Effects of trazodone and fluoxetine in the treatment of major depression: therapeutic pharmacokinetic and pharmacodynamic interactions through formation of meta-chlorophenylpiperazine

Solriamfetol and m-chlorophenylpiperazine cause false positive amphetamine results on urine drug screening

Urine drug screening by immunoassay is a common method to quickly identify drug exposures in the emergency setting and to detect unexpected drug exposures in a variety of patient care and occupational health settings. Although they provide rapid results, immunoassays are susceptible to cross-reactivity with other medications and metabolites. Herein we evaluate the performance of the Thermo Scientific DRI Amphetamines immunoassay for reactivity with trazodone, aripiprazole, atomoxetine, solriamfetol and relevant metabolites. Each of these compounds were spiked into drug-free urine across a range of concentrations and assessed for positivity on amphetamine screen. We demonstrate that the Thermo Scientific DRI assay is susceptible to interferences from m-chlorophenylpiperazine (mCPP), the main metabolite of trazodone, and solriamfetol. Characterization of assay-specific interferences in toxicology screening is instrumental for accurate interpretation of toxicology results, evaluation of patients in emergent settings and supporting patient care.

Neurotransmitter, Peptide, and Steroid Hormone Abnormalities in PTSD: Biological Endophenotypes Relevant to Treatment

PURPOSE OF REVIEW

This review summarizes neurotransmitter, peptide, and other neurohormone abnormalities associated with posttraumatic stress disorder (PTSD) and relevant to development of precision medicine therapeutics for PTSD.

RECENT FINDINGS

As the number of molecular abnormalities associated with PTSD across a variety of subpopulations continues to grow, it becomes clear that no single abnormality characterizes all individuals with PTSD. Instead, individually variable points of molecular dysfunction occur within several different stress-responsive systems that interact to produce the clinical PTSD phenotype. Future work should focus on critical interactions among the systems that influence PTSD risk, severity, chronicity, comorbidity, and response to treatment. Effort also should be directed toward development of clinical procedures by which points of molecular dysfunction within these systems can be identified in individual patients. Some molecular abnormalities are more common than others and may serve as subpopulation biological endophenotypes for targeting of currently available and novel treatments.

Pharmacogenetics of trazodone in healthy volunteers: association with pharmacokinetics, pharmacodynamics and safety

Aim: The aim was to evaluate the effect of polymorphisms in metabolizing enzymes and transporters on the pharmacokinetics, pharmacodynamics and adverse effects of trazodone in healthy volunteers. Materials & methods: 36 healthy volunteers receiving a single 100-mg oral dose of trazodone were genotyped for 11 variants in CYP3A4, CYP3A5, CYP2D6 and ABCB1 by real-time PCR. Plasma concentrations were measured using liquid chromatography-tandem mass spectrometry method. Results & conclusion: Sex affected the pharmacokinetics of trazodone with higher clearance in women. Polymorphisms in ABCB1, but not in CYP3A or CYP2D6, influenced trazodone pharmacokinetics. Trazodone decreased blood pressure and prolonged the corrected QT interval interval. CYP2D6 and ABCB1 polymorphisms were associated with the incidence of dizziness and prolonged corrected QT interval, respectively. Subjects with adverse drug reactions had lower concentrations of trazodone suggesting its metabolite (m-chlorophenylpiperazine) could be responsible for these effects.

Trazodone Addition to Paroxetine and Mirtazapine in a Patient with Treatment-Resistant Depression: The Pros and Cons of Combining Three Antidepressants

