Influence of a single oral dose of trazodone on intradermal histamine reactivity in clinically healthy dogs.

BACKGROUND: Drug interactions are significant considerations for intradermal testing (IDT). Trazodone (TRZ) is an anxiolytic and selective histaminergic (H1 ) antagonist with no interaction in human prick tests; however, interaction in canine IDT is unknown. HYPOTHESIS/OBJECTIVES: Trazodone will not adversely affect intradermal histamine reactions in dogs. ANIMALS: Fourteen nonanxious, nonatopic, healthy client-owned dogs were enrolled in this randomised, blinded, cross-over study. MATERIALS AND METHODS: Dogs were randomised to receive low-dose TRZ (4 mg/kg) (Teva Pharmaceuticals), high-dose TRZ (8 mg/kg) or no TRZ per os two hours before intravenous sedation with dexmedetomidine (5 mcg/kg) (Dexdomitor; Zoetis). Intradermal testing was performed with five quadrupling dilutions of histamine (1:100,000 to 1:25,600,000 w/v; Greer) and 0.9% saline (Hospira), observing a minimum two weeks washout period between treatments. Two observers, who were blinded to treatment and the identity of the injections, evaluated each test using previously established subjective and objective methods. RESULTS: The mean wheal diameter of histamine 1:1,600,000 w/v was significantly smaller with low-dose TRZ (4 mg/kg) compared to the control group (p = 0.048; repeated measures ANOVA with post hoc Tukey's test). For all other histamine dilutions and saline, mean wheal diameter was not significantly different among groups. There were no significant differences in the subjective scores of all histamine dilutions and saline (p > 0.05; Friedman test). CONCLUSION AND CLINICAL RELEVANCE: A single oral dose of TRZ does not adversely affect intradermal histamine reactions in dogs.

The impact of single-dose trazodone administration on plasma endogenous adrenocorticotropic hormone and serum cortisol concentrations in healthy dogs.

BACKGROUND: Conditions affecting the hypothalamic-pituitary-adrenal (HPA) axis are common in dogs. Testing the function of the HPA axis includes measurement of endogenous adrenocorticotropic hormone (eACTH) and performance of an adrenocorticotropic hormone (ACTH) stimulation test. Trazodone is commonly administered to dogs to decrease stress. In humans, trazodone significantly decreases plasma cortisol concentration via alpha-1 adrenergic activity. OBJECTIVES: Determine the influence of trazodone on eACTH and serum cortisol concentrations in healthy dogs. ANIMALS: Fourteen healthy, adult, companion dogs. METHODS: Prospective, randomized placebo-controlled study. Trazodone (8-10 mg/kg) or placebo was administered PO 1 hour before eACTH measurement and ACTH stimulation testing. After a ≥7-day wash-out period, dogs received the opposite treatment. Differences in eACTH, pre- and post-ACTH stimulation cortisol concentrations, and delta (difference between pre- and post-ACTH) cortisol concentrations were analyzed using a paired t or signed-rank test with a P < .05 significance level. RESULTS: The eACTH concentrations were not significantly different (P = .23) between treatments. Similarly, no significant differences were found in the pre-ACTH cortisol concentrations between treatments (P = .40). Post-ACTH cortisol concentrations (P = .05) and delta cortisol concentrations (P = .04) were significantly lower when the dogs were treated with trazodone. CONCLUSIONS: Preliminary data suggest trazodone administration dampens the adrenocortical response to stimulation in healthy dogs. If similar effects are found in dogs with adrenal disease, the use of trazodone may affect diagnosis and clinical decision making in these populations.

Effects of trazodone and dexmedetomidine on fentanyl-mediated reduction of isoflurane minimum alveolar concentration in cats.

