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 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.

PHARMACOKINETICS AND CLINICAL EFFECTS OF A SINGLE ORAL DOSE OF TRAZODONE IN THE DOMESTIC GOAT (CAPRA HIRCUS) AS A MODEL FOR WILD RUMINANTS.

Trazodone is an antianxiety medication commonly used in human and veterinary medicine. Stress-related trauma is the leading cause of morbidity and mortality in wild ruminant species. Trazodone could reduce stress and allow safer capture and handling, thus having a positive effect on their welfare. The objective of this study was to describe the clinical effects and pharmacokinetic profile of an oral dose of trazodone in domestic goats (Capra hircus) as a model for wild ruminants. A pilot study using ethograms and accelerometers identified an oral dose of 10 mg/kg as optimal to reduce activity levels. This dose resulted in a 502% increase in time spent sleeping (P=0.0016) and a 623% increase in time spent lying down (P=0.01). Additionally, there were reductions of 72% in time spent grooming (P=0.02), 49% in time spent moving (P=0.01), and 87% in time spent observing (P=0.0002). Activity levels were significantly decreased by 31% for 4 hr following administration (P=0.049). There were no observed adverse effects. Time spent eating or ruminating was not affected by trazodone administration (P > 0.05). The pharmacokinetics of trazodone following a single oral dose of 10 mg/kg in 7 goats was assessed. All animals achieved plasma concentrations over 130 ng/ml, a level considered therapeutic in humans and dogs, for a mean of 6.4 ± 5.0 hr. Mean terminal half-life was 10.55 ± 6.80 hr. All goats achieved maximum concentration within 5-15 min and still had detectable plasma levels at 24 hr. Trazodone appears promising to decrease stress in exotic ruminant species. Further research is warranted to establish its efficacy in other ruminant species and clinical situations.

Clinical guidance for the use of trazodone in major depressive disorder and concomitant conditions: pharmacology and clinical practice.

AIM: To provide a review of the clinically relevant evidence pertaining to the use of trazodone in major depressive disorder. METHODS: Medline and Cochrane Library searches were searched using the keywords 'trazodone' AND 'depression', to identify the most relevant literature pertinent to the pharmacological properties of trazodone and its use in clinical practice. Articles that were selected included basic pharmacology papers, clinical trials, clinical practice guidelines, and reviews. Related references were cross checked. European and United States prescribing information was reviewed as well. An effort was made to give weight to the information that was most relevant for daily clinical practice. RESULTS: Trazodone is an antidepressant with a mechanism of action that remains innovative and with a favorable profile for the treatment of depression. The appropriate antidepressant doses are usually 150-300 mg/day and are often higher than the doses that are used when trazodone is prescribed to augment the antidepressant effect of another medication, for instance when trazodone is prescribed to address insomnia in a patient treated with an SSRI. Trazodone is usually well tolerated and has a low risk of anticholinergic side effects, weight gain and sexual side effects. DISCUSSION: Trazodone is an established medication that is efficacious for the treatment of a broad array of depressive symptoms, including symptoms that are less likely to respond to other antidepressants (e.g. SSRI), such as insomnia. As an antidepressant, trazodone has proven as efficacious as the tricyclic and second-generation antidepressants and is tolerated relatively well. Trazodone may be helpful for patients with major depression and comorbid insomnia, anxiety or psychomotor agitation. CONCLUSIONS: Trazodone is efficacious antidepressants with a relatively low risks of side effects such as weight gain, sexual or anticholinergic effects (such as constipation, urinary retention, dry mouth). In addition to being able to control a wide range of depressive symptoms, trazodone may improve sleep and be particularly helpful for patients whose symptoms of depression include insomnia.

Uptake and metabolism of the antidepressants sertraline, clomipramine, and trazodone in a garden cress (Lepidium sativum) model.

