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.

Drugs detection in fingerprints

Fingerprints left at a crime scene are used to connect the crime to a person who may have been present there. Fingerprints can also be used as alternative material in forensic toxicology. The detection of drugs in fingerprint samples can be used to show that an individual touching an item has consumed specific drugs. The aim of this study was to check the usefulness of fingerprints in drug analyses and detection of some analytes in this material. Fingerprint samples were collected on glass slides from a volunteer who consumed separately tablets containing pseudoephedrine, codeine, dextromethorphan, and used lidocaine spray. Moreover, fingerprints of individuals receiving sertraline, hydroxyzine and trazodone as part of their long-term treatment were analysed. The detection of drugs was conducted using the liquid chromatography tandem mass spectrometry (LC-MS/MS) technique. After administration of single doses of drugs, they were detected up to 36 h (pseudoephedrine), 24 h (codeine), and less than 6 h (dextromethorphan and lidocaine) with maximum concentrations observed at 1-4 h. In fingerprints of a person who has finished treatment with hydroxyzine and sertraline it was possible to detect these drugs even 20 days after last drug administration. Cetirizine (hydroxyzine metabolite) and mCPP (trazodone metabolite) were determined in fingerprints of individuals under long-term treatment. This work has demonstrated that forensic toxicology can use fingerprints as alternative material. Drugs can be detected in fingerprints even after their single doses. Parent compounds predominate over metabolites in the fingerprints. The detection window depends on the type of drug and duration of the treatment.

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.

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.

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 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.

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.

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.

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.

Trazodone is metabolized to m-chlorophenylpiperazine by CYP3A4 from human sources

The metabolism of the antidepressant drug trazodone to its active metabolite, m-chlorophenylpiperazine (mCPP), was studied in vitro using human liver microsomal preparations and cDNA-expressed human cytochrome P450 (P450) enzymes. The kinetics of mCPP formation from trazodone were determined, and three in vitro experiments were performed to identify the major P450 enzyme involved. Trazodone (100 microM) was incubated with 16 different human liver microsomal preparations characterized for activities of 7 different P450 isoforms. The production of mCPP correlated significantly with activity of cytochrome P4503A4 (CYP3A4) only. Trazodone (100 microM) was then incubated with microsomes from cells expressing human CYP1A1, CYP1A2, CYP2C8, CYP2C9arg, CYP2C9cys, CYP2C19, CYP2D6, or CYP3A4. Only incubations with CYP3A4 resulted in mCPP formation. In the third experiment, the CYP3A4 inhibitor ketoconazole was found to inhibit mCPP formation concentration dependently in both human liver microsomes and in microsomes from cells expressing human CYP3A4. The present results indicate that trazodone is a substrate for CYP3A4, that CYP3A4 is a major isoform involved in the production of mCPP from trazodone, and that there is the possibility of drug-drug interactions with trazodone and other substrates, inducers and/or inhibitors of CYP3A4.

Effects of various factors on steady state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine

Effects of various factors on steady state plasma concentrations of trazodone and its active metabolite m-chlorophenylpiperazine (mCPP) were studied in 43 depressed patients (19 males, 24 females) receiving trazodone 150 mg at bedtime for 1-3 weeks. Sixteen cases were smokers, and 19 cases were also receiving various benzodiazepines. The means (and ranges) of plasma concentrations of trazodone and mCPP, and the mCPP/trazodone ratio were 619 (251-1059) ng/ml, 59 (32-139) ng/ml and 0.100 (0.044-0.219), respectively. Smokers had significantly (p < 0.05) lower plasma concentrations of trazodone and higher mCPP/trazodone ratios than non-smokers. Age, sex and co-administration of benzodiazepines did not affect any plasma concentrations or the mCPP/trazodone ratio. In 11 cases where the dose was increased to 300 mg, neither plasma concentration/dose ratios nor the mCPP/trazodone ratio changed significantly. The present study thus suggests that: (1) there is a large Interindividual variation in the metabolism of trazodone; (2) smoking enhances the metabolism, but age, sex and co-administration of benzodiazepines do not affect it; (3) trazodone and mCPP have linear kinetics.