OBJECTIVE: To screen modulators of biogenic amine (BA) neurotransmission for the ability to cause fentanyl to decrease isoflurane minimum alveolar concentration (MAC) in cats, and to test whether fentanyl plus a combination of modulators decreases isoflurane MAC more than fentanyl alone. STUDY DESIGN: Prospective, experimental study. ANIMALS: A total of six adult male Domestic Short Hair cats. METHODS: Each cat was anesthetized in three phases with a 1 week washout between studies. In phase 1, anesthesia was induced and maintained with isoflurane, and MAC was measured in duplicate using a tail clamp stimulus and standard bracketing technique. A 21 ng mL-1 fentanyl target-controlled infusion was then administered and MAC measured again. In phase 2, a single cat was administered a single BA modulator (buspirone, haloperidol, dexmedetomidine, pregabalin, ramelteon or trazodone) in a pilot drug screen, and isoflurane MAC was measured before and after fentanyl administration. In phase 3, isoflurane MAC was measured before and after fentanyl administration in cats co-administered trazodone and dexmedetomidine, the two BA modulator drugs associated with fentanyl MAC-sparing in the screen. Isoflurane MAC-sparing by fentanyl alone, trazodone-dexmedetomidine and trazodone-dexmedetomidine-fentanyl was evaluated using paired t tests with p < 0.05 denoting significant effects. RESULTS: The MAC of isoflurane was 1.87% ± 0.09 and was not significantly affected by fentanyl administration (p = 0.09). In the BA screen, cats administered trazodone or dexmedetomidine exhibited 26% and 22% fentanyl MAC-sparing, respectively. Trazodone-dexmedetomidine co-administration decreased isoflurane MAC to 1.50% ± 0.14 (p < 0.001), and the addition of fentanyl further decreased MAC to 0.95% ± 0.16 (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl alone does not affect isoflurane MAC in cats, but co-administration of trazodone and dexmedetomidine causes fentanyl to significantly decrease isoflurane requirement.

Trazodone rescues dysregulated synaptic and mitochondrial nascent proteomes in prion neurodegeneration.

The unfolded protein response (UPR) is rapidly gaining momentum as a therapeutic target for protein misfolding neurodegenerative diseases, in which its overactivation results in sustained translational repression leading to synapse loss and neurodegeneration. In mouse models of these disorders, from Alzheimer's to prion disease, modulation of the pathway-including by the licensed drug, trazodone-restores global protein synthesis rates with profound neuroprotective effects. However, the precise nature of the translational impairment, in particular the specific proteins affected in disease, and their response to therapeutic UPR modulation are poorly understood. We used non-canonical amino acid tagging (NCAT) to measure de novo protein synthesis in the brains of prion-diseased mice with and without trazodone treatment, in both whole hippocampus and cell-specifically. During disease the predominant nascent proteome changes occur in synaptic, cytoskeletal and mitochondrial proteins in both hippocampal neurons and astrocytes. Remarkably, trazodone treatment for just 2 weeks largely restored the whole disease nascent proteome in the hippocampus to that of healthy, uninfected mice, predominantly with recovery of proteins involved in synaptic and mitochondrial function. In parallel, trazodone treatment restored the disease-associated decline in synapses and mitochondria and their function to wild-type levels. In conclusion, this study increases our understanding of how translational repression contributes to neurodegeneration through synaptic and mitochondrial toxicity via depletion of key proteins essential for their function. Further, it provides new insights into the neuroprotective mechanisms of trazodone through reversal of this toxicity, relevant for the treatment of neurodegenerative diseases via translational modulation.

Chronic Aripiprazole and Trazodone Polypharmacy Effects on Systemic and Brain Cholesterol Biosynthesis.

The concurrent use of several medications is a common practice in the treatment of complex psychiatric conditions. One such commonly used combination is aripiprazole (ARI), an antipsychotic, and trazodone (TRZ), an antidepressant. In addition to their effects on dopamine and serotonin systems, both of these compounds are inhibitors of the 7-dehydrocholesterol reductase (DHCR7) enzyme. To evaluate the systemic and nervous system distribution of ARI and TRZ and their effects on cholesterol biosynthesis, adult mice were treated with both ARI and TRZ for 21 days. The parent drugs, their metabolites, and sterols were analyzed in the brain and various organs of mice using LC-MS/MS. The analyses revealed that ARI, TRZ, and their metabolites were readily detectable in the brain and organs, leading to changes in the sterol profile. The levels of medications, their metabolites, and sterols differed across tissues with notable sex differences. Female mice showed higher turnover of ARI and more cholesterol clearance in the brain, with several post-lanosterol intermediates significantly altered. In addition to interfering with sterol biosynthesis, ARI and TRZ exposure led to decreased ionized calcium-binding adaptor molecule 1 (IBA1) and increased DHCR7 protein expression in the cortex. Changes in sterol profile have been also identified in the spleen, liver, and serum, underscoring the systemic effect of ARI and TRZ on sterol biosynthesis. Long-term use of concurrent ARI and TRZ warrants further studies to fully evaluate the lasting consequences of altered sterol biosynthesis on the whole body.