Environmental contamination with pharmaceuticals has received growing attention in recent years. Several studies describe the presence of traces of drugs in water bodies and soils and their impacts on nontarget organisms including plants. Due to these facts investigations of the uptake and metabolism of pharmaceuticals in organisms is an emerging research area. The present study demonstrates the analysis of three selected antidepressants (sertraline, clomipramine, and trazodone) as well as metabolites and transformation products in a cress model (Lepidium sativum). Cress was treated with tap water containing 10 mg/L of the parent drugs. Employing an analytical approach based on high performance liquid chromatography coupled with quadrupole time of flight or Orbitrap mass spectrometry in MS and MS² modes, in total 14 substances were identified in the cress extracts. All three parent drugs were taken up by the cress and translocated from the roots to the leaves in specific patterns. In addition to this, eleven metabolite species were identified. They were generated by hydroxylation, demethylation, conjugation with amino acids, or combinations of these mechanisms. Finally, the inclusion of control cultures in the experimental setup allowed for a differentiation of "true" metabolites generated by the cress and transformation products generated by plant-independent mechanisms.

Evaluating the Role of Drug Metabolism and Reactive Intermediates in Trazodone-Induced Cytotoxicity toward Freshly-Isolated Rat Hepatocytes.

Background: Trazodone is an antidepressant agent widely administered for the treatment of depressive disorders. On the other hand, several cases of hepatic injury have been reported after Trazodone administration. Although the precise mechanism(s) of trazodone-induced liver injury is not known, some investigations proposed the role of reactive intermediates in this complication. This study was designed to investigate the role of reactive metabolites in hepatocytes injury induced by trazodone. Methods: Isolated rat hepatocytes were prepared by the method of collagenase enzyme perfusion via the portal vein. Cells were treated with trazodone, its cytotoxic metabolite, and different enzyme inhibitors and cytoprotective agents. Results: It was found that trazodone was toxic towards hepatocytes and caused 50% cell death after 2 h of incubation at a dose of 450 µM. The trazodone postulated reactive metabolite; m-chlorophenyl piperazine (m-CPP) was less toxic and caused 50% cell death at a dose of 750 µM at a similar time period. Cellular glutathione (GSH) depletion and lipid peroxidation were detected when hepatocytes were treated with trazodone and/or m-CPP. Depleting hepatocytes GSH beforehand, increased cytotoxicity of both trazodone and m-CPP. Troleandomycin as the CYP3A4 inhibitor prevented cytotoxicity of trazodone but slightly affected m-CPP-induced cell injury. Inhibition of CYP2D6 by quinidine and cimetidine increased the cytotoxicity of both trazodone and m-CPP. Antioxidants and ATP suppliers slightly prevented cytotoxicity of trazodone and m-CPP. Conclusion: As inhibitors of CYP3A4 and 2D6 affected trazodone cytotoxicity, it is suggested that trazodone -induced cytotoxicity, at least in part, is mediated by its reactive metabolites.

General unknown screening procedure for the characterization of human drug metabolites in forensic toxicology: applications and constraints.

LC coupled to single (LC-MS) and tandem (LC-MS/MS) mass spectrometry is recognized as the most powerful analytical tools for metabolic studies in drug discovery. In this article, we describe five cases illustrating the utility of screening xenobiotic metabolites in routine analysis of forensic samples using LC-MS/MS. Analyses were performed using a previously published LC-MS/MS general unknown screening (GUS) procedure developed using a hybrid linear IT-tandem mass spectrometer. In each of the cases presented, the presence of metabolites of xenobiotics was suspected after analyzing urine samples. In two cases, the parent drug was also detected and the metabolites were merely useful to confirm drug intake, but in three other cases, metabolite detection was of actual forensic interest. The presented results indicate that: (i) the GUS procedure developed is useful to detect a large variety of drug metabolites, which would have been hardly detected using targeted methods in the context of clinical or forensic toxicology; (ii) metabolite structure can generally be inferred from their "enhanced" product ion scan spectra; and (iii) structure confirmation can be achieved through in vitro metabolic experiments or through the analysis of urine samples from individuals taking the parent drug.

Detection of novel reactive metabolites of trazodone: evidence for CYP2D6-mediated bioactivation of m-chlorophenylpiperazine.