Trazodone dosing regimen: experience with single daily administration

Efficacy being constant, antidepressant choice is dictated by side effect profile, patient acceptance, and safety. Trazodone has been shown to be safe in overdose, and the side effect profile is mild, with sedation the most common side effect. Sleep electroencephalogram and clinical studies have shown trazodone effective in improving sleep in normal subjects, insomniac patients, and patients with major depression. Tolerance and rapid eye movement rebound on discontinuation do not occur. The 3- to 9-hour half-life of trazodone and its pharmacokinetics favors a dose weighted at bedtime. Studies comparing multiple daytime dosing to single dosing at bedtime have shown equal efficacy in relieving depression. At treatment onset, a single nighttime dose is more productive of sleep with less daytime drowsiness. These differences between single nighttime dosing and multiple daily dosing disappear with continued administration. Geriatric patients respond similarly. Trazodone is best dosed at 150 mg given predominantly (but not necessarily all) at bedtime and increased as needed to 200 to 300 mg for full antidepressant efficacy.

Trazodone kinetics: effect of age, gender, and obesity

Single 25 mg intravenous and 50 mg oral doses of trazodone were given to 43 healthy subjects, divided into young men and women (aged 18 to 40 years) and elderly men and women (aged 60 to 76 years). Among men, trazodone volume of distribution (Varea) was increased in elderly vs. young subjects (1.15 vs. 0.89 L/kg; P less than 0.05), and clearance decreased (1.65 vs. 2.31 ml/min/kg; P less than 0.05), thereby increasing elimination half-life (t1/2) in elderly men (8.2 vs. 4.7 hours; P less than 0.001). Varea in women was also increased in the elderly (1.5 vs. 1.27 L/kg; P less than 0.02), causing increased t1/2 (7.6 vs. 5.9 hours; P less than 0.05), but clearance was unrelated to age. Absolute bioavailability of oral trazodone averaged 70% to 90% and was unrelated to age or sex. In 23 obese subjects (mean weight 112 kg) vs. 23 matched control subjects of normal weight (mean 65 kg), Varea was greatly increased (162 vs. 67 L; 1.43 vs. 1.04 L/kg; P less than 0.001) and was highly correlated with body weight (r = 0.91). Clearance was unchanged between groups (146 vs. 136 ml/min), but the increased Varea caused prolonged t1/2 in obese subjects (13.3 vs. 5.9 hours; P less than 0.001). Reduced clearance of trazodone among elderly men may indicate a need for dosage reduction during chronic therapy. In obese individuals, choice of dosage during chronic treatment should be based on ideal rather than total body weight.

Excretion of trazodone in breast milk

The excretion of breast milk was studied in six lactating women following the oral administration of a single trazodone tablet (50 mg). The milk/plasma ratio of trazodone based on area under the plasma and milk curves was small: 0.142 +/- 0.045 (mean +/- s.d.). Assuming that the babies would drink 500 ml 12 h-1, they would be exposed to less than 0.005 mg kg-1 as compared to 0.77 mg kg-1 for the mothers. It is concluded that exposure of babies to trazodone via breast milk is very small.

A possible diurnal variation in trazodone clearance

Diurnal variations in drug metabolism that have clinical consequences have been described for several drugs used in internal medicine but have not been reported for antidepressants. The long half-lives of most antidepressants may obscure such variations. Trazodone hydrochloride has a short half-life compared with other commercially available antidepressants. The authors measured serum levels of trazodone 11 hours after both 9 a.m. and 9 p.m. equal doses of the medication in individuals who had been on these doses for more than 3 days. For patients on other medications in addition to trazodone, serum levels were significantly higher at 8 a.m. than at 8 p.m. (N = 7, P less than 0.01) and approached significance for patients on trazodone alone (N = 8, P = 0.06). Induction of hepatic microsomal enzymes by the other medications may have exaggerated the tendency for trazodone to show diurnal variations in serum levels.