Trazodone for sleep disturbance in opioid dependent patients maintained on buprenorphine: A double blind, placebo-controlled trial.

BACKGROUND: Sleep disturbances are seen even in individuals on opioid agonist treatment (OAT). Established pharmacotherapy for sleep disturbances such as benzodiazepines have misuse potential and increased mortality risk in patients with OAT. No study has explored the role of trazodone on sleep disturbance in individuals maintained on buprenorphine. We aimed to assess the efficacy of trazodone in improving sleep disturbance among individuals maintained on buprenorphine. METHODS: The study was a double-blind, placebo-controlled, parallel, randomised trial. Adult males (18-60 years) stabilised on buprenorphine with Pittsburgh Sleep Quality Index (PSQI) score of above five, without other psychiatric comorbidity were randomised to receive either trazodone (50-150mg per day) or placebo. Sleep-50 questionnaire, Epworth Sleepiness Scale (ESS), Brief Pain Inventory (BPI), Clinical Opiate Withdrawal Scale (COWS), Depression, Anxiety and Stress Scale (DASS)-21, Visual Analogue Scale (VAS) for opioid craving, and PSQI were assessed at baseline and at the end of six weeks. RESULTS: Fifty-one patients were allocated to trazodone arm and 49 to placebo arm. Side-effects of trazodone were minimal and well-tolerated with comparable discontiuation rates between both groups. Significantly greater proportion of patients on trazodone (82%, mean dose 101.9 mg) had PSQI scores five or less than those on placebo (16%) at the end of six weeks. Sleep improvement was in various components like sleep quality, latency, efficiency, and duration of sleep. CONCLUSION: Trazodone is well-tolerated and effective in improving sleep disturbances in individuals with opioid dependence maintained on buprenorphine over a six-week period.

[Treatment of mental disorders caused or triggered by somatic and neurological diseases with the use of the multimodal antidepressant trazodone]. / Terapiya psikhicheskikh rasstroistv, obuslovlennykh libo provotsirovannykh somaticheskoi i nevrologicheskoi patologiei, s primeneniem mul'timodal'nogo antidepressanta trazodon.

The purpose of this narrative review is to relate current data on the molecular mechanisms of action of trazodone with its clinical effects and applicability in mental disorders caused or triggered by somatic and neurological disease, according to available publications. In the article, the prospects for the use of the multimodal antidepressant trazodone are discussed in accordance with therapeutic targets. The latter are discussed in accordance with the typology of the mentioned above psychosomatic disorders. Trazodone is an antidepressant acting primarily due to the blockade of postsynaptic serotonin 5H2A- and 5H2C-receptors, as well as the blockade of serotonin reuptake, but also has affinity for a number of additional receptors. The drug has a favorable safety profile and a wide range of beneficial effects: antidepressive, somnolent, anxiolytic, anti-dysphoric and somatotropic. This makes it possible to influence a wide range of therapeutic targets in the structure of mental disorders caused or triggered by somatic and neurological diseases, carrying out safe and effective psychopharmacotherapy.

Update on Pharmacological Treatment for Comorbid Major Depressive and Alcohol Use Disorders: The Role of Extended-release Trazodone.