Several new glutathione adducts (M3-M7) of trazodone were tentatively identified in human liver microsomal incubations using liquid chromatography-tandem mass spectrometry (LC/MS/MS). Following incubations with trazodone in the presence of glutathione, 1-(3'-chlorophenyl)piperazine (m-CPP), a major circulating and pharmacologically active metabolite of several antidepressants including trazodone, nefazodone, and etoperidone, was trapped with glutathione to afford the corresponding quinone imine-sulfydryl adducts M4 and M5. Two novel glutathione adducts of deschloro-m-CPP and deschloro-trazodone, M3 and M6, were also detected by tandem mass spectrometry. The identities of these m-CPP-derived glutathione adducts were further confirmed by LC/MS/MS analyses of microsomal incubations of m-CPP. To investigate the bioactivation mechanism, a regioisomer of m-CPP, 1-(4'-chlorophenyl)piperazine, was incubated in human liver microsomes. Blockage of bioactivation by 4'-chloro-substitution at least partially suggested that formation of m-CPP-derived glutathione adducts M3, M4, and M5 is mediated by a common quinone imine intermediate. A tentative pathway states that upon formation of the trazodone- and m-CPP-1',4'-quinone imine intermediates through initial 4'-hydroxylation, glutathione attacks at the chlorine position by an ipso substitution, resulting in 4'-hydroxy-3'-glutathion-deschloro-trazodone (M6) and 4'-hydroxy-3'-glutathion-deschloro-m-CPP (M3), respectively. In contrast to CYP3A4-dependent bioactivation of trazodone itself, formation of M4 was mediated specifically by CYP2D6, as evidenced by cDNA-expressed CYP2D6-catalyzing formation of M4 from m-CPP, strong inhibition of formation of M4 by quinidine, a specific CYP2D6 inhibitor, in both incubations of trazodone and m-CPP with human liver microsomes, and concentration-dependent inhibition of M4 formation by quinidine.

Piperazine-derived designer drug 1-(3-chlorophenyl)piperazine (mCPP): GC-MS studies on its metabolism and its toxicological detection in rat urine including analytical differentiation from its precursor drugs trazodone and nefazodone.

Studies on the metabolism and the toxicological analysis of the piperazine-derived designer drug 1-(3-chlorophenyl)piperazine (mCPP) in rat urine using gas chromatography-mass spectrometry (GC-MS) are described. mCPP was extensively metabolized, mainly by hydroxylation of the aromatic ring and by degradation of the piperazine moiety to the following metabolites: two hydroxy-mCPP isomers, N-(3-chlorophenyl)ethylenediamine, 3-chloroaniline, and two hydroxy-3-chloroaniline isomers. The hydroxy-mCPP metabolites were partially excreted as the corresponding glucuronides and/or sulfates, and the aniline derivatives were partially acetylated to N-acetyl-hydroxy-3-chloroaniline isomers and N-acetyl-3-chloroaniline. Our systematic toxicological analysis (STA) procedure using full-scan GC-MS after acid hydrolysis, liquid-liquid extraction, and microwave-assisted acetylation allowed the detection of mCPP and its previously mentioned metabolites in rat urine after single administration of a dose calculated from the doses commonly taken by drug users. The hydroxy-mCPP metabolites should be used as target analytes being the major metabolites of mCPP. Assuming similar metabolism, our STA procedure should be suitable for detection of an intake of mCPP in human urine. Furthermore, possibilities for differentiating an intake of mCPP from that of its precursor drugs trazodone or nefazodone, two common antidepressants, are described. Within the context of these studies, N-(3-chlorophenyl)ethylenediamine was identified as a new metabolite of these two antidepressants.

In vitro identification of metabolic pathways and cytochrome P450 enzymes involved in the metabolism of etoperidone.