Prolongation of thiopentone-induced sleep by trazodone and its metabolite, m-chlorophenylpiperazine

Trazodone and its metabolite, m-chlorophenylpiperazine (CPP) prolonged significantly thiopentone-induced sleep in mice. Neither trazodone, nor CPP changed the cerebral concentrations of thiopentone. As cyproheptadine by itself did not affect thiopentone sleep and did not antagonize the effect of CPP, the effect of trazodone and CPP seems to be independent of their respective 5-HT-antagonistic and 5-HT-agonistic properties.

The role of trazodone metabolism in its inhibitory action on avoidance response

To assess the role of trazodone metabolism in its depressant action on conditioned avoidance response we investigated whether in the mouse brain 3-chlorophenylpiperazine (CPP) is formed from trazodone, whether trazodone metabolism is affected by a drug metabolism inhibitor, proadifen, and how trazodone, CPP and their combinations act on avoidance responses in proadifen-pretreated mice. It was found that CPP is formed from trazodone in mice, that proadifen inhibits trazodone metabolism, and that the moderate and transient inhibitory effect of trazodone on avoidance responses is dramatically potentiated and prolonged in proadifen-pretreated mice. This effect, and inhibition of unconditioned escape response observed in mice receiving lower doses of trazodone after proadifen pretreatment, were counteracted by CPP. The results indicate that the inhibitory action of trazodone on avoidance response is caused by the parent compound, and that it is brief and moderate because of the rapid metabolism of the drug with formation of CPP which counteracts the depressant effect of the parent compound.

An evaluation of possible interactions between ethanol and trazodone or amitriptyline

The pharmacodynamic effects of single doses of trazodone (100 mg), amitriptyline (50 mg) or placebo either alone or with ethanol (0.5 ml/kg) were investigated in six healthy volunteers in a double-blind crossover study. Plasma concentrations of the drugs and ethanol were also measured. Pharmacodynamic tests were critical flicker fusion frequency threshold (CFF), choice reaction time (CRT), manual dexterity, a digit span test and visual analogue scales. Blood ethanol concentrations were not influenced by the co-administration of either antidepressant. tmax for trazodone was prolonged by ethanol but the other pharmacokinetic parameters for trazodone and amitriptyline were not influenced by ethanol. Trazodone and amitriptyline caused the expected profound depressant effects on CFF, CRT, manual dexterity and on the rating scales for drowsiness, 'clear-headedness', aggression and disinhibition. Ethanol alone impaired manual dexterity, increased drowsiness, reduced 'clear headedness' and also tended to reduce feelings of aggression. In combination with either trazodone or amitriptyline, ethanol caused little additional effect except in the case of manual dexterity which was further impaired. This result may reflect the profound effects of the antidepressants alone and does not suggest that it is safe for patients receiving antidepressant medication to take ethanolic drinks.

Comparative bioavailability of trazodone formulations using stable isotope methodology

The bioavailability of trazodone, a new antidepressant, from 50 mg dividose (A) or film-sealed (B) tablets relative to an oral solution was determined in six healthy male subjects using 50 mg of D4-trazodone as a stable isotope labelled standard. Concentrations of trazodone and D4-trazodone were measured by GCMS. The pharmacokinetics of trazodone and D4-trazodone were identical indicating no isotope effect. For formulation A, B and solution, the relative (trazodone/D4-trazodone) Cmax values were 0.84 +/- 0.09, 0.90 +/- 0.05 and 1.05 +/- 0.04. The relative bioequivalence of the dosage formed with a power of 85% (power by conventional ANOVA was 54%). Among subjects % relative standard deviations (RSD) for the D4-trazodone AUC values, a measure of intra-subject variability, were 6 to 38% while the % RSDs by period, a measure of inter-subject variability, were 26 to 55%.

Plasma levels of trazodone: methodology and applications

A sensitive (to 5.0 ng/ml) and specific method for analysis of the antidepressant trazodone is described. The method utilizes gas-liquid chromatography with nitrogen-phosphorus detection. Applicability of the method is demonstrated by (1) a pharmacokinetic study in a normal volunteer who received 50 mg trazodone orally and (2) steady-state plasma level determinations of 2 patients receiving trazodone in the treatment of depression.