BACKGROUND: Major Depressive Disorder (MDD) and Alcohol Use Disorder (AUD) are major public health concerns because of their high prevalence and clinical and functional severity. MDD and AUD commonly co-occur, but effective therapeutic approaches for comorbidity are still scarce. Available evidence on selective serotonin reuptake inhibitors and tricyclic antidepressants held mixed results, and further pharmacological categories have been less investigated. Trazodone is an approved antidepressant drug for adults and has shown efficacy on symptoms like anxiety and insomnia observed in AUD patients as well. Thus, this study aims to evaluate the effect of extended-release trazodone on clinical and functional features in MDD + AUD subjects. METHODS: One hundred MDD + AUD outpatients were retrospectively evaluated at 1, 3, and 6 months of treatment with extended-release trazodone (150-300 mg/day, flexibly dosed). Improvement in depressive symptoms was the primary outcome measure. Changes in anxiety, sleep, functioning, quality of life, clinical global severity, and alcohol craving were also investigated. RESULTS: Trazodone reduced depressive symptoms (p < 0.001) with 54.5% remission at the endpoint. Similar improvements were observed in all secondary outcomes, including anxiety, sleep alterations, and craving (p < 0.001). Only mild side effects were reported and disappeared over time. CONCLUSION: Extended-release trazodone displayed good antidepressant properties in MDD + AUD patients, ameliorating overall symptomatology, functioning, and quality of life, with a good safety/ tolerability profile. Further, it significantly improved sleep disturbances and craving symptoms, which are associated with drinking relapse and worse outcomes. Therefore, trazodone might represent a promising pharmacological option for MDD + AUD patients.

Biochemical and Biophysical in Vitro Studies and Systematic Literature Review on the Antioxidant and Antiglycation Activities of Trazodone.

BACKGROUND/AIMS: Trazodone is a selective serotonin reuptake inhibitor; however, other mechanisms of the drug's anti-depressive properties have also been postulated. Hence, the aim of the study was to perform a systematic review and assess antiglycoxidative properties of trazodone in in vitro models. METHODS: Trazodone's scavenging and chelating properties were measured with spectrophotometric method. The impact of the drug on carbonyl/oxidative stress was marked in the bovine serum albumin (BSA) model where sugars (glucose, fructose, galactose, ribose) and aldehydes (glyoxal and methylglyoxal) were used as glycation agents. Aminoguanidine and N-acetylcysteine (NAC) were applied as reference glycation/free radical inhibitors. Glycation biomarkers (kynurenine, N-formylkynurenine, dityrosine as well as advanced glycation end products contents) were assessed spectrofluorometrically. Concentrations of oxidation parameters (total thiols (TTs), protein carbonyls (PCs) and also advanced oxidation protein products (AOPPs) levels) were determined spectrophotometrically. RESULTS: We demonstrated that trazodone poorly scavenged radicals (hydroxyl radical, nitric oxide, hydrogen peroxide and 2,2-diphenyl-1-picrylhydrazyl radical) and showed low ferrous ion chelating, unlike aminoguanidine and NAC. Sugars/aldehydes caused enhancement of glycation parameters, as well as a decrease of TTs and an increase of PCs and AOPPs levels compared to BSA incubated alone. Trazodone did not reduce oxidation parameters to the baseline (BSA) and significantly exacerbated glycation markers in comparison with both BSA and BSA+glycators. The content of glycation products was markedly lower in aminoguanidine and NAC than in trazodone. The molecular docking of trazodone to BSA revealed its very low affinity, which may indicate non-specific binding of trazodone, facilitating the attachment of glycation factors. CONCLUSION: According to our findings, it may be concluded that trazodone poorly counteracts oxidation and intensifies glycation in vitro. A possible mechanism for antiglycoxidative effect of trazodone in vivo may be the enhancement of the body's adaptive response, as indicated by the results of our systematic review.

PK/PD analysis of trazodone and gabapentin in neuropathic pain rodent models: Translational PK-PD modeling from nonclinical to clinical development.

