Rat tissue concentrations of chlorimipramine, chlorpromazine and their N-demethylated metabolites after a single oral dose of the parent compounds

Gene Polymorphisms and Drug-Drug Interactions Determine the Metabolic Profile of Blonanserin

This study aimed to evaluate the effects of cytochrome P450 3A4 (CYP3A4) gene polymorphism and drug interaction on the metabolism of blonanserin. Human recombinant CYP3A4 was prepared using the Bac-to-Bac baculovirus expression system. A microsomal enzyme reaction system was established, and drug-drug interactions were evaluated using Sprague-Dawley rats. Ultra-performance liquid chromatography-tandem mass spectrometry was used to detect the concentrations of blonanserin and its metabolite. Compared with wild type CYP34A, the relative clearance of blonanserin by CYP3A4.29 significantly increased to 251.3%, while it decreased notably with CYP3A4.4, 5, 7, 8, 9, 10, 12, 13, 14, 16, 17, 18, 23, 24, 28, 31, 33, and 34, ranging from 6.09% to 63.34%. Among 153 tested drugs, nimodipine, felodipine, and amlodipine were found to potently inhibit the metabolism of blonanserin. Moreover, the inhibitory potency of nimodipine, felodipine, and amlodipine varied with different CYP3A4 variants. The half-maximal inhibitory concentration and enzymatic kinetics assay demonstrated that the metabolism of blonanserin was noncompetitively inhibited by nimodipine in rat liver microsomes and was inhibited in a mixed manner by felodipine and amlodipine in both rat liver microsomes and human liver microsomes. When nimodipine and felodipine were coadministered with blonanserin, the area under the blood concentration-time curve (AUC)(0-t), AUC(0-∞), and C max of blonanserin increased. When amlodipine and blonanserin were combined, the C max of blonanserin C increased remarkably. The vast majority of CYP3A4 variants have a low ability to catalyze blonanserin. With combined administration of nimodipine, felodipine, and amlodipine, the elimination of blonanserin was inhibited. This study provides the basis for individualized clinical use of blonanserin. SIGNIFICANCE STATEMENT: The enzyme kinetics of novel CYP3A4 enzymes for metabolizing blonanserin were investigated. Clearance of blonanserin by CYP3A4.4, 5, 7-10, 12-14, 16-18, 23-24, 28, 31, 33, and 34 decreased notably, but increased with CYP3A4.29. Additionally, we established a drug interaction spectrum for blonanserin, in which nimodipine, felodipine, and amlodipine kinetics exhibited mixed inhibition. Moreover, their inhibitory potencies decreased with CYP3A4.4 and 5 compared to CYP3A4.1. This study provides essential data for personalized clinical use of blonanserin.

Inhibition of the replication of SARS-CoV-2 in human cells by the FDA-approved drug chlorpromazine

INTRODUCTION

Urgent action is needed to fight the ongoing coronavirus disease 2019 (COVID-19) pandemic by reducing the number of infected cases, contagiousness and severity. Chlorpromazine (CPZ), an antipsychotic from the phenothiazine group, is known to inhibit clathrin-mediated endocytosis and has antiviral activity against severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1) and Middle East respiratory syndrome coronavirus. The aim of this in-vitro study was to test CPZ against SARS-CoV-2 in monkey and human cells.

MATERIALS AND METHODS

Monkey VeroE6 cells and human alveolar basal epithelial A549-ACE2 cells were infected with SARS-CoV-2 in the presence of various concentrations of CPZ. Supernatants were harvested at day 2 and analysed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) for the presence of SARS-CoV-2 RNA. Cell viability was assessed in non-infected cells.

RESULTS

CPZ was found to have antiviral activity against SARS-CoV-2 in monkey VeroE6 cells, with a half maximal inhibitory concentration (IC50) of 8.2 µM, half maximal cytotoxic concentration (CC50) of 13.5 µM, and selectivity index (SI) of 1.65. In human A549-ACE2 cells, CPZ was also found to have anti-SARS-CoV-2 activity, with IC50 of 11.3 µM, CC50 of 23.1 µM and SI of 2.04.