Dual antidepressant combination for treatment-resistant depression is a strategy well supported by literature and accepted in clinical practice. Rather, the usefulness of the combination of more than two antidepressants is controversial. This may be related to the possibility of higher side-effect burden and to doubts about its pharmacological effectiveness and therapeutic advantage compared to other standard treatment options. We report a relapse of moderate-to-severe depressive symptoms with insomnia that successfully remitted after the addition of trazodone to a dual combination of paroxetine and mirtazapine (in standard effective doses) in a patient with treatment-resistant depression. We also review the literature and discuss the utility of triple antidepressant combination in treatment-resistant depression. This clinical case highlights the utility of combining trazodone as a third antidepressant for the relapse of depressive symptoms after the failure of a dual antidepressant combination. Trazodone may be advantageous in patients presenting recurrence of moderate-to-severe depressive symptoms that include sleep problems and/or insomnia and may be particularly useful when benzodiazepines are not recommended. Although its use may be controversial and associated with higher risk of side-effects, more investigation is needed to determine the efficacy and safety for triple antidepressant combinations as reliable strategies for treatment-resistant depression in clinical practice.

Antidepressant Drug Interactions

Second-generation antidepressants are more selective in their pharmacological mechanisms and offer fewer side effects and a safer toxicological profile than cyclic antidepressants and monoamine oxidase inhibitors. While the risk for pharmacodynamic interactions is more limited than with older agents with broader receptor effects, the risks for pharmacokinetic interactions is greater. The capacity of selective serotonin reuptake inhibitors to inhibit the metabolic activity of cytochrome P450 isozyme system has spurred over a decade of intense psychopharmacological and pharmacogenetics research to better the understanding of the significance of these interactions. Clinicians have had to increase their knowledge and understanding of drug interaction potential to better manage patients receiving these newer antidepressants. The following is a review of both pharmacodynamic and pharmacokinetic drug-drug interactions with antidepressants.

Relations of depressive symptoms and antidepressant use to body mass index and selected biomarkers for diabetes and cardiovascular disease

OBJECTIVES

We investigated whether depressive symptoms and antidepressant use are associated with biomarkers for glucose dysregulation and inflammation, body mass index (BMI), and waist circumference.

METHODS

Postmenopausal women were recruited into the Women's Health Initiative from 1993 to 1998, and data were collected at regular intervals through 2005. We used multiple linear regression models to examine whether depressive symptoms and antidepressant use are associated with BMI, waist circumference, and biomarkers.

RESULTS

Analysis of data from 71, 809 women who completed all relevant baseline and year 3 assessments showed that both elevated depressive symptoms and antidepressant use were significantly associated with higher BMI and waist circumference. Among 1950 women, elevated depressive symptoms were significantly associated with increased insulin levels and measures of insulin resistance. Analyses of baseline data from 2242 women showed that both elevated depressive symptoms and antidepressant use were associated with higher C-reactive protein levels.

CONCLUSIONS

Monitoring body habitus and other biomarkers among women with elevated depression symptoms or taking antidepressant medication may be prudent to prevent diabetes and cardiovascular disease.

Adjunctive sleep medications and depression outcome in the treatment of serotonin-selective reuptake inhibitor resistant depression in adolescents study

OBJECTIVE

In the Treatment of Resistant Depression in Adolescents, study participants who received medication for sleep had a lower response rate. This report sought to clarify this finding.

METHOD

Depressed adolescents who had not responded to a previous adequate serotonin-selective reuptake inhibitor (SSRI) trial were randomly assigned to another SSRI, venlafaxine, another SSRI+cognitive behavior therapy (CBT), or venlafaxine+CBT. Augmentation with sleep medication was permitted as clinically indicated.

RESULTS

Youth who received trazodone were six times less likely to respond than those with no sleep medication (adjusted odds ratio [OR]=0.16, 95% confidence interval [CI]: 0.05-0.50, p=0.001) and were three times more likely to experience self-harm (OR=3.0, 95% CI: 1.1-7.9, p=0.03), even after adjusting for baseline differences associated with trazodone use. None (0/13) of those cotreated with trazodone and either paroxetine or fluoxetine responded. In contrast, those treated with other sleep medications had similar rates of response (60.0% vs. 50.4%, χ(2)=0.85, p=0.36) and of self-harm events (OR=0.5, 95% CI: 0.1-2.6, p=0.53) as those who received no sleep medication.