A pharmacokinetic/pharmacodynamic (PK/PD) model was developed to describe the time course of writhings after intraperitoneal injection of acetic acid in mice. The model was applied to investigate the antinociceptive effect of trazodone and gabapentin alone and in combination. Writhings time course was described by a transit compartment model with the delay due to the transit of the acetic acid being represented by a chain of intermediate compartments. In the drug-treated animals, the number of writhings decreases according to a k2 factor linking drug concentration and antinociceptive effect. Compounds' potency parameters were 10.9 and 0.0459 L/µmoles/min for trazodone and gabapentin, respectively, indicating a much higher in vivo potency of trazodone in the PD writhing test. The PK/PD parameters were used to simulate the expected writhing counts in mice at combined doses without efficacy alone, assuming pharmacological additivity. Simulation results indicated that, at low dose combinations, experimental data were mostly below the simulated writhings median, suggesting possible synergic effect. Such hypothesis was tested by adding the γ parameter in the PK/PD model to represent the deviation from the assumption of no-interaction, leading to a reduction of the objective function compared to the additive model. On this basis, several simulations were performed to identify possible starting dose combinations of trazodone and gabapentin in humans, by selecting doses yielding systemic exposures close to those being synergic in the mouse. Simulations indicated that doses of 50-100 mg trazodone could enhance gabapentin antinociceptive effect in humans, supporting the development of a low dose combination for optimal analgesia treatment.

EFFECTS OF A SINGLE ORAL DOSE OF TRAZODONE ON BEHAVIOR AND SERUM CORTISOL LEVELS IN BLUE WILDEBEEST (CONNOCHAETES TAURINUS).

Trazodone is a dose-dependent serotonin antagonist and agonist used to treat anxiety-related conditions. Trauma has been identified as the leading cause of morbidity and mortality in several nondomestic ruminant species and can be exacerbated by stress. In a recent study in domestic goats (Capra aegagrus hircus), trazodone reduced activity levels without adverse effects. Trazodone could allow for safer capture and handling in nondomestic ruminant species. The objectives of this study were to identify a dose of trazodone that decreases activity levels in captive blue wildebeest (Connochaetes taurinus) and to evaluate its safety and its effects on serum cortisol levels following a routine veterinary procedure. A pilot study using ethograms identified a group fed 15 mg/kg oral dose of trazodone as effective to reduce activity levels. Over 6 h, this dose resulted in a 111% increase in time spent sleeping or resting (P = 0.0003), a 41% increase in time spent lying down (P = 0.0016), a 64% reduction in time spent moving (P= 0.005), and a 65% reduction in time spent being vigilant (P= 0.026). Systemic absorption of trazodone was identified when plasma concentrations were measured after 2 h (95 ± 48 µg/L). Serum cortisol levels during a routine venipuncture event were not significantly different following trazodone administration (P > 0.05). Mild hyporexia was the only adverse effect noted at 15 mg/kg and was absent at a 12 mg/kg dose. Trazodone appears safe and promising to decrease activity in blue wildebeest and might thus have a positive effect on nondomestic ruminant welfare and the safety of veterinary procedures.

New, Eco-Friendly Method for Synthesis of 3-Chlorophenyl and 1,1'-Biphenyl Piperazinylhexyl Trazodone Analogues with Dual 5-HT1A/5-HT7 Affinity and Its Antidepressant-like Activity.

Serotonin 5-HT1A and 5-HT7 receptors play an important role in the pathogenesis and pharmacotherapy of depression. Previously identified N-hexyl trazodone derivatives, 2-(6-(4-(3-chlorophenyl)piperazin-1-yl)hexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one hydrochloride (7a·HCl), with high affinity for 5-HT1AR and 2-(6-(4-([1,1'-biphenyl]-2-yl)piperazin-1-yl)hexyl)-[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one hydrochloride (7b·HCl), a dual-acting 5-HT1A/5-HT7 receptor ligand, were prepared with a new microwave-assisted method. The protocol for the synthesis of 7a and 7b involved reductive alkylation under a mild reducing agent. We produced the final compounds with yield of 56-63% using ethanol or 51-56% in solvent-free conditions in 4 min. We then determined the 5-HT7R binding mode for compounds 7a and 7b using in silico methods and assessed the preliminary ADME and safety properties (hepatotoxicity and CYP3A4 inhibition) using in vitro methods for 7a·HCl and 7b·HCl. Furthermore, we evaluated antidepressant-like activity of the dual antagonist of 5-HT1A/5-HT7 receptors (7b·HCl) in the forced swim test (FST) in mice. The 5-HT1AR ligand (7a·HCl) with a much lower affinity for 5-HT7R compared to that of 7b·HCl was tested comparatively. Both compounds showed antidepressant activity, while 5-HT1A/5-HT7 double antagonist 7b·HCl showed a stronger and more specific response.

