Efficacy of Dextromethorphan/Quinidine for Patients With Psychosis-Related Aggression: A Retrospective Case Series

Background Treatment-resistant aggressive behavior is a complex psychoneurological phenomenon with high health care and societal costs commonly observed in mental illnesses involving psychosis. Here, we report a preliminary evaluation of treatment with dextromethorphan/quinidine in 4 adult patients with significant history of psychosis-related aggression and impulsive behaviors. Methods The files of 4 inpatients with DSM-5-defined psychotic disorder and treatment-resistant aggression treated at the Oregon State Hospital (Salem, Oregon) between June and November of 2017 were retrospectively analyzed. The patients (age: mean ± SD = 59.8 ± 7.6) received open-label treatment with dextromethorphan/quinidine (final dose 20 mg/10 mg twice daily) for at least 12 weeks. Outcome was measured on the basis of patient self-report, treatment team evaluation, and physical examination by psychiatrists and primary care physicians. Results Three of the 4 patients were considered responders to dextromethorphan/quinidine based on clinical impressions of reduction in aggression and impulsive behavior. The nonresponder, who had a history of multiple traumatic brain injuries, showed mild improvement in agitation but continued to display impulsive self-harm behavior despite treatment. Dextromethorphan/quinidine was generally well-tolerated. No metabolic, gastrointestinal, or cardiovascular side effects were observed. Conclusions These preliminary findings support dextromethorphan/quinidine as a potential alternative to conventional regimens for treating aggression and impulsive behavior in patients with psychotic disorder. These results should be interpreted cautiously, as extended, double-blinded, placebo-controlled studies with a larger sample size are needed to validate findings from this retrospective case series.