1. In vitro studies have been carried out to investigate the metabolic pathways and identify the hepatic cytochrome P450 (CYP) enzymes involved in etoperidone (Et) metabolism. 2. Ten in vitro metabolites were profiled, quantified and tentatively identified after incubation with human hepatic S9 fractions. Et was metabolized via three metabolic pathways: (A) alkyl hydroxylation to form OH-ethyl-Et (M1); (B) phenyl hydroxylation to form OH-phenyl-Et (M2); and (C) N-dealkylation to form 1-m-chlorophenylpiperazine (mCPP, M8) and triazole propyl aldehyde (M6). Six additional metabolites were formed by further metabolism of M1, M2, M6 and M8. 3. Kinetic studies revealed that all metabolic pathways were monophasic, and the pathway leading to the formation of OH-ethyl-Et was the most efficient at eliminating the drug. On incubation with microsomes expressing individual recombinant CYPs, formation rates of M1-3 and M8 were 10-100-fold greater for CYP3A4 than that for other CYP forms. The formation of these metabolites was markedly inhibited by the CYP3A4-specific inhibitor ketoconazole, whereas other CYP-specific inhibitors did not show significant effects. In addition, the production of M1-3 and M8 was strongly correlated with CYP3A4-mediated testosterone 6beta-hydroxylase activities in 13 different human liver microsome samples. 4. Dealkylation of the major metabolite M1 to form mCPP (M8) was also investigated using microsomes containing recombinant CYP enzymes. The rate of conversion of M1 to mCPP by CYP3A4 was 503.0 +/- 3.1 pmole nmole(-1) min(-1). Metabolism of M1 to M8 by other CYP enzymes was insignificant. In addition, this metabolism in human liver microsomes was extensively inhibited by the CYP3A4 inhibitor ketoconazole, but not by other CYP-specific inhibitors. In addition, conversion of M1 to M8 was highly correlated with CYP3A4-mediated testosterone 6beta-hydroxylase activity. 5. The results strongly suggest that CYP3A4 is the predominant enzyme-metabolizing Et in humans.

Relationship between plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine, and its clinical effect in depressed patients.

Relationships between plasma concentrations of trazodone and m-chlorophenylpiperazine (m-CPP) and the clinical effects were studied in 26 patients (12 males and 14 females) with major depression during three weeks' treatment of 150 mg/d trazodone using an open-study design. Depressive symptoms were evaluated by Montgomery Asberg Depression Rating Scale (MADRS), and subjective side effects were assessed by UKU side effects rating scale (UKU) before treatment and at weekly intervals. Plasma concentrations of trazodone and m-CPP were measured by HPLC. There were significant linear relationships between the steady-state plasma concentration (Css) of trazodone and both the final MADRS score (rs = -0.529, P < 0.01) and the percent improvement at 3 weeks (r = 0.442, P < 0.05). Moreover, the proportion of responders (a final MADRS score of 10 or less) was significantly higher in the group with a trazodone concentration greater than 714 ng/mL (6/8 vs 3/18, P = 0.008). No significant correlation was found between UKU score and the Css for either compound nor between the UKU score and the ratio of m-CPP/trazodone. The current study suggests that a therapeutic response is dependent on the plasma concentration of trazodone but not m-CPP and that a plasma trazodone concentration of about 700 ng/mL may be a threshold for a good therapeutic response.

Effects of genetic polymorphism of CYP1A2 inducibility on the steady-state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine in depressed Japanese patients.

The effects of a genetic polymorphism of inducibility of cytochrome P450 (CYP) 1A2 on the steady-state plasma concentrations of trazodone and its active metabolite, m-chlorophenylpiperazine, were studied in order to clarify if these steady-state plasma concentrations are dependent on the CYP1A2 polymorphism. Fifty-eight Japanese depressed patients received trazodone 150 mg/day at bedtime. The steady-state plasma concentrations of trazodone and m-chlorophenylpiperazine were measured in duplicate using high performance liquid chromatographic method, and were corrected to the mean body weight for analyses. A point mutation from guanine (wild type) to adenine (mutated type) at position -2964 in the 5'-flanking region of CYP1A2 gene was identified by polymerase chain reaction fragment length polymorphism method. The mean steady-state plasma concentration of trazodone, but not m-chlorophenylpiperazine was significantly (P<0.05) lower in smokers than in non-smokers. Twenty-two smokers had 16 homozygotes of the wild type allele, 5 heterozygotes of the wild type and mutated alleles, and one homozygote of the mutated allele. There was no significant difference in the mean steady-state plasma concentration of trazodone or m-chlorophenylpiperazine between smokers with no mutation and those with mutation, although one homozygote of the mutated allele had the highest steady-state plasma concentration of trazodone in smokers. The present study thus suggests that CYP1A2 polymorphism does not necessarily have predictive value of the steady-state plasma concentration of trazodone or m-chlorophenylpiperazine in most of the smokers treated with trazodone.