CONCLUSIONS

These findings should be interpreted cautiously because these sleep agents were not assigned randomly, but at clinician discretion. Nevertheless, they suggest that the use of trazodone for the management of sleep difficulties in adolescent depression should be re-evaluated and that future research on the management of sleep disturbance in adolescent depression is needed. The very low response rate of participants cotreated with trazodone and either fluoxetine or paroxetine could be due to inhibition of CYP 2D6 by these antidepressants.

Serum zinc level in depressed patients during zinc supplementation of imipramine treatment

BACKGROUND

Recurrent major depression is associated with decreased blood zinc concentrations that may be increased by effective antidepressant therapy. Some clinical investigations point to alterations of the zinc level in blood as a potential marker of depression.

METHODS

A placebo-controlled, double blind study of zinc supplementation to imipramine therapy was conducted on sixty patients fulfilling the DSM-IV criteria for major depression (18-55 years old, 40 females, 20 males). Moreover, a group of 25 healthy volunteers was recruited (16 females, 9 males). Blood samples were drawn for the assay of serum zinc once from the control subjects and four times (before, and then 2, 6 and 12 weeks after the beginning of treatment) from the depressed subjects.

RESULTS

We report that: 1) the serum zinc level was significantly lower (by 22%) in depressed patients than in healthy volunteers, 2) all groups demonstrated a gradual increase in zinc concentrations over the period of imipramine treatment with or without zinc supplementation, 3) treatment-resistant patients demonstrated lower concentrations of zinc (by 14%) than treatment-non-resistant patients, 4) zinc concentrations were higher in zinc-supplemented patients than in placebo-supplemented patients, 5) zinc supplementation increased zinc concentrations over the period of treatment, and 6) at a 12-week imipramine treatment, a significant negative correlation was demonstrated between the Montgomery-Asberg Depression Rating Scale and the serum zinc level together with a concomitant increase in serum zinc in patients in remission.

CONCLUSIONS

Serum zinc is a state marker of depression.

Structure, function, regulation and polymorphism and the clinical significance of human cytochrome P450 1A2

Human CYP1A2 is one of the major CYPs in human liver and metabolizes a number of clinical drugs (e.g., clozapine, tacrine, tizanidine, and theophylline; n > 110), a number of procarcinogens (e.g., benzo[a]pyrene and aromatic amines), and several important endogenous compounds (e.g., steroids). CYP1A2 is subject to reversible and/or irreversible inhibition by a number of drugs, natural substances, and other compounds. The CYP1A gene cluster has been mapped on to chromosome 15q24.1, with close link between CYP1A1 and 1A2 sharing a common 5'-flanking region. The human CYP1A2 gene spans almost 7.8 kb comprising seven exons and six introns and codes a 515-residue protein with a molecular mass of 58,294 Da. The recently resolved CYP1A2 structure has a relatively compact, planar active site cavity that is highly adapted for the size and shape of its substrates. The architecture of the active site of 1A2 is characterized by multiple residues on helices F and I that constitutes two parallel substrate binding platforms on either side of the cavity. A large interindividual variability in the expression and activity of CYP1A2 has been observed, which is largely caused by genetic, epigenetic and environmental factors (e.g., smoking). CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR) and CYP1A2 is induced through AhR-mediated transactivation following ligand binding and nuclear translocation. Induction or inhibition of CYP1A2 may provide partial explanation for some clinical drug interactions. To date, more than 15 variant alleles and a series of subvariants of the CYP1A2 gene have been identified and some of them have been associated with altered drug clearance and response and disease susceptibility. Further studies are warranted to explore the clinical and toxicological significance of altered CYP1A2 expression and activity caused by genetic, epigenetic, and environmental factors.