Chronic Trazodone and Citalopram Treatments Increase Trophic Factor and Circadian Rhythm Gene Expression in Rat Brain Regions Relevant for Antidepressant Efficacy.

Trazodone is an efficacious atypical antidepressant acting both as an SSRI and a 5HT2A and 5HT2C antagonist. Antagonism to H1-histaminergic and alpha1-adrenergic receptors is responsible for a sleep-promoting action. We studied long-term gene expression modulations induced by chronic trazodone to investigate the molecular underpinning of trazodone efficacy. Rats received acute or chronic treatment with trazodone or citalopram. mRNA expression of growth factor and circadian rhythm genes was evaluated by qPCR in the prefrontal cortex (PFCx), hippocampus, Nucleus Accumbens (NAc), amygdala, and hypothalamus. CREB levels and phosphorylation state were evaluated using Western blotting. BDNF levels were significantly increased in PFCx and hippocampus by trazodone and in the NAc and hypothalamus by citalopram. Likewise, TrkB receptor levels augmented in the PFCx after trazodone and in the amygdala after citalopram. FGF-2 and FGFR2 levels were higher after trazodone in the PFCx. The CREB phosphorylation state was increased by chronic trazodone in the PFCx, hippocampus, and hypothalamus. Bmal1 and Per1 were increased by both antidepressants after acute and chronic treatments, while Per2 levels were specifically augmented by chronic trazodone in the PFCx and NAc, and by citalopram in the PFCx, amygdala, and NAc. These findings show that trazodone affects the expression of neurotrophic factors involved in antidepressant responses and alters circadian rhythm genes implicated in the pathophysiology of depression, thus shedding light on trazodone's molecular mechanism of action.

Presynaptic 5-HT2A-mGlu2/3 Receptor-Receptor Crosstalk in the Prefrontal Cortex: Metamodulation of Glutamate Exocytosis.

The glutamatergic nerve endings of a rat prefrontal cortex (PFc) possess presynaptic 5-HT2A heteroreceptors and mGlu2/3 autoreceptors, whose activation inhibits glutamate exocytosis, and is measured as 15 mM KCl-evoked [3H]D-aspartate ([3H]D-asp) release (which mimics glutamate exocytosis). The concomitant activation of the two receptors nulls their inhibitory activities, whereas blockade of the 5-HT2A heteroreceptors with MDL11,939 (1 µM) strengthens the inhibitory effect elicited by the mGlu2/3 receptor agonist LY329268 (1 µM). 5-HT2A receptor antagonists (MDL11,939; ketanserin; trazodone) amplify the impact of low (3 nM) LY379268. Clozapine (0.1-10 µM) mimics the 5-HT2A agonist (±) DOI and inhibits the KCl-evoked [3H]D-asp overflow in a MDL11,939-dependent fashion, but does not modify the (±) DOI-induced effect. mGlu2 and 5-HT2A proteins do not co-immunoprecipitate from synaptosomal lysates, nor does the incubation of PFc synaptosomes with MDL11,939 (1 µM) or clozapine (10 µM) modify the insertion of mGlu2 subunits in synaptosomal plasma membranes. In conclusion, 5-HT2A and mGlu2/3 receptors colocalize, but do not physically associate, in PFc glutamatergic terminals, where they functionally interact in an antagonist-like fashion to control glutamate exocytosis. The mGlu2/3-5-HT2A metamodulation could be relevant to therapy for central neuropsychiatric disorders, including schizophrenia, but also unveil cellular events accounting for their development, which also influence the responsiveness to drugs regimens.

Effects of trazodone administration on the neurologic examination in healthy dogs.