Pharmacokinetic and pharmacodynamic characteristics of trazodone in the elderly

The pharmacokinetic and some pharmacodynamic characteristics of a single oral dose of 100 mg trazodone were compared in young and elderly volunteers. The maximum plasma concentration of trazodone was similar in both age groups. The time to maximum concentration was apparently prolonged in four subjects who swallowed the capsule with a minimal volume of fluid. This may have been due to the capsule being retained in the oesophagus. The terminal phase half-life of trazodone was significantly prolonged (P less than 0.05) and area under the plasma concentration-time curve was significantly larger (P less than 0.01) in the elderly. Apparent oral clearance was significantly reduced (P less than 0.01) in the elderly. Measurement of critical flicker fusion threshold and subjective assessment of alertness using a visual analogue scale, confirmed the sedative effect of trazodone in both age groups. The elderly subjects were less alert for a longer period following drug administration than the young. The differing pharmacokinetic and pharmacodynamic characteristics of trazodone in the young and elderly may be due to an age-related reduction in hepatic drug-metabolising activity, a difference in regional distribution or a change in CNS sensitivity to the drug.

A comparative bioavailability study of Molipaxin capsules and a trazodone liquid formulation in normal volunteers

The pharmacokinetic parameters of Molipaxin capsules and a trazodone liquid formulation have been compared in healthy volunteers. The mean area under the plasma concentration/time curve was 10.07 micrograms h ml-1 and 10.44 micrograms h ml-1, for Molipaxin capsules and trazodone liquid, respectively. The difference was not statistically significant. There was considerable individual variation between the observed maximum plasma concentration of Molipaxin capsules and trazodone liquid but the mean values of 1.61 micrograms/ml and 1.66 micrograms/ml, respectively, were very similar. The time to observed maximum plasma concentrations varied from 15 min to 4 h, but there was no statistical difference between the two formulations. The terminal phase half-life was 7.16 h for Molipaxin capsules and 6.73 h for trazodone liquid. The difference was not statistically significant. Molipaxin capsules and trazodone liquid have similar kinetic profiles and they are considered to have comparable bioavailability. Tolerance to the two formulations was similar.

Effect of dosage and route of administration of trazodone on cerebral concentration of 1-m-chlorophenylpiperazine in rats. Kinetics of trazodone biotransformation in rats

The levels of trazodone (TRZ) and its metabolite, 1-m-chlorophenylpiperazine (CPP) in the rat brain were tested after single and multiple administration of TRZ ip or po. After a single oral dose and after multiple ip or po administration of TRZ, the brain level of CPP exceeded markedly that of the parent compound. Some of pharmacokinetic parameters of TRZ and CPP were significantly changed after chronic treatment. As the biological effect of CPP is opposite to that of its parent compound, the high level of metabolite in the central nervous system may affect strongly the pharmacological activity of TRZ.

[3H]tetrahydrotrazodone binding. Association with serotonin binding sites

High (17 nM) and low (603 nM) affinity binding sites for [3H]tetrahydrotrazodone ([3H] THT), a biologically active analogue of trazodone, have been identified in rat brain membranes. The substrate specificity, concentration, and subcellular and regional distributions of these sites suggest that they may represent a component of the serotonin transmitter system. Pharmacological analysis of [3H]THT binding, coupled with brain lesion and drug treatment experiments, revealed that, unlike other antidepressants, [3H] THT does not attach to either a biogenic amine transporter or serotonin binding sites. Rather, it would appear that [3H]THT may be an antagonist ligand for the serotonin binding site. This probe may prove of value in defining the mechanism of action of trazodone and in further characterizing serotonin receptors.

Trazodone hydrochloride: a wide spectrum antidepressant with a unique pharmacological profile. A review of its neurochemical effects, pharmacology, clinical efficacy, and toxicology

Trazodone is a new antidepressant agent that was recently introduced in the United States. It has a unique pharmacological profile that is not typical of either tricyclic or monoamine oxidase inhibitor antidepressants. As such it represents a new class of antidepressant drugs. The efficacy of trazodone has been clearly established in comparative studies with imipramine and amitriptyline. Major depression is the principal indication for its use, but good results have been shown in a wide variety of depressive subtypes. Of particular importance is the low frequency of adverse reactions seen with this drug.

