Drug Efficacy in the Treatment of Antipsychotic-Induced Akathisia: A Systematic Review and Network Meta-Analysis.

Importance: Antipsychotic-induced akathisia (AIA) occurs in 14% to 35% of patients treated with antipsychotics and is associated with increased suicide and decreased adherence in patients with schizophrenia. However, no comprehensive review and network meta-analysis has been conducted to compare the efficacy of treatments for AIA. Objective: To compare the efficacy associated with AIA treatments. Data Sources: Three databases (MEDLINE, Web of Science, and Google Scholar) were systematically searched by multiple researchers for double-blind randomized clinical trials (RCTs) comparing active drugs for the treatment of AIA with placebo or another treatment between May 30 and June 18, 2023. Study Selection: Selected studies were RCTs that compared adjunctive drugs for AIA vs placebo or adjunctive treatment in patients treated with antipsychotics fulfilling the criteria for akathisia, RCTs with sample size of 10 patients or more, only trials in which no additional drugs were administered during the study, and RCTs that used a validated akathisia score. Trials with missing data for the main outcome (akathisia score at the end points) were excluded. Data Extraction and Synthesis: Data extraction and synthesis were performed, estimating standardized mean differences (SMDs) through pairwise and network meta-analysis with a random-effects model. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed. Main Outcomes and Measures: The primary outcome was the severity of akathisia measured by a validated scale at the last available end point. Results: Fifteen trials involving 492 participants compared 10 treatments with placebo. Mirtazapine (15 mg/d for ≥5 days; SMD, -1.20; 95% CI, -1.83 to -0.58), biperiden (6 mg/d for ≥14 days; SMD, -1.01; 95% CI, -1.69 to -0.34), vitamin B6 (600-1200 mg/d for ≥5 days; SMD, -0.92; 95% CI, -1.57 to -0.26), trazodone (50 mg/d for ≥5 days; SMD, -0.84; 95% CI, -1.54 to -0.14), mianserin (15 mg/d for ≥5 days; SMD, -0.81; 95% CI, -1.44 to -0.19), and propranolol (20 mg/d for ≥6 days; SMD, -0.78; 95% CI, -1.35 to -0.22) were associated with greater efficacy than placebo, with low to moderate heterogeneity (I2 = 34.6%; 95% CI, 0.0%-71.1%). Cyproheptadine, clonazepam, zolmitriptan, and valproate did not yield significant effects. Eight trials were rated as having low risk of bias; 2, moderate risk; and 5, high risk. Sensitivity analyses generally confirmed the results for all drugs except for cyproheptadine and propranolol. No association between effect sizes and psychotic severity was found. Conclusions and Relevance: In this systematic review and network meta-analysis, mirtazapine, biperiden, and vitamin B6 were associated with the greatest efficacy for AIA, with vitamin B6 having the best efficacy and tolerance profile. Trazodone, mianserin, and propranolol appeared as effective alternatives with slightly less favorable efficacy and tolerance profiles. These findings should assist prescribers in selecting an appropriate medication for treating AIA.

Acetaminophen improves tardive akathisia induced by dopamine D2 receptor antagonists.

Tardive akathisia is a movement disorder characterized by internal restlessness with an uncontrollable urge to move, leading to repetitive movements. It is a common side effect of long-term treatment with dopamine D2 receptor antagonists. In the present study, we analyzed the FDA Adverse Event Reporting System and IBM MarketScan Research Database to find a drug that can be used concomitantly with dopamine D2 receptor antagonists and still reduce the risk of akathisia. Acetaminophen was determined to be the most effective akathisia-suppressing drug. In an experimental validation of the hypothesis, chronic treatment of rats with haloperidol caused akathisia symptoms, including increased stereotyped behavior and locomotor activity, and decreased immobility time. Acute treatment with acetaminophen significantly attenuated haloperidol-induced akathisia. In the ventral striata of these rats, acetaminophen prevented haloperidol-induced decrease in the number of c-Fos+ preproenkephalin+ neurons. These results suggest that acetaminophen is effective in suppressing tardive akathisia by activating indirect-pathway medium spiny neurons.

Akathisia Among Patients Undergoing Antipsychotic Therapy: Prevalence, Associated Factors, and Psychiatric Impact.