BACKGROUND: Trazodone is an anxiolytic used PO to decrease anxiety in dogs. Whether or not trazodone affects the neurologic examination in dogs has not been previously reported. OBJECTIVE: Investigate whether trazodone administration is associated with changes in the neurologic examination in healthy dogs. ANIMALS: Thirty-two healthy dogs between 1 and 6 years old with no previously diagnosed medical conditions and perceived by their owners as neurologically normal. METHODS: Baseline sedation and anxiety assessments and neurologic examination were performed on each dog, followed by trazodone administration (6.25-8.60 mg/kg PO). The sedation and anxiety assessments and neurologic examination were repeated 2.5 hours after trazodone administration. The examinations were performed by a single board-certified veterinary neurologist and were video-recorded. The videos were randomized and reviewed by a different neurologist, blinded to the previous evaluations, who scored the examinations. RESULTS: Seven of 32 (22%) dogs had worse scores on their neurologic examination after receiving trazodone, manifesting as new or progressive PR deficits. Although not clinically relevant, 18.7% of the dogs had consciousness levels that changed from bright, alert, responsive to quiet, alert, responsive after trazodone administration. No other changes were observed on neurologic examination. Sedation and anxiety scores were significantly different after trazodone administration compared to before (P < .001 and P < .001, respectively). CONCLUSIONS AND CLINICAL IMPORTANCE: Most dogs did not have changes on neurologic examination after trazodone administration. However, approximately 20% of dogs had new or worsening PR deficits after receiving trazodone. Ideally, trazodone should not be given before neurologic examination in dogs.

Thyrotropin-releasing hormone analog as a stable upper airway-preferring respiratory stimulant with arousal properties.

Taltirelin is a stable, brain-penetrating thyrotropin-releasing hormone (TRH) analog with minimal endocrine activity and potential respiratory stimulant properties. Taltirelin's receptor target shows high differential expression at the hypoglossal motor nucleus, and local taltirelin microperfusion into the hypoglossal motor nucleus causes sustained tongue motor activation compared with the transient activating effects of TRH itself. Here, we performed a randomized, within-subject, repeated-measures design over six separate study days (separated by at least 72 h) in chronically instrumented male (n = 10) and female (n = 9) rats to identify effects on sleep and breathing. Vehicle controls or taltirelin (0.1 and 1 mg/kg) with and without trazodone (30 mg/kg) were administered by intraperitoneal injection. Trazodone was included due to clinical interest in the context of sleep apnea pharmacotherapy as it can suppress arousal without compromising pharyngeal muscle activity. Systemically administered taltirelin (1 but not 0.1 mg/kg) increased tonic and within-breath phasic tonic muscle activity compared with vehicle controls (P ≤ 0.007), with little or no changes in diaphragm amplitude or respiratory rate. Taltirelin also suppressed nonrapid eye movement (non-REM) sleep and increased wakefulness (P ≤ 0.037). Other indices of taltirelin-induced central nervous system arousal included increased trapezius muscle tone in non-REM sleep and decreased total electroencephalogram power and δ (0.5-4 Hz) power (P ≤ 0.046). These effects were especially apparent in non-REM sleep and not prevented by trazodone. These preclinical findings identify taltirelin as a stable upper airway-preferring respiratory stimulant with arousal properties, traits that have potential favorable relevance to some respiratory disorders but not others.NEW & NOTEWORTHY One of the major goals for translational sleep science and medicine is to identify viable and tractable pharmacological targets for obstructive sleep apnea and other respiratory disorders of sleep or sedation. In the present preclinical study in rats, we performed a randomized, within-subject, repeated-measures design over six intervention study days in chronically instrumented male and female rats with systemic peripheral administration of vehicle controls, the thyrotropin-releasing hormone analog taltirelin at two doses, all with and without coadministered trazodone. Trazodone was included due to clinical interest in the context of sleep apnea pharmacotherapy as it can suppress arousal without compromising pharyngeal muscle activity. These preclinical findings newly identify taltirelin as a stable upper airway-preferring respiratory stimulant with arousal properties. These traits have potential favorable relevance to some respiratory disorders but not others, as identified and discussed.

Trazodone and patient outcomes in dementia-Limitations of naturalistic cohort data.

