncal herniation. Psychiatry was consulted to manage persistent agitation, which remained a problem despite treatment with quetiapine, carbamazepine, valproic acid, risperidone, olanzapine, chlorpromazine, propranolol, and gabapentin. DM/Q was started on hospital day 150. Unfortunately, the patient has remained intermittently agitated and aggressive.
Discussion:
Dextromethorphan is a low affinity NMDA receptor antagonist, high-affinity sigma-1 antagonist, and serotonin and norepinephrine reuptake inhibitor. Quinidine is a CYP450 2D6 inhibitor that increases the bioavailability of dextromethorphan (Taylor, 2016). In addition to treating emotional lability in PBA, there has been some evidence to suggest DM/Q may be an effective treatment for symptoms in other neurological conditions, such as TBI-related agitation and irritability (Alexandroni, 2013; Garcia-Baran, 2016). As seen in the cases above, the effectiveness of DM/Q in cases of TBI-related agitation is variable.
Conclusion:
Dextromethorphan/quinidine may be an effective treatment for TBI-related behaviors and agitation. Further research is warranted.
References:
1. Alexandroni, A., Dennison, A. C., & White, P. K. (2013). Dextromethorphan/quinidine for the management of agitation in a traumatic brain injured patient: A case report. PM&R, 5(9S). https://doi.org/10.1016/j.pmrj.2013.08.463
2. Garcia-Baran, D., Johnson, T. M., Wagner, J., Shen, J., & Geers, M. (2016). Therapeutic Approach of a High Functioning Individual With Traumatic Brain Injury and Subsequent Emotional Volatility With Features of Pathological Laughter and Crying With Dextromethorphan/Quinidine. Medicine, 95(12), e2886. https://doi.org/10.1097/MD.0000000000002886
3.Taylor, C. P., Traynelis, S. F., Siffert, J., Pope, L. E., & Matsumoto, R. R. (2016). Pharmacology of dextromethorphan: Relevance to dextromethorphan/quinidine (Nuedexta®) clinical use. Pharmacology & Therapeutics, 164, 170–182. https://doi.org/10.1016/j.pharmthera.2016.04.010
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