OBJECTIVES: The prevalence of akathisia is variably reported in the literature and its psychiatric impact is little studied. The aim of this study was to establish the prevalence, the associated factors, and the psychiatric impact of akathisia among patients undergoing antipsychotic treatment. METHODS: A cross-sectional descriptive study was carried out at the Department of Psychiatry A, at Razi Hospital, in Tunis. It included patients with psychosis, undergoing antipsychotic treatment, from June 2016 to February 2017. Akathisia was diagnosed according to the Barnes Akathisia Scale. RESULTS: The prevalence of akathisia was 19.5% (n = 24, schizophrenia/schizoaffective disorder, n = 20; bipolar disorder, n = 4). The delay between the diagnosis of the disease and the onset of akathisia was 7.1 ± 8.8 years. Among the sample of patients with akathisia, 20/24 were on monotherapy of which 14 on conventional antipsychotics and six on atypical antipsychotics. Patients with akathisia were on atypical (8/24), low-potency conventional (4/24), or high-potency conventional (17/24) antipsychotics. The average dose of antipsychotics in chlorpromazine equivalent was 2294.5 ± 3037.7 mg. After adjusting for confounders, the only factor significantly positively associated with the diagnosis of akathisia was the dose of antipsychotics prescribed ( P = 0.01). The following psychiatric manifestations were reported by patients with akathisia: dysphoria/irritability (16/23), anxiety (18/24), sadness (15/24), suicidal thoughts (11/24), heteroaggressivity (8/23), sleep disturbances (16/24), and suicidal attempts (9/24). CONCLUSIONS: Despite the high psychiatric and social burden of akathisia, it remains largely underdiagnosed and undertreated, because in part of its subjective component.

Effects of the selective dopamine D3 receptor antagonist PG01037 on morphine-induced hyperactivity and antinociception in mice.

Recent preclinical studies have reported that pretreatment with the novel and highly-selective dopamine D3 receptor (D3R) antagonists R-VK4-40 or VK4-116 attenuates the abuse-related behavioral effects of oxycodone while enhancing its analgesic properties. However, whether these observed effects are generalizable to the broad class of D3R antagonists and/or extend to opioids other than oxycodone has not been extensively explored. The present study sought to assess the impact of pretreatment with another selective D3R antagonist, PG01037, on several behavioral effects of morphine in mice. C57Bl/6 J mice were pretreated with PG01037 (0-10 mg/kg) and tested for 1) hyperlocomotion induced by acute morphine (5.6-56 mg/kg), 2) locomotor sensitization following repeated morphine (56 mg/kg), 3) antinociception following acute morphine (18 mg/kg), and 4) catalepsy following administration of PG01037 alone or in combination with morphine (56 mg/kg). PG01037 dose-dependently attenuated morphine-induced hyperlocomotion and morphine-induced antinociception at doses that did not alter basal locomotion or nociception alone, but did not prevent the induction of locomotor sensitization following repeated morphine administration. Moreover, PG01037 did not induce catalepsy either alone or in combination with morphine. These results suggest that attenuation of acute opioid-induced hyperactivity may be a behavioral effect shared among D3R-selective antagonists, thus supporting continued investigations into their use as potential treatments for opioid use disorder. However, PG01037 is unlike newer, highly-selective D3R antagonists in its capacity to reduce opioid-induced antinociception, indicating that modulation of opioid analgesia may vary across different D3R antagonists.

Struggling to find Effective Pharmacologic Options for Akathisia? B-CALM!

Akathisia is a movement disorder affecting the trunk and limbs, characterized by subjective and objective restlessness. Key signs include continual, repetitive rocking, leg shuffling, and fidgeting. Antipsychotic-induced akathisia is optimally managed by reducing the medication dose or switching to a second generation antipsychotic that is less prone to inducing akathisia. However, since medication changes are often not feasible, we review the available classes of rescue agents for akathisia symptoms. The fitting acronym, "B-CALM", which stands for Beta-blockers, Clonazepam, Anticholinergics, cLonidine and Mirtazapine, will assist prescribers in facile recall of evidence-based treatment options for akathisia. Pharmacological agents such as mianserin, trazodone, Vit B6, amantadine, gabapentin, and pregabalin have also been examined as treatment options for antipsychotic-induced akathisia. Although initial exploratory reports on these agents have been promising, the current evidence is insufficient. Akathisia has a good prognosis when managed early in the course of treatment. A variety of safe rescue agents are available for the management of this condition, however, current evidence best supports the use of propranolol and mirtazapine.

A randomized trial comparing physostigmine vs lorazepam for treatment of antimuscarinic (anticholinergic) toxidrome.