Mechanism of action of trazodone: a multifunctional drug

Multifunctional drugs are those with more than one therapeutic mechanism. Trazodone is a multifunctional drug with dose-dependent pharmacologic actions. That is, it has hypnotic actions at low doses due to blockade of 5-HT2Areceptors, as well as H1histamine receptors and α1 adrenergic receptors. Higher doses recruit the blockade of the serotonin transporter (SERT) and turn trazodone into an antidepressant. Although trazodone has traditionally been used as a low dose hypnotic, a new controlled release formulation that has the potential to improve the tolerability of high doses may provide an opportunity to revisit this multifunctional drug as an antidepressant as well.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Proof of a 1-(3-chlorophenyl)piperazine (mCPP) intake—Use as adulterant of cocaine resulting in drug–drug interactions?

Since 2005, increasing numbers of seizures of the designer drug of abuse 1-(3-chlorophenyl)piperazine (mCPP) have been reported. This paper describes the unequivocal proof of a mCPP intake. Differentiation from the intake of its precursor drugs trazodone and nefazodone was performed by a systematic toxicological analysis (STA) procedure using full-scan GC-MS after acid hydrolysis, liquid-liquid extraction and microwave-assisted acetylation. The found mCPP/hydroxy-mCPP ratio indicated altered metabolism of this cytochrome (CYP) 2D6 catalyzed reaction compared to published studies using the same procedure. Although this might be ascribed to a poor metabolizer (PM) phenotype, genotyping revealed no PM genotype but indications for an intermediate metabolizer genotype. However, a PM phenotype could also be caused by drug-drug interactions with CYP2D6 inhibitors or substrates such as the co-consumed cocaine and diltiazem and/or diltiazem metabolites, respectively. In conclusion, the presented data indicate a possible relevance of CYP2D6 polymorphism and/or drug interactions to mCPP toxicokinetics, which is important for risk assessment of this new designer drug of abuse, in particular if it is used as adulterant of CYP2D6 substrates such as cocaine.

Trazodone and ejaculatory inhibition

Sexual adverse effects are common with psychotropics. Rational polypharmacy may confound etiology. This case report describes development of ejaculatory inhibition in a male patient with co-morbid psychiatric diagnoses treated with fluoxetine, divalproex sodium, lamotrigine, trazodone, and clonazepam. Detailed psychotropic history with time-line of adverse effect onset implicated trazodone. Within 48 hours of trazodone discontinuation, ejaculatory inhibition was resolved. Clinicians should be aware that trazodone may cause ejaculatory inhibition, understand that determination of sexual adverse effects necessitates directed and periodic questioning as these symptoms may increase in severity over time, and appreciate that religious patients may find discussing this issue difficult.

Does trazodone have a role in palliating symptoms?

INTRODUCTION

Trazodone is a unique antidepressant, which blocks the postsynaptic serotonin (5-HT) receptors, 5-HT(2A) and 5-HT(2C), and weakly inhibits presynaptic 5-HT transporters.

DISCUSSION

Trazodone is well-absorbed by the mouth and is metabolized by three cytochromes: CYP1A2, CYP2D6, and CYP3A4. Clinical benefits include reduced insomnia in those depressed and/or on antidepressants. Pain may be relieved by mechanisms similar to venlafaxine. Delirium unresponsive to neuroleptics has been reported to respond to trazodone. Drug interactions are a risk due to cytochrome metabolism.

CONCLUSION

Trazodone has a unique pharmacology, which may be an advantage in palliating symptoms; however, little evidence is available through cohort or randomized trials to give guidance to its use.

La métachlorophénylpipérazine (mCPP) : une nouvelle drogue de synthèse

Metachlorophenylpiperazine (mCPP) is a psychoactive substance that appeared in 2004 on the black market of illicit substances in Europe and France. It has a strong affinity for serotoninergic receptors and the serotonin transporter. In humans, mCPP induces endocrine, neurological and psychiatric effects. Its subjective effects are similar to those of amphetamines. However, drug-users allot few positive subjective effects. Reported cases of intoxication are generally not serious but the risks of psychiatric disorders and serotoninergic syndrome must be taken into account. Risk factors of the intoxication to mCPP are the existence of predisposing psychiatric pathologies and pharmacodynamic or metabolic interactions. mCPP does not exhibit reinforcing effects. mCPP is not the subject of any international regulation: procedures of medical and social risk assessment were implemented in European and the national levels.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Does meta-chlorophenylpiperazine (mCPP) activate human platelets?