Evaluation of the absorption, excretion and metabolism of [14C] etoperidone in man.

1. The absorption, excretion and metabolism of 2-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-4,5-diethyl-2,4-dihydro-3H-1,2,4- triazole-3-one hydrochloride (etoperidone HCl) was investigated in six healthy men. Subjects were tasted overnight before receiving a single oral dose of a 100 mg solution [14C] etoperidone HCl. 2. Plasma (0-48 h), urine (0-120 h) and faecal (0-120 h) samples were collected. The terminal half-life of the total radioactivity from plasma was 21.7 +/- 2.8h with an apparent clearance of 1.01 +/- 0.08 ml min(-1). Recoveries of total radioactivity in urine and faeces were 78.8 +/- 3.6% and 9.6 +/- 4.1% of the dose, respectively. 3. Etoperidone and 21 metabolites were isolated and identified in the plasma, urine and faecal extracts. Unchanged etoperidone accounted for <0.01% of the dose in all excreta samples. Nine metabolites were identified in the plasma extracts and 21 urinary metabolites were identified. Seven faecal metabolites were identified. 4. Five proposed pathways were used to describe the formation of the metabolites: alkyl oxidation, piperazinyl oxidation, N-dealkylation, phenyl hydroxylation and conjugation. Alkyl oxidation of etoperidone resulted in the formation of 2-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-4-ethyl-2,4-dihydro-5- (1-hydroxyethyl)-3H-1,2,4-triazole-3-one. Piperazinyl oxidation of this metabolite leads to the formation of its N-oxide. N-dealkylation of the piperazinyl group led to the formation of 1-(3-chlorophenyl) piperazine and triazole propionic acid. Phenyl hydroxylation led to three important metabolites in the urine and faeces.

Effects of trazodone on neurotransmitter release from rat mossy fibre cerebellar synaptosomes.

The effects of trazodone and putative sigma (sigma) receptor ligands were investigated on KCl-stimulated release of glutamate (Glu) and gamma-aminobutyric acid (GABA) from cerebellar mossy fibre synaptosomes. Both trazodone and serotonin (5-HT) inhibited the increase of Glu and GABA release evoked by 15 mM KCl. Trazodone increased the inhibition of Glu release caused by 0.01 microM 5-HT, while it antagonized the inhibition induced by higher 5-HT concentrations. Despite the low affinity of trazodone for both sigma(1) and sigma(2) binding sites, with a pK(i) of 5.9 and 6.0 respectively, two sigma receptor ligands, (+)-3-[3-hydroxypheny]-N-(1-propyl)piperidine ((+)-3-PPP) and N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino)ethylamine (BD 1047) antagonized the effects of trazodone. The putative sigma receptor ligand N-allylnormetazocine ((+)-SKF 10,047) mimicked the inhibitory effect of trazodone. As with trazodone, (+)-3-PPP and BD 1047 antagonized the activity of (+)-SKF 10,047 but not that of 5-HT. On the whole, these results suggest that trazodone shares a common molecular target with sigma compounds distinct from that of 5-HT and is involved in K(+)-stimulated Glu and GABA release from mossy fibre cerebellar synaptosomes.

Affinity of trazodone for human penile alpha1- andalpha2-adrenoceptors.

OBJECTIVE: To determine the affinities of human penile alpha-adrenoceptors and cloned human alpha-adrenoceptor subtypes for trazodone, an antidepressant with reported beneficial effects in erectile dysfunction. Materials and methods Competition radioligand binding studies were performed with trazodone in human penile tissue and in cell lines stably expressing all cloned human alpha-adrenoceptor subtypes. RESULTS: Trazodone had higher affinity for human alpha1-adrenoceptors (10-130 nmol/L) than for alpha2-adrenoceptors (300-700 nmol/L), but did not discriminate between subtypes of human alpha1- or alpha2-adrenoceptors. CONCLUSION: Trazodone has high and moderate affinity for human alpha1- and alpha2-adrenoceptors, respectively; this might contribute to its reported beneficial effects in erectile dysfunction.