DISCUSSION

Although the measured SI values are low, the IC50 values measured in vitro may translate to CPZ dosages used in routine clinical practice because of the high biodistribution of CPZ in lungs and saliva. Also, the distribution of CPZ in brain could be of interest for treating or preventing neurological and psychiatric forms of COVID-19.

CONCLUSIONS

These preclinical findings support clinical investigation of the repurposing of CPZ, a drug with mild side effects, in the treatment of patients with COVID-19.

Repurposing chlorpromazine to treat COVID-19: The reCoVery study

OBJECTIVES

The ongoing COVID-19 pandemic has caused approximately 2,350,000 infections worldwide and killed more than 160,000 individuals. In Sainte-Anne Hospital (GHU PARIS Psychiatrie & Neuroscience, Paris, France) we have observed a lower incidence of symptomatic forms of COVID-19 among patients than among our clinical staff. This observation led us to hypothesize that psychotropic drugs could have a prophylactic action against SARS-CoV-2 and protect patients from the symptomatic and virulent forms of this infection, since several of these psychotropic drugs have documented antiviral properties. Chlorpromazine (CPZ), a phenothiazine derivative, is also known for its antiviral activity via the inhibition of clathrin-mediated endocytosis. Recentin vitro studies have reported that CPZ exhibits anti-MERS-CoV and anti-SARS-CoV-1 activity.

METHODS

In this context, the ReCoVery study aims to repurpose CPZ, a molecule with an excellent tolerance profile and a very high biodistribution in the saliva, lungs and brain. We hypothesize that CPZ could reduce the unfavorable course of COVID-19 infection among patients requiring respiratory support without the need for ICU care, and that it could also reduce the contagiousness of SARS-CoV-2. For this purpose, we plan a pilot, multicenter, randomized, single blind, controlled, phase III therapeutic trial (standard treatment vs. CPZ+standard treatment).

CONCLUSION

This repurposing of CPZ for its anti-SARS-CoV-2 activity could offer an alternative, rapid strategy to alleviate infection severity. This repurposing strategy also avoids numerous developmental and experimental steps, and could save precious time to rapidly establish an anti-COVID-19 therapy with well-known, limited and easily managed side effects.

[Repurposing of chlorpromazine in COVID-19 treatment: the reCoVery study]

OBJECTIVES

The ongoing COVID-19 pandemic comprises a total of more than 2,350,000 cases and 160,000 deaths. The interest in anti-coronavirus drug development has been limited so far and effective methods to prevent or treat coronavirus infections in humans are still lacking. Urgent action is needed to fight this fatal coronavirus infection by reducing the number of infected people along with the infection contagiousness and severity. Since the beginning of the COVID-19 outbreak several weeks ago, we observe in GHU PARIS Psychiatrie & Neurosciences (Sainte-Anne hospital, Paris, France) a lower prevalence of symptomatic and severe forms of COVID-19 infections in psychiatric patients (∼4%) compared to health care professionals (∼14%). Similar observations have been noted in other psychiatric units in France and abroad. Our hypothesis is that psychiatric patients could be protected from severe forms of COVID-19 by their psychotropic treatments. Chlorpromazine (CPZ) is a phenothiazine derivative widely used in clinical routine in the treatment of acute and chronic psychoses. This first antipsychotic medication has been discovered in 1952 by Jean Delay and Pierre Deniker at Sainte-Anne hospital. In addition, to its antipsychotic effects, several in vitro studies have also demonstrated a CPZ antiviral activity via the inhibition of clathrin-mediated endocytosis. Recently, independent studies revealed that CPZ is an anti-MERS-CoV and an anti-SARS-CoV-1 drug. In comparison to other antiviral drugs, the main advantages of CPZ lie in its biodistribution: (i) preclinical and clinical studies have reported a high CPZ concentration in the lungs (20-200 times higher than in plasma), which is critical because of the respiratory tropism of SARS-CoV-2; (ii) CPZ is highly concentrated in saliva (30-100 times higher than in plasma) and could therefore reduce the contagiousness of COVID-19; (iii) CPZ can cross the blood-brain barrier and could therefore prevent the neurological forms of COVID-19.