mCPP (meta-chlorophenylpiperazine), an agonist at serotonin (5-hydroxytryptamine, 5-HT) 5-HT2 receptors, has been used as a probe of serotonergic function. We assessed its effect on platelet activation by measuring median platelet volume (MPV), the Sonoclot (SCT) pattern and plasma and intraplatelet serotonin. (a) In vitro study: MPV was measured (n = 7) using a high-resolution channelyzer: Saline (median and range (5.23 fl; 5.10-6.18) vs. mCPP (5.36; 5.10-6.44) P = 0.03; ADP (5.42; 5.29-6.44) vs. ADP + mCPP (5.67; 5.42-6.63) P = 0.02; mCPP (5.36; 5.10-6.44) vs. ADP + mCPP (5.67; 5.42-6.63) P = 0.02. Therefore, mCPP increases the MPV and enhances the effect of ADP. (b) In vivo study: The SCT time to inflection (TI) and time to peak (TP) were measured following the oral administration of mCPP (0.5 mg/kg) or aspirin (300 mg) (n = 10). Ingestion of mCPP significantly shortened TI and TP indicating platelet activation. TI: 0 h (mean +/- SD: 10.2 +/- 2.0 min) vs. 6 h (9.3 +/- 1.5) P = 0.03; TP: 0 h (31.9 +/- 7.6) vs. 6 h (23.1 +/- 2.9) P = 0.01. Aspirin had no effect on TI or TP. There were no significant changes in plasma and intraplatelet 5-HT. It is concluded that mCPP activates human platelets via 5-HT receptors.

Serotonin 5-HT2C receptors as a target for the treatment of depressive and anxious states: focus on novel therapeutic strategies

Serotonin (5-HT)2C receptors play an important role in the modulation of monoaminergic transmission, mood, motor behaviour, appetite and endocrine secretion, and alterations in their functional status have been detected in anxiodepressive states. Further, 5-HT2C sites are involved in the actions of several classes of antidepressant. At the onset of treatment, indirect activation of 5-HT2C receptors participates in the anxiogenic effects of selective 5-HT reuptake inhibitors (SSRIs) as well as their inhibition of sleep, sexual behaviour and appetite. Conversely, progressive down-regulation of 5-HT2C receptors parallels the gradual onset of clinical efficacy of SSRIs. Other antidepressants, such as nefazodone or mirtazapine, act as direct antagonists of 5-HT2C receptors. These observations underpin interest in 5-HT2C receptor blockade as a strategy for treating depressive and anxious states. This notion is supported by findings that 5-HT2C receptor antagonists stimulate dopaminergic and adrenergic pathways, exert antidepressant and anxiolytic actions in behavioural paradigms, and favour sleep and sexual function. In addition to selective antagonists, novel strategies for exploitation of 5-HT2C receptors embrace inverse agonists, allosteric modulators, ligands of homo/heterodimers, modulators of interactions with 'postsynaptic proteins', dual melatonin agonists/5-HT2C receptor antagonists and mixed 5-HT2C/alpha2-adrenergic antagonists. Intriguingly, there is evidence that stimulation of regionally discrete populations of 5-HT2C receptors is effective in certain behavioural models of antidepressant activity, and promotes neurogenesis in the hippocampus. This article explains how these ostensibly paradoxical actions of 5-HT2C antagonists and agonists can be reconciled and discusses both established and innovative strategies for the exploitation of 5-HT2C receptors in the improved management of depressed and anxious states.