The unfolded protein response has been increasingly implicated as an important pathological pathway and target for therapeutic intervention in neurodegeneration. The licensed antidepressant trazodone is one drug which has been proposed to act on this pathway and may therefore be a potential therapy. Previous examination of existing data for patients with dementia prescribed trazodone did not find a signal suggesting a disease modifying effect. Here we add to that literature by examining the electronic patient record of patients with dementia in Cambridgeshire UK. We found that trazodone is rarely prescribed and where it is used it is at a dose less than half that predicted to be disease modifying. We also found that patients prescribed trazodone had higher levels of neuropsychiatric symptoms and were relatively late in the disease course, likely beyond the optimal point for therapeutic intervention. We suggest it is therefore premature to discard potential therapies based on observational data alone, particularly when experimental medicine approaches to examine the effects of trazodone are feasible.

Effects of gabapentin and trazodone on electroretinographic responses in clinically normal dogs.

OBJECTIVE: To compare electroretinographic (ERG) responses obtained in dogs before and after oral administration of gabapentin, trazodone, and a combination of both medications. ANIMALS: 12 clinically normal dogs. PROCEDURES: A short-protocol ERG with 20 minutes of dark adaption was recorded for all dogs to establish baseline ERG responses. Dogs then received gabapentin (approx 30 mg/kg), trazadone (approx 20 mg/kg or approx 5 mg/kg), or a combination of gabapentin (approx 20 mg/kg) and trazodone (approx 5 mg/kg) orally, and the same ERG protocol was repeated 2 hours later. Dogs were given a washout period of at least 1 week between treatments. RESULTS: a-Wave amplitudes were significantly (P = 0.018) decreased after administration of the combination of gabapentin and trazodone. b-Wave amplitudes were significantly decreased after administration of the 20-mg/kg dose of trazodone (P = 0.006) and after administration of the combination of gabapentin and trazodone (P = 0.002). Heavier dogs that received higher total doses of trazodone had decreases in a-wave amplitude after administration of the 20-mg/kg dose of trazodone and in b-wave amplitude after administration of the 5-mg/kg dose of trazodone. CLINICAL RELEVANCE: High doses of trazodone and the combination of gabapentin and trazodone significantly decreased a-wave and b-wave amplitudes in clinically normal dogs. However, the effects on retinal responses had little clinical importance. Therefore, these medications can be used safely in a clinical setting; however, further studies are needed in dogs with retinal disease.

The effect of preanaesthetic oral trazodone hydrochloride on the induction dose of propofol: a preliminary retrospective study.

OBJECTIVE: To determine whether the administration of trazodone to dogs 2 hours prior to radiotherapy treatment reduced the dose of propofol required to induce anaesthesia. STUDY DESIGN: Retrospective, crossover, case-matched study. ANIMALS: Records of 30 client-owned dogs. METHODS: Anaesthetic records from all dogs undergoing weekly radiotherapy treatment between January 2020 and December 2020 were retrospectively assessed. All dogs were premedicated with 10 µg kg-1 alfentanil and 12 µg kg-1 atropine intravenously (IV) and anaesthesia was induced with IV propofol. In part 1, the propofol induction dose was compared between anaesthetics when trazodone was administered prior to the anaesthetic (T) versus not (NT). For part 2, control dogs not administered trazodone during the treatment course were case-matched based on bodyweight and tumour location and type. The propofol induction dose was compared between the first (C1) and last (C2) anaesthetic to identify the effects of confounding factors. A Wilcoxon signed-rank test for repeated measurements was performed to identify any significant differences in the propofol induction dose between NT and T in the study dogs and between C1 and C2 in the control dogs. RESULTS: In part 1, 15 study dogs that were administered trazodone prior to at least one anaesthetic were identified. A significant difference in propofol induction dose between groups NT and T was identified [3.3 (2.1-7.4) and 2.0 (1.5-5.0) mg kg-1, respectively; p = 0.003]. In part 2, 15 dogs were case-matched to the study cohort. The dose of propofol administered did not differ between the first and last anaesthetic [2.5 (1.6-6.4) and 2.6 (1.9-8.9) mg kg-1, respectively; p = 0.638]. CONCLUSIONS AND CLINICAL RELEVANCE: Preanaesthetic trazodone administration reduced the induction dose of propofol compared to when it was not administered to dogs following premedication with IV atropine and alfentanil.