Antidepressant properties of trazodone

The chemistry, pharmacokinetics, biochemistry and pharmacology, clinical trials, adverse effects, FDA-approved indications, and availability and cost of trazodone hydrochloride, a triazolopyridine antidepressant, are reviewed. Trazodone is nearly completely absorbed after oral administration; although food delays absorption and reduces peak serum concentration, total area under the plasma concentration-time curve is not altered. Trazodone has biphasic elimination, with a redistribution half-life of about one hour and an elimination half-life of 10-12 hours. Trazodone is nearly completely metabolized hepatically by hydroxylation and oxidation to metabolites that are probably inactive. Trazodone is less potent but more selective than conventional tricyclic antidepressants; at low doses, trazodone acts as a serotonin antagonist, while at high doses it acts as a serotonin agonist. Trazodone has been compared with imipramine, amitriptyline, desipramine, and placebo in controlled clinical trials and found to be an effective antidepressant. Trazodone causes significantly fewer anticholinergic side effects than does imipramine. Trazodone has few cardiovascular side effects. In patients ingesting toxic amounts of trazodone, no deaths have been reported unless other drugs were present or ingested concomitantly. The usual adult daily dose of trazodone hydrochloride is 150-400 mg given in two divided doses. Trazodone is an effective antidepressant with a low incidence of serious adverse effects. It may be particularly useful in certain depressed patients who are intolerant of anticholinergic effects of other antidepressants, have cardiac conduction disturbances, or who do not respond to treatment with tricyclic antidepressants and in whom electroshock therapy is contraindicted.

Trazodone (Desyrel, Mead-Johnson Pharmaceutical Division)

Trazodone is the first triazolopyridine derivative to be used clinically for the treatment of depression. It has been shown to be equal in efficacy to the tricyclic antidepressants imipramine, desipramine, and amitriptyline in the treatment of major depressive episodes. Researchers have indicated that trazodone exceeds other antidepressants in relieving anxiety, but further study is needed to confirm this effect. Trazodone has been used successfully to relieve depression in schizophrenic patients without worsening their psychotic symptoms. Trazodone blocks serotonin reuptake into presynaptic neurons with little effect on norepinephrine or dopamine. It is rapidly absorbed orally and reaches peak serum levels within two hours. Trazodone is excreted primarily as metabolites by the kidneys and possesses a biphasic elimination half-life of 4.4 hours for the first 10 hours and 7.5 hours for the next 24 hours. Trazodone 200 mg is equal to imipramine 100 mg, and the therapeutic dosage range is 200-600 mg/d. Side effects are infrequent with trazodone; its anticholinergic activity is minimal. Trazodone appears to produce less cardiovascular toxicity than tricyclic antidepressants. To date, reports of fatal overdoses are rare. Trazodone equals available antidepressant drugs in clinical efficacy, and, because it has fewer cardiovascular and anticholinergic side effects, it should prove beneficial in the treatment of depression.

Pharmacokinetics of trazodone after different routes of administration

Pharmacokinetics study of trazodone after iv, ip and po administration has been performed in rats. Trazodone was given to animals in a single or multiple doses of 20 mg/kg p. o. or ip, or in doses of 5 and 10 mg/kg iv. The levels of the drug in plasma and brain tissue were assayed spectrofluorometrically at predetermined time intervals. The results indicate that neither the route of administration nor the dosage schedule affects in significant manner the pharmacokinetics of trazodone, but the pharmacokinetic parameters depend upon the dose used. The affinity of the drug to blood and brain tissue is nearly the same, in contrast to imipramine which shows, a low affinity to blood and high affinity to brain tissue.