Confirmation of the neurophysiologically predicted therapeutic effects of trazodone on its target symptoms depression, anxiety and insomnia by postmarketing clinical studies with a controlled-release formulation in depressed outpatients

Early human pharmaco-EEG and subsequent sleep laboratory studies identified trazodone, a 5-HT(2) antagonist and 5-HT reuptake inhibitor (SARI), as an antidepressant with therapeutic effects on its target symptoms depressed mood, anxiety and insomnia. On the occasion of the introduction of a controlled-release (CR) formulation (Trittico 150 mg retard, marketed in Austria by CSC Pharmaceuticals Handels GmbH, Vienna, Austria) in Austria in July 2000, a multi-center, open, clinical post-marketing study on the therapeutic effects, safety and target symptoms of trazodone CR in depression was carried out at 80 offices of Austrian neuropsychiatrists. 549 outpatients (63% females) of all age groups suffering from five different subtypes of depression were enrolled in the study. After a 2-week fixed dose-titration regimen up to 150 mg and a 4-week adjustment period to the optimum dose, 66% of the patients remained on 150 mg, 20% increased the dose and 11% decreased it. Only 3.7% discontinued treatment. Rating by the neuropsychiatrists based on the Clinical Global Impression showed very much to much improvement in 78.3% of the patients, and no change or a deterioration in only 3.6%. In the Hamilton Depression Scale (HAMD) a statistically significant improvement from a baseline score of 21 to a score of 14 after 2 weeks was found, and a normalization to a score of 8 after 6 weeks. Therapeutic effects were similar in the five groups suffering from different subtypes of depression and in patients with and without comedication. Self-rating by the patients based on the Zung Self-Rating Depression Scale (SDS) and Zung Self-Rating Anxiety Scale (SAS) also showed a significant improvement in the 2nd and 6th week of therapy. Evaluation of the target symptoms of trazodone by ranking the most improved symptoms identified insomnia as the most improved psychopathological item in all three scales. While in the observer ratings also suicidal tendencies and weight loss were found much improved, in the self-rated Zung SDS sadness and loss of drive came second and third in the improvement ranking, in the self-rated Zung SAS anxiety and the feeling of falling apart. Tolerability was very good. In the 2nd week only 16.9% and in the 6th week only 7.6% of the patients reported side effects, mostly characterized by tiredness and rarely by nausea and vertigo. The present clinical study is in agreement with previous studies identifying trazodone as a safe and effective antidepressant, specifically regarding its target symptoms insomnia, depression and anxiety. It also confirms our own early predictions based on neurophysiological investigations concerning the mode of action of the drug.

Anti-Hypertension Effect of Vanylidilol: A Phenylaldehyde α/β-Adrenoceptor Blocker with Endothelium-Dependent and K+ Channels Opening-Associated Vasorelaxant Activities

The antihypertensive effect of vanylidilol, a new alpha/beta-adrenoceptor antagonist with endothelium-dependent and K(+)-channel-opening activities, was investigated in normotensive and hypertensive Wistar rats. Vanylidilol competitively antagonized (-)isoproterenol-induced positive chronotropic effects, inotropic effects, and tracheal relaxation effects in isolated rat right atria, left atria, and guinea pig tracheal strips in a concentration-dependent manner. Vanylidilol's apparent pA(2) values were 6.36 +/- 0.08 (right atria), 6.41 +/- 0.07 (left atria), and 6.31 +/- 0.06 (trachea). Vanylidilol also produced a competitive antagonism of phenylephrine-induced contraction in the isolated rat aorta with pA(2) values of 6.79 +/- 0.18. In the radioligand binding assay, vanylidilol inhibited [(3)H]CGP-12177 binding to rat ventricle and lung tissues and [(3)H]prazosin binding to brain membranes with Ki values of 535.17, 2,066.69, and 431.11, respectively. In isolated rat thoracic aorta, vanylidilol's vasorelaxant effects on phenylephrine (10 micromol/l)-induced contractions were attenuated by removing endothelium and by the presence of L-N(G)-nitro arginine methyl ester (L-NAME; 100 micromol/l), methylene blue (10 micromol/l), 1H-[1,2,4]oxadiazolol[4,3,-a] quinoxalin-1-one (ODQ; 10 micromol/l), tetraethylammonium (10 mmol/l), glibenclamide (1 micromol/l), apamin (1 micromol/l), and charybdotoxin (0.1 micromol/l). In addition, vanylidilol, in an equally antagonistic activity, inhibited phenylephrine-induced phasic and tonic contractions. Intravenous vanylidilol further reduced mean blood pressure in pentobarbital-anesthetized normotensive Wistar rats in a dose-dependent manner. The oral administration of vanylidilol to conscious spontaneously hypertensive rats had a long-lasting hypotensive effect on the heart rate and decreased it in a dose-dependent manner. Furthermore, vanylidilol's vasodilator effect can be attributed in part to the release of NO or NO-related substance from vascular endothelium, while the endothelium-independent mechanism involved in vanylidilol's relaxation is probably linked to the activation of the K(+) channels and the alpha-adrenoceptor blocking activity in these vessels.