In vitro metabolism of trazodone by CYP3A: inhibition by ketoconazole and human immunodeficiency viral protease inhibitors.

BACKGROUND: Pharmacologic treatment of emotional disorders in HIV-infected patients can be more easily optimized by understanding of potential interactions of psychotropic drugs with medications used to treat HIV infection and its sequelae. METHODS: Biotransformation of the antidepressant trazodone to its principal metabolite, meta-chlorophenylpiperazine (mCPP), was studied in vitro using human liver microsomes and heterologously expressed individual human cytochromes. Interactions of trazodone with the azole antifungal agent, ketoconazole, and with human immunodeficiency virus protease inhibitors (HIVPIs) were studied in the same system. RESULTS: Formation of mCPP from trazodone in liver microsomes had a mean (+/- SE) K(m) value of 163 (+/- 21) micromol/L. Ketoconazole, a relatively specific CYP3A inhibitor, impaired mCPP formation consistent with a competitive mechanism, having an inhibition constant (K(i)) of 0.12 (+/- 0.01) micromol/L. Among heterologously expressed human cytochromes, only CYP3A4 mediated formation of mCPP from trazodone; the K(m) was 180 micromol/L, consistent with the value in microsomes. The HIVPI ritonavir was a potent inhibitor of mCPP formation in liver microsomes (K(i) = 0.14 +/- 0.04 micromol/L). The HIVPI indinavir was also a strong inhibitor, whereas saquinavir and nelfinavir were weaker inhibitors. CONCLUSIONS: CYP3A-mediated clearance of trazodone is inhibited by ketoconazole, ritonavir and indinavir, and indicates the likelihood of pharmacokinetic interactions in vivo.

Effect of modifications of the alkylpiperazine moiety of trazodone on 5HT2A and alpha1 receptor binding affinity.

A series of triazolopyridine derivatives (compounds 2a-l) were synthesized in order to explore the effect of modifications of the alkylpiperazine moiety of trazodone (fragment A) on binding affinity for 5HT2A and alpha1 receptors. All of the synthesized compounds show a decrease of affinity for both 5HT2A and alpha1 receptors, as compared to trazodone, with the exception of compounds 2b,c which bear a methyl group in an alpha position to the aliphatic nitrogen atom N1. These compounds showed a decrease of affinity only for the alpha1 receptor. The stereochemical influence of the piperazine moiety of compound 2c was also evaluated. Enantiomer (S)-2c showed the most significant differences between 5HT2A and alpha1 receptor affinity (IC50 values) and among the corresponding functional properties (pA2 values). Since (S)-2c cannot generate the metabolite 4-(3-chlorophenyl)piperazine this product was selected for further pharmacological studies.

Pharmacokinetic and pharmacodynamic analyses of trazodone in rat striatum by in vivo microdialysis.

The aim of this study was to investigate the brain pharmacokinetics and pharmacodynamics of trazodone. Sensitive microbore high-performance liquid chromatographic methods with electrochemical detection (LC-ED) were developed for the determination of trazodone, serotonin (5-HT), and their respective metabolites. The feasibility of microdialysis coupled with LC-ED system for direct analysis of these compounds in the rat striatum was investigated. Striatal dialysates were automatically injected onto a cyano microbore column, through an on-line injector, for the determination of trazodone and its metabolite or onto a reversed phase microbore column for the determination of 5-HT and its metabolite. A monophase phenomenon with a first-order elimination rate constant was observed for trazodone. The brain pharmacokinetics of trazodone appear to conform to a one-compartment model. Surprisingly, no significant changes in striatal 5-HT or its metabolite were observed following the same dosage and time course. The present results suggest that brain microdialysis methods may be applicable to pharmacokinetic and pharmacodynamic studies of psychotrophic agents.