METHODS

Our hypothesis is that CPZ could decrease the unfavorable evolution of COVID-19 infection in oxygen-requiring patients without the need for intensive care, but also reduce the contagiousness of SARS-CoV-2. At this end, we designed a pilot, phase III, multicenter, single blind, randomized controlled clinical trial. Efficacy of CPZ will be assessed according to clinical, biological and radiological criteria. The main objective is to demonstrate a shorter time to response (TTR) to treatment in the CPZ+standard-of-care (CPZ+SOC) group, compared to the SOC group. Response to treatment is defined by a reduction of at least one level of severity on the WHO-Ordinal Scale for Clinical Improvement (WHO-OSCI). The secondary objectives are to demonstrate in the CPZ+SOC group, compared to the SOC group: (A) superior clinical improvement; (B) a greater decrease in the biological markers of viral attack by SARS-CoV-2 (PCR, viral load); (C) a greater decrease in inflammatory markers (e.g. CRP and lymphopenia); (D) a greater decrease in parenchymal involvement (chest CT) on the seventh day post-randomization; (E) to define the optimal dosage of CPZ and its tolerance; (F) to evaluate the biological parameters of response to treatment, in particular the involvement of inflammatory cytokines. Patient recruitment along with the main and secondary objectives are in line with WHO 2020 COVID-19 guidelines.

CONCLUSION

This repositioning of CPZ as an anti-SARS-CoV-2 drug offers an alternative and rapid strategy to alleviate the virus propagation and the infection severity and lethality. This CPZ repositioning strategy also avoids numerous developmental and experimental steps and can save precious time to rapidly establish an anti-COVID-19 therapy with well-known, limited and easy to manage side effects. Indeed, CPZ is an FDA-approved drug with an excellent tolerance profile, prescribed for around 70 years in psychiatry but also in clinical routine in nausea and vomiting of pregnancy, in advanced cancer and also to treat headaches in various neurological conditions. The broad spectrum of CPZ treatment - including antipsychotic, anxiolytic, antiemetic, antiviral, immunomodulatory effects along with inhibition of clathrin-mediated endocytosis and modulation of blood-brain barrier - is in line with the historical French commercial name for CPZ, i.e. LARGACTIL, chosen as a reference to its "LARGe ACTion" properties. The discovery of those CPZ properties, as for many other molecules in psychiatry, is both the result of serendipity and careful clinical observations. Using this approach, the field of mental illness could provide innovative therapeutic approaches to fight SARS-CoV-2.

The bio-distribution of the antidepressant clomipramine is modulated by chronic stress in mice: effects on behavior

Major depression (MD) is one of the most common psychiatric disorders, severely affecting the quality of life of millions of people worldwide. Despite the availability of several classes of antidepressants, treatment efficacy is still very variable and many patients do not respond to the treatment. Clomipramine (CMI), a classical and widely used antidepressant, shows widespread interindividual variability of efficacy, while the environmental factors contributing to such variability remain unclear. We investigated whether chronic stress modulates the bio-distribution of CMI, and as a result the behavioral response to CMI treatment in a mouse model of chronic social defeat stress (CSDS). Our results show that stress exposure increased anxiety-like and depressive-like behaviors and altered the stress response. Chronic defeat stress furthermore significantly altered CMI bio-distribution. Interestingly, CMI bio-distribution highly correlated with anxiety-like and depressive-like behaviors only under basal conditions. Taken together, we provide first evidence demonstrating that chronic stress exposure modulates CMI bio-distribution and behavioral responses. This may contribute to CMI’s broad interindividual variability, and is especially relevant in clinical practice.