Metabolic drug interactions with new psychotropic agents

New psychotropic drugs introduced in clinical practice in recent years include new antidepressants, such as selective serotonin reuptake inhibitors (SSRI) and 'third generation' antidepressants, and atypical antipsychotics, i.e. clozapine, risperidone, olanzapine, quetiapine, ziprasidone and amisulpride. These agents are extensively metabolized in the liver by cytochrome P450 (CYP) enzymes and are therefore susceptible to metabolically based drug interactions with other psychotropic medications or with compounds used for the treatment of concomitant somatic illnesses. New antidepressants differ in their potential for metabolic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, while nefazodone is a potent inhibitor of CYP3A4. These antidepressants may be involved in clinically significant interactions when coadministered with substrates of these isoforms, especially those with a narrow therapeutic index. Other new antidepressants including sertraline, citalopram, venlafaxine, mirtazapine and reboxetine are weak in vitro inhibitors of the different CYP isoforms and appear to have less propensity for important metabolic interactions. The new atypical antipsychotics do not affect significantly the activity of CYP isoenzymes and are not expected to impair the elimination of other medications. Conversely, coadministration of inhibitors or inducers of the CYP isoenzymes involved in metabolism of the various antipsychotic compounds may alter their plasma concentrations, possibly leading to clinically significant effects. The potential for metabolically based drug interactions of any new psychotropic agent may be anticipated on the basis of knowledge about the CYP enzymes responsible for its metabolism and about its effect on the activity of these enzymes. This information is essential for rational prescribing and may guide selection of an appropriate compound which is less likely to interact with already taken medication(s).

Short-term exposure to low-dose ritonavir impairs clearance and enhances adverse effects of trazodone

Antiretroviral agents may participate in drug interactions that influence the efficacy and toxicity of other antiretrovirals, as well as pharmacologic treatments of coincident or complicating diseases. The viral protease inhibitor, ritonavir, may cause drug interactions by inhibiting the activity of cytochrome P450-3A (CYP3A) isoforms. In a single-dose, blinded, four-way crossover study, 10 healthy volunteer subjects received 50 mg of trazodone hydrochloride or matching placebo concurrent with low-dose ritonavir (four doses of 200 mg each) or with placebo. Compared to the control condition, ritonavir significantly reduced apparent oral clearance of trazodone (155 +/- 23 vs. 75 +/- 12 ml/min, p < 0.001), prolonged elimination half-life (6.7 +/- 0.7 vs. 14.9 +/- 3.9 h, p < 0.05), and increased peak plasma concentrations (842 +/- 64 vs. 1125 +/- 111 ng/ml, p < 0.05) (mean +/- SE). Coadministration of trazodone with ritonavir increased sedation, fatigue, and performance impairment compared to trazodone plus placebo; differences reached significance only for the digitsymbol substitution test. Three subjects experienced nausea, dizziness, or hypotension when trazodone was given with ritonavir; 1 of these subjects also experienced syncope. Thus short-term low-dose administration of ritonavir impairs oral clearance of trazodone and increases the occurrence of adverse reactions. The findings are consistent with impairment of CYP3A-mediated trazodone metabolism by ritonavir.