Determination of plasma and brain concentrations of trazodone and its metabolite, 1-m-chlorophenylpiperazine, by gas-liquid chromatography

A sensitive and specific gas chromatographic procedure is described for the quantitation of trazodone and its active metabolite, 1-m-chlorophenylpiperazine (mCPP), in plasma and brain. After addition of internal standards, the samples were extracted with benzene and the extracts divided into two portions. One portion was evaporated to dryness, and residue dissolved in methanol and the solution injected into a gas chromatograph equipped with a nitrogen-selective detector, for trazodone quantitation. To the remaining half of the extracts, 100 microliter of heptafluorobutyric anhydride solution were added and the metabolite was measured as the heptafluorobutyryl derivative by electron-capture detection. Gas chromatography-mass spectrometry was used to confirm the specificity of the analyses. The kinetic profile of trazodone and its metabolite was investigated after oral administration of trazodone (25 mg/kg). The parent drug and its metabolite both accumulated in brain, reaching concentrations several times those in plasma. More mCPP than the parent compound entered the brain; the ratio of the area under the curve for trazodone to mCPP in plasma was about 4, whereas in brain it was only about 0.8.

Trazodone: a review of its pharmacological properties and therapeutic use in depression and anxiety

Trazodone is a triazolopyridine derivative with antidepressant activity, that is chemically unrelated to other currently available antidepressants. Its pharmacological properties differ from those of most other antidepressants. Trazodone exhibits antiserotonin activity in animal studies, but its mechanism of action in depressive illness in humans is not clear. It has an overall therapeutic efficacy comparable with imipramine and amitriptyline in depressive illness but, at dosages which have achieved a similar overall clinical improvement, trazodone causes fewer anticholinergic side effects than the tricyclic antidepressants. Trazodone appears also to have activity against the concomitant anxiety in depressed patients and in limited studies was comparable with diazepam and chlordiazepoxide in anxiety neurosis. Trazodone has been reported to be of value in tremors and chronic alcoholism. Studies in animals, limited human studies and the low incidence of cardiovascular side effects in controlled therapeutic trials, suggest that trazodone is less likely than imipramine to cause cardiotoxicity at therapeutic doses, but the effects of overdosage are not known at present. Trazodone appears to be well tolerated by the elderly, seldom aggravates psychotic symptoms and does not produce neurological side effects.

Trazodone--a new assay procedure and some pharmacokinetic parameters

1 A simple and specific procedure is described for the determination of the new anti-depressant trazodone in human plasma utilising reverse-phase HPLC which is sensitive to 20 ng ml-1. 2 Following oral administration of single 50 mg doses of two formulations of trazodone on separate occasions to healthy fasted volunteers, the peak plasma concentration, time to peak concentration, area under the curve, elimination rate constant and half-life were determined. 3 The two formulations are closely similar and they are considered to have comparable bioavailability.

Central action of mepiprazole

Mepiprazole, a phenylpiperazine derivative, strongly antagonizes the behavioral syndromes evolved by 5-hydroxytrypotophan. The drug did not affect the serotonin neurons in the preparation of flexor reflex of the hind paw of the spinal rat: in higher doses it depressed the reflex showing noradrenolytic properties. Mepiprazole antagonized the fenfluramine-induced hyperthermia, depressed spontaneous locomotor activity, produce hypothermia and was inactive in the despair test. The results suggest that mepiprazol may have noradenolytic properties; its possible influence on the serotonergic system is masked by noradrenolytic properties and hence difficult to demonstrate.

Preliminary study of the biotransformation of two new drugs, trazodone and etoperidone

M-Chlorophenylpiperazine (CPP) is formed in the course of biotransformation of trazodone and etoperidone. The biotransformation of the latter compound is more rapid. An enzymatic inhibitor, proadifen (SKF 525A), inhibited the formation of CPP, while an enzymatic inductor, phenobarbital, did not affect it. The elimination rate of CPP was much lower than that of trazodone; its t0.5 was approx. 50-60 min. The pharmacokinetic data may explain well the pharmacological properties of trazodone and etoperidone.

The interaction of trazodone with rat brain muscarinic cholinoceptors

The muscarinic receptor binding of trazodone, a new nontricyclic antidepressant, was compared with established tricyclic antidepressants. The ability to inhibit the binding of [3H]-quinuclidinyl benzilate in vitro was used for comparing atropine-like effects. Trazodone was found to have essentially no activity at the muscarinic acetylcholine binding site in comparison to the tricyclic antidepressants.