BACKGROUND: Toxicity from antimuscarinic agents precipitates a constellation of signs and symptoms; two of the most significant are agitation and delirium. Benzodiazepines are commonly used for treatment; physostigmine is also effective but is underutilized due to concerns for safety and short duration of action. The objective of this study was to compare lorazepam to physostigmine for the treatment of antimuscarinic delirium and agitation. METHODS: This was a blinded, randomized clinical trial in patients presenting for antimuscarinic toxidrome. Inclusion criteria were: ≥10-<18 years old, at least one central and two peripheral antimuscarinic symptoms, delirium and moderate agitation. Subjects were randomized to either (1) lorazepam bolus (0.05 mg/kg) followed by a 4-h normal saline infusion, or (2) physostigmine 0.02 mg/kg bolus followed by a 4-h physostigmine infusion (0.02 mg/kg/h). Primary outcomes were the control of delirium and agitation after bolus and during the infusion. RESULTS: Ten (53%) subjects were enrolled in the lorazepam arm, 9 (47%) in the physostigmine arm. Diphenhydramine was the most common agent ingested (16, 84%). Fewer patients receiving physostigmine had delirium after the initial bolus (44% vs 100%, p = 0.01) and at the 4th hour of infusion (22% vs 100%, p < 0.001) compared to patients who received lorazepam. There was a significant decrease in agitation scores in the physostigmine arm compared to the lorazepam arm after the initial bolus (89% vs 30%, p = 0.02), but no difference at the 4th hour of infusion (p > 0.99). There were no seizures, bradycardia, bronchorrhea, bronchospasm, intubation, or cardiac dysrhythmias. CONCLUSION: Physostigmine was superior to lorazepam in controlling antimuscarinic delirium and agitation after bolus dosing, and control of delirium after a 4-h infusion. There were no serious adverse events in either treatment arm. Physostigmine bolus and infusion should be considered in adolescent patients with significant delirium and agitation from antimuscarinic agents.

Trazodone as an Alternative Treatment for Neuroleptic-Associated Akathisia: A Placebo-Controlled, Double-Blind, Clinical Trial.

BACKGROUND: Akathisia is a distressing extrapyramidal complication that follows the use of antipsychotic medications. Early treatment of neuroleptic-associated akathisia (NAA) is of great importance because it may lead to poor therapeutic response and ultimately treatment noncompliance. Considering the lack of adequate response of some patients to conventional treatments and the assumption that serotonin might be involved in the pathophysiology of the disease in addition to dopaminergic mechanisms, we aimed to evaluate the effectiveness of trazodone as an antidepressant agent with strong antagonistic effects on serotonin receptors in the treatment of akathisia. METHODS: In a double-blind clinical trial, 52 patients receiving antipsychotic medications who were diagnosed to have mild to severe NAA using Barnes Akathisia Rating Scale were treated with trazodone 50 mg daily for 5 days and compared with the placebo control group. RESULTS: Patients receiving trazodone did not show a significant difference compared with the control group in terms of the severity of akathisia symptoms until the third day of the study. In contrast, at the end of the fifth day, there was a significant improvement in objective (P = 0.01) and subjective (P = 0.001) symptoms of akathisia and the global clinical assessment of akathisia scale (P = 0.001). Moreover, there was no clear difference between trazodone and placebo group in terms of adverse effects. CONCLUSIONS: Considering the antagonistic effect of trazodone on postsynaptic 5-hydroxytryptamine2A receptors as a possible mechanism of efficacy of this agent in the treatment of NAA, this study suggests that trazodone might be an effective and relatively safe drug.

Intravenous Migraine Treatment in Children and Adolescents.

PURPOSE OF REVIEW: Pediatric migraine is a common, chronic, and disabling neurological disorder in children and adolescents. Outpatient management is not always effective, and intravenous migraine management may be necessary for headache treatment in the pediatric emergency department. Most current treatment is based on retrospective evidence and there is a lack of well-designed randomized double-blinded controlled pediatric studies. Intravenous drug treatment agents including intravenous fluids, prochlorperazine, diphenhydramine, metoclopramide, dexamethasone, magnesium, valproate and propofol, and dihydroergotamine are reviewed in this paper. RECENT FINDINGS: Nineteen studies were reviewed including one prospective randomized double-blind; one single-blinded randomized; one prospective; and one open-label, randomized clinical trial. Most studies were retrospective and the quality of the studies was limited. No definite conclusions can be drawn from the studies, but appropriate prospective trials between major pediatric headache institutions will move pediatric intravenous migraine management forward.