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.

Psychomotor slowing, neuroendocrine responses, and behavioral changes after oral administration of meta-chlorophenylpiperazine in normal volunteers

The mixed 5-HT receptor agonist/antagonist meta-chlorophenylpiperazine (mCPP) is known to suppress locomotor activity in mice and rats. This study aimed: (1) to determine whether mCPP induces cognitive and motor changes in normal human volunteers and how these changes relate to the neuroendocrine effects of mCPP; and (2) to compare these cognitive and motor changes to the known cognitive and motor slowing patterns in depression and schizophrenia. A computerized method (used in previous research) analyzed fine motor behavior during figure-copying tasks. In 14 normal male volunteers behavioral responses, body temperature, plasma levels of prolactin and cortisol, and cognitive and motor performance during figure-copying tasks were measured after a single oral dose of mCPP (0.5 mg/kg). mCPP-induced prolongation of the reaction times in all copying tasks, parallel to increases in cortisol and prolactin and some self-reported behavioral effects. There were no changes in the movement times or the velocities of the writing movements. In conclusion, mCPP induced cognitive, but not motor slowing, in normal male volunteers. This indicates that the human serotonin system is also implicated in psychomotor behavior. This pattern of slowing was different from that in depressed and schizophrenic patients.

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.

Mapping of brain activation in response to pharmacological agents using fMRI in the rat

Functional MRI (fMRI) was used to investigate the effects of psychotropic compound activity in the rat brain in vivo. The effects of dizocilpine (MK-801) an N-methyl-D-aspartate receptor antagonist and m-chlorophenylpiperazine (mCPP), a 5-HT(2b/2c)-receptor agonist on rat brain activity were investigated over a time interval of about 1 h and the results were compared to published glucose utilisation and cerebral blood flow data. Signal magnitude increases were observed predominantly in limbic regions following MK-801 administration (0.5 mg/kg i.v) whereas signal decreases were restricted to neocortical areas; a characteristic, time dependent pattern of regional changes evolved from the thalamic nuclei to cortical regions. In contrast, mCPP (25 mg/kg i.p) produced gradual signal intensity increases in limbic and motor regions with signal decreases restricted to the visual, parietal and motor cortices. The results from both compounds show remarkable similarity with autoradiographic measurements of cerebral blood flow and glucose uptake. These experiments suggest that the spatio-temporal capabilities of fMRI may be applied to the in vivo investigation of psychoactive compound activity with potential for clinical applications.

Metabolism of some "second"- and "fourth"-generation antidepressants: iprindole, viloxazine, bupropion, mianserin, maprotiline, trazodone, nefazodone, and venlafaxine

1. This review summarizes the major known aspects of the metabolism of second-generation (iprindole, viloxazine, bupropion, mianserin, maprotiline, and trazodone) and fourth-generation (nefazodone and venlafaxine) antidepressants. 2. Discussions about specific enzymes involved and about possible pharmacokinetic drug-drug interactions, particularly as they relate to cytochrome P450 enzymes, are provided.

Debate resolved: there are differential effects of serotonin selective reuptake inhibitors on cytochrome P450 enzymes

In 1993, it was first proposed that an important difference between selective serotonin reuptake inhibitors (SSRIs) was the degree of inhibition of the cytochrome P450 (CYP) enzyme 2D6 that they produced under usually dosing conditions (Preskorn, 1993). Specifically, fluoxetine and paroxetine, in contrast to sertraline, were identified as causing substantial increases in the plasma levels of coadministered drugs, which were principally dependent on CYP 2D6 for their metabolism. Over the next 5 years, this position was hotly contested (Preskorn and Nemeroff, 1997). However, an extensive body of research has now accumulated, which incontrovertibly supports the original position. This paper will reviews this research and extends the discussion to all five SSRIs and four other important CYP enzymes: 1A2, 2C9/10, 2C19, and 3A3/4.