Regional distribution of clomipramine and desmethylclomipramine in rat brain and peripheral organs on chronic clomipramine administration

The tricyclic antidepressant (TCA) clomipramine has been widely used in psychiatry for over 40 years. More recently, its therapeutic potential as an antineoplastic drug has been identified. However, there are no prior data on regional distribution in the brain of clomipramine and its primary metabolite (desmethylclomipramine) after chronic oral administration. The aim of this study was to determine the concentrations of clomipramine and desmethylclomipramine in different rat-brain regions and to compare those with levels in plasma and peripheral organs after chronic oral treatment of Sprague Dawley rats (15 mg/kg) for 14 days. The levels of both parent TCA and metabolite were analysed by high-performance liquid chromatography in six brain regions (cortex, hypothalamus, hippocampus, striatum, brainstem and cerebellum), five peripheral organs and in plasma. Our data show that the cerebral cortex had the highest concentration of clomipramine (2.9 microg/mg), with successively lower concentrations in the hypothalamus, striatum, cerebellum, hippocampus and brainstem. Of the peripheral organs, the lungs and liver, had the highest levels of clomipramine, while in the heart, only the metabolite was detected. The plasma concentration (0.17 microg/ml or 0.48 microM) was comparable to that in the hippocampus and cerebellum (approximately 0.20 microg/mg). The differential distribution of clomipramine in different brain regions and the regional variation in clomipramine to desmethylclomipramine ratios have implications for the use of clomipramine in psychiatry and neuro-oncology.

A comparative proteomics analysis of rat mitochondria from the cerebral cortex and hippocampus in response to antipsychotic medications

An increasing number of experiments have found anomalies in mitochondria in the brains of psychotics, which suggests that mitochondrial dysfunction or abnormal cerebral energy metabolism might play an important role in the pathophysiology of schizophrenia (SCZ). We adopted a proteomic approach to identify the differential effects on the cerebral cortex and hippocampus mitochondrial protein expression of Sprague-Dawley (SD) rats by comparing exposure to typical and atypical antipsychotic medications. Differential mitochondrial protein expressions were assessed using two-dimensional (2D) gel electrophoresis for three groups with Chlorpromazine (CPZ), Clozapine (CLZ), quetiapine (QTP) and a control group. A total of 14 proteins, of which 6 belong to the respiratory electron transport chain (ETC) of oxidative phosphorylation (OXPHOS), showed significant changes in quantity including NADH dehydrogenase (ubiquinone) 1 alpha subcomplex 10 (Ndufa10), NADH dehydrogenase (ubiquinone) flavoprotein 2 (Ndufv2), NADH dehydrogenase (ubiquinone) Fe-S protein 3 (Ndufs3), F1-ATPase beta subunit (Atp5b), ATPase, H+ transporting, lysosomal, beta 56/58 kDa, isoform 2 (Atp6v1b2) and ATPase, H+ transporting, V1 subunit A, isoform 1 (Atp6v1a1). The differential proteins subjected to 2D were assessed for levels of mRNA using quantitative real time PCR (Q-RT-PCR), and we also made partial use of Western blotting for assessing differential expression. The results of our study may help to explain variations in SD rats as well as in human response to antipsychotic drugs. In addition, they should improve our understanding of both the curative effects and side effects of antipsychotics and encourage new directions in SCZ research.

Correlation of plasma and peritoneal diasylate clomipramine concentration with hemodynamic recovery after intralipid infusion in rabbits

OBJECTIVES

Drug sequestration to an expanded plasma lipid phase has been proposed as a potential mechanism of action for lipid emulsions in lipophilic cardiotoxin overdose. The authors set out to document plasma and peritoneal diasylate clomipramine concentration after resuscitation with lipid emulsion in a rabbit model of clomipramine-induced hypotension.

METHODS

Twenty sedated mechanically ventilated New Zealand White rabbits were allocated to receive either 12 mL/kg 20% Intralipid or 12 mL/kg saline solution, following clomipramine infusion to 50% baseline mean arterial pressure (MAP). Hemodynamic parameters and serum clomipramine concentration were determined to 59 minutes. Peritoneal dialysis with 20% Intralipid or saline solution was evaluated for clomipramine concentration.

RESULTS

Mean arterial pressure was greater in lipid-treated animals as assessed by repeated-measures analysis of variance (F[1,14] = 6.84; p = 0.020). Lipid infusion was associated with elevated plasma clomipramine concentration and reduced initial volume of distribution (Vd; 5.7 [+/-1.6] L/kg lipid vs. 15.9 [+/-7.2] L/kg saline; p = 0.0001). Peritoneal diasylate clomipramine concentration was greater in lipid-treated animals (366.2 [+/-186.2] microg/L lipid vs. 37.7 [+/-13.8] microg/L saline; p = 0.002).