Treatment of Antipsychotic-Induced Akathisia: Role of Serotonin 5-HT2a Receptor Antagonists.

Akathisia is one of the most prevalent and distressing adverse effects associated with antipsychotic drug treatment. Propranolol, a non-selective beta-adrenergic receptor antagonist, is currently considered a first-line treatment for antipsychotic-induced akathisia (AIA). Surprisingly, the evidence for its anti-akathisia effect is modest. Propranolol's side effects (e.g. orthostatic hypotension, bradycardia), contraindications (e.g. asthma) and increased complexity in titration schedules limit its use in some patients. Anticholinergic agents and benzodiazepines merely provide symptomatic relief in patients with AIA. Effective and well-tolerated treatment remains a major unmet need in akathisia and warrants a search for new anti-akathisia agents. Accumulating evidence during the last two decades indicates that agents with marked postsynaptic serotonin 5-HT2a receptor antagonism (ritanserin, cyproheptadine, trazodone, mianserin, mirtazapine) may represent a new class of potential anti-akathisia remedies. Among these agents, low-dose mirtazapine (7.5 mg or 15 mg once daily) has demonstrated the most compelling evidence for therapeutic efficacy. In this narrative review we highlight the clinical significance of AIA, outline major approaches for its management and propose a practical algorithm for its treatment.

Analytically Confirmed Intoxication by 4-Fluoromethylphenidate, an Analog of Methylphenidate.

4-Fluoromethylphenidate (4F-MPH) is an halogenated derivative of methylphenidate (MPH), a re-uptake inhibitor for dopamine and norepinephrine used for the treatment of attention deficit hyperactivity disorders. In the last few years, several compounds structurally related to MPH have been marked as new psychoactive substances (NPS) with stimulating and euphoric effects similar to the parent drug, but with more dopaminergic activity. This report represents the first case of an analytically confirmed non-fatal intoxication by 4F-MPH. A 26-year-old female was admitted to the emergency department with neuropsychiatric and cardiologic symptoms that lasted for a week, during which she sniffed a powder named 4F-MPH acquired as entactogen on the Internet. The patient required sedation with intravenous diazepam and was discharged two days later with a prescription of promazine and quetiapine. The seized product was analytically characterized by gas chromatography-mass spectrometry, liquid chromatography high-resolution mass spectrometry and nuclear magnetic resonance. These analyses confirmed the composition of the product as a 4F-MPH diastereomeric (±)-threo and (±)-erythro mixture, with a large preponderance of the active (±)-threo isomer. A minimal validation, intended for rare analytes, was performed for the quantification of 4F-MPH in the biological samples by liquid chromatography-tandem mass spectrometry. Accuracy (bias) and precision were within ±15% for both blood and urine. The blood and urine concentration of (±)-threo 4F-MPH were 32 ng/mL and 827 ng/mL, respectively. Analyses for classic drugs (opiates, methadone, cocaine, cannabis metabolites, amphetamines, ecstasy and LSD), ethanol, qualitative full screen by gas chromatography-mass spectrometry and targeted analysis for 50 NPS by liquid chromatography-tandem mass spectrometry tested negative; comorbidities were excluded, too. Based on these data, it can be assumed that the clinical manifestations were due to 4F-MPH only.

Long-term safety and tolerability of cariprazine as adjunctive therapy in major depressive disorder.

Lack of treatment response is a critical problem in major depressive disorder (MDD). Cariprazine is a D3-preferring dopamine D3/D2 receptor partial agonist and 5-HT1A partial agonist. This phase 3, multicenter, open-label, long-term (26-week), flexible-dose (1.5-4.5 mg/day) study assessed the long-term safety and tolerability of cariprazine used adjunctively with antidepressant therapy in adult patients with MDD who had either completed a lead-in study (n=311) or had been newly recruited (n=131). A higher percentage of continuing patients (66.2%) than new patients (35.9%) completed the study. The most common reason for discontinuation was adverse events (AEs; 13.9%); 79% of patients experienced a treatment-emergent AE [most common: akathisia (15.9%,) headache (11.6%)]. Serious AEs occurred in 2% of patients; two deaths occurred (one traffic accident, one completed suicide, both considered unrelated to treatment). The mean changes in clinical laboratory, cardiovascular, and ophthalmologic parameters were generally not clinically relevant. The mean (SD) changes from the open-label baseline in Montgomery-Åsberg Depression Rating Scale total score and Clinical Global Impression-Severity score at week 26 were -7.3 (9.5) and -1.0 (1.2), respectively. By week 26, 53.3% of patients were in remission (Montgomery-Åsberg Depression Rating Scale total score≤10). The results suggest that cariprazine was generally safe and well tolerated as adjunctive therapy to treat MDD.

Very Low-Dose Mirtazapine (7.5 mg) in Treatment of Acute Antipsychotic-Associated Akathisia.

BACKGROUND: Some evidence suggests that off-label use of mirtazapine (15 mg) is effective in treatment of acute antipsychotic-associated akathisia (AAA). We analyzed whether a lower dose of mirtazapine (7.5 mg) maintained its antiakathisia properties while exhibiting better tolerability in patients with schizophrenia and mood disorders who developed acute AAA. METHODS: Medical charts were retrospectively evaluated for 12 patients with AAA. All scored at least 2 (mild akathisia) on the Barnes Akathisia Rating Scale (BARS) and were treated with mirtazapine (7.5 mg) for a mean of 10.3 days. RESULTS: There was a statistically significant decrease in the BARS subjective, distress, and global (P < 0.01 to P < 0.001), but not objective (P = 0.63), subscales. Five participants (41.6%) fulfilled the predefined criterion of response, a decrease of at least 2 points on the BARS global subscale. The positive antiakathisia effect of mirtazapine was observed predominantly in aripiprazole-treated patients. Mirtazapine (7.5 mg) was well tolerated, and no clinically significant adverse effects, primarily drowsiness or increased appetite, were reported. CONCLUSIONS: A large-scale controlled evaluation is warranted to substantiate clinical utility of off-label use of mirtazapine (7.5 mg) for patients with AAA.

Combined treatment with a selective PDE10A inhibitor TAK-063 and either haloperidol or olanzapine at subeffective doses produces potent antipsychotic-like effects without affecting plasma prolactin levels and cataleptic responses in rodents.

Activation of indirect pathway medium spiny neurons (MSNs) via promotion of cAMP production is the principal mechanism of action of current antipsychotics with dopamine D2 receptor antagonism. TAK-063 [1-[2-fluoro-4-(1H-pyrazol-1-yl)phenyl]-5-methoxy-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one] is a novel phosphodiesterase 10A inhibitor that activates both direct and indirect pathway MSNs through increasing both cAMP and cGMP levels by inhibition of their degradation. The activation of indirect pathway MSNs through the distinct mechanism of action of these drugs raises the possibility of augmented pharmacological effects by combination therapy. In this study, we evaluated the potential of combination therapy with TAK-063 and current antipsychotics, such as haloperidol or olanzapine after oral administration. Combined treatment with TAK-063 and either haloperidol or olanzapine produced a significant increase in phosphorylation of glutamate receptor subunit 1 in the rat striatum. An electrophysiological study using rat corticostriatal slices showed that TAK-063 enhanced N-methyl-D -aspartic acid receptor-mediated synaptic responses in both direct and indirect pathway MSNs to a similar extent. Further evaluation using pathway-specific markers revealed that coadministration of TAK-063 with haloperidol or olanzapine additively activated the indirect pathway, but not the direct pathway. Combined treatment with TAK-063 and either haloperidol or olanzapine at subeffective doses produced significant effects on methamphetamine- or MK-801-induced hyperactivity in rats and MK-801-induced deficits in prepulse inhibition in mice. TAK-063 at 0.1 mg/kg did not affect plasma prolactin levels and cataleptic response from antipsychotics in rats. Thus, TAK-063 may produce augmented antipsychotic-like activities in combination with antipsychotics without effects on plasma prolactin levels and cataleptic responses in rodents.

Antimanic Efficacy of a Novel Kv3 Potassium Channel Modulator.

Kv3.1 and Kv3.2 voltage-gated potassium channels are expressed on parvalbumin-positive GABAergic interneurons in corticolimbic brain regions and contribute to high-frequency neural firing. The channels are also expressed on GABAergic neurons of the basal ganglia, substantia nigra, and ventral tegmental area (VTA) where they regulate firing patterns critical for movement control, reward, and motivation. Modulation of Kv3.1 and Kv3.2 channels may therefore have potential in the treatment of disorders in which these systems have been implicated, such as bipolar disorder. Following the recent development of a potassium channel modulator, AUT1-an imidazolidinedione compound that specifically increases currents mediated by Kv3.1 and Kv3.2 channels in recombinant systems-we report that the compound is able to reverse 'manic-like' behavior in two mouse models: amphetamine-induced hyperactivity and ClockΔ19 mutants. AUT1 completely prevented amphetamine-induced hyperactivity in a dose-dependent manner, similar to the atypical antipsychotic, clozapine. Similar efficacy was observed in Kv3.2 knockout mice. In contrast, AUT1 was unable to prevent amphetamine-induced hyperactivity in mice lacking Kv3.1 channels. Notably, Kv3.1-null mice displayed baseline hyperlocomotion, reduced anxiety-like behavior, and antidepressant-like behavior. In ClockΔ19 mice, AUT1 reversed hyperactivity. Furthermore, AUT1 application modulated firing frequency and action potential properties of ClockΔ19 VTA dopamine neurons potentially through network effects. Kv3.1 protein levels in the VTA of ClockΔ19 and WT mice were unaltered by acute AUT1 treatment. Taken together, these results suggest that the modulation of Kv3.1 channels may provide a novel approach to the treatment of bipolar mania.

Incidence of antiemetic-induced akathisia in patients at a comprehensive cancer center.

INTRODUCTION: Akathisia is a common and severely disabling medication-induced movement disorder. The condition is often missed, and patients suffer for a long time until diagnosed and managed properly. It is important to bring awareness to the clinicians for early detection and management of akathisia. METHODS: We reviewed a 4-year record of patients seen at a comprehensive cancer center for anxiety and restlessness. Patients diagnosed with akathisia and the medications causing akathisia were identified. Management of akathisia is discussed. RESULTS: The results showed that 4.7% of patients developed akathisia while taking antiemetic agents to control chemotherapy-induced nausea/vomiting. Early detection and management of akathisia resulted in quick recovery and reduced patients' suffering. CONCLUSION: Akathisia is an unpleasant feeling of motor restlessness with anxiety. Clinicians need to have a full understanding to identify the subtle difference between functional anxiety and akathisia.

[Drug-Induced Akathisia].

Akathisia consists of subjective inner restlessness, such as awareness of the inability to remain seated, restless legs, fidgetiness, and the desire to move constantly, and of objective increased motor phenomena, such as body rocking, shifting from foot to foot, stamping in place, crossing and uncrossing legs, pacing around. Although the broad definition of akathisia includes the inner and motor restlessness observed in patients with idiopathic Parkinson's disease, post-encephalitic parkinsonism, and restless legs syndrome, here we exclusively focus on the narrow definition of antipsychotic-induced akathisia. The most reliable treatment for acute akathisia is the reduction or the withdrawal of antipsychotic medication. However, this is often not possible because it may worsen the patients' mental condition. Various pharmacological agents have been used for the treatment of this condition. These include anticholinergic agents (e.g., biperiden and trihexyphenidyl), benzodiazepines, beta-adrenoceptor blockers (e.g., propranolol), and serotonin 2A receptor antagonists (e.g., mianserin, cyproheptadine, and mirtazapine).

Effect of Amantadine on Agitation in Critically Ill Patients With Traumatic Brain Injury.

OBJECTIVE: This study aimed to compare the presence of agitation in traumatic brain injury patients treated with amantadine with those not treated with amantadine in the intensive care unit (ICU). METHODS: This was a retrospective cohort study conduced in a trauma ICU of a tertiary care institution in the United States. Patients who received amantadine were compared with patients who did not receive amantadine. The primary outcome measure was the presence of agitation, defined as the Richmond Agitation Sedation Scale score of +2 or higher. Secondary comparisons included haloperidol use, benzodiazepine use, opioid use, and ICU length of stay. RESULTS: A total of 139 patients were included in the study cohort (70 patients in the amantadine group, 69 patients in the no-amantadine group). There were more patients who had agitation in the amantadine group (38% vs 14%, P = 0.018). Patients who received amantadine received more opioids in fentanyl equivalents (10.3 [interquartile range {IQR}, 6.3-20.4] µg/kg vs 7.4 [IQR, 2.1-12.6] µg/kg, P = 0.009) and had a longer ICU length of stay (4.5 [IQR, 3-10] days vs 3 [IQR, 2-5] days, P = 0.010). Haloperidol use and benzodiazepine use were similar between groups. CONCLUSIONS: The early use of amantadine after traumatic brain injury may increase the risk of agitation. This could increase opioid consumption and ICU length of stay.