CONCLUSIONS

Amelioration of clomipramine-induced hypotension with lipid infusion is associated with reduced initial Vd and elevated plasma clomipramine concentration consistent with intravascular drug-lipid sequestration. Concomitant peritoneal dialysis with lipid emulsion enhances clomipramine extraction.

Chlorpromazine oligomer is a potentially active substance that inhibits human D-amino acid oxidase, product of a susceptibility gene for schizophrenia

D-amino acid oxidase (DAO), a potential risk factor for schizophrenia, has been proposed to be involved in the decreased glutamatergic neurotransmission in schizophrenia. Here we show the inhibitory effect of an antipsychotic drug, chlorpromazine, on human DAO, which is consistent with previous reports using porcine DAO, although human DAO was inhibited to a lesser degree (K(i) = 0.7 mM) than porcine DAO. Since chlorpromazine is known to induce phototoxic or photoallergic reactions and also to be transformed into various metabolites, we examined the effects of white light-irradiated chlorpromazine on the enzymatic activity. Analytical methods including high-resolution mass spectrometry revealed that irradiation triggered the oligomerization of chlorpromazine molecules. The oligomerized chlorpromazine showed a mixed type inhibition with inhibition constants of low micromolar range, indicative of enhanced inhibition. Taken together, these results suggest that oligomerized chlorpromazine could act as an active substance that might contribute to the therapeutic effects of this drug.

Antipsychotic drugs inhibit the function of breast cancer resistance protein

The ABCG2 transporter breast cancer resistance protein (BCRP) has been identified in several physiological sites. It has been suggested to play an important role in disposition of many drugs and environmental toxins. We investigated the effects of several antipsychotic drugs, including risperidone, 9-hydroxy-risperidone (paliperidone), olanzapine, quetiapine, clozapine, haloperidol and chlorpromazine, and a positive control inhibitor Ko143 on functions of BCRP in MCF7 and BCRP over-expressing MCF7/MX100 cell lines using a BCRP prototypical substrate mitoxantrone. Our findings indicated that the tested antipsychotics rank order of potency of inhibition of BCRP according to concentrations required to reach 50% of maximum inhibition (IC(50)) was as follows: Ko143 (0.07 microM) > risperidone (38.1 microM) > clozapine (42.0 microM) > paliperidone (51 microM) > chlorpromazine (52.2 microM) > quetiapine (66.1 microM) > olanzapine = haloperidol (>100.0 microM). We further tested the effects of various concentrations of risperidone on the BCRP-mediated transport of oestrone-3-sulfate in a colon carcinoma cell line, Caco-2, a widely used model to study drug absorption. Our findings show that risperidone at concentrations ranging from 1 to 100 microM significantly inhibited intracellular accumulation of oestrone-3-sulfate in Caco-2 cell monolayers. The present results suggest that a potential source of pharmacokinetic interactions exists between BCRP substrates and several antipsychotics.

CE of tricyclic antidepressant clomipramine and metabolites: Electromigration and wall adsorption

CE of tricyclic antidepressants clomipramine and its metabolites demethylclomipramine, didemethylclomipramine and 8-hydroxyclomipramine resulted in partly extremely tailing peaks in bare fused-silica capillaries. Especially at high pH of the BGE this behavior was not unexpected as adsorption of the cationic analytes onto the negatively charged wall due to electrostatic attraction can be supposed. Less expected was the observation that peak tailing could not be overcome neither by using a capillary with dynamic coating with cationic CTAB added to the BGE, nor by the usage of a capillary permanently coated with polyvinyl alcohol (PVA), both operated at acidic pH. As this tailing was even more pronounced than with bare fused silica, and was suppressed upon addition of MeCN to the BGE, another source of adsorption than pure ion-ion interaction seems plausible. In the bare silica capillary the mobility, mu, of the analytes followed roughly the pH dependence of a monoacidic base, but two deviations from the sigmoid theoretical curve were evident: (i) even at low pH the mobilities were not constant; they decreased in contrary with pH over the entire range; (ii) the apparent pK(a) values of two analytes, derived at the pH with halve the mobility at low pH, are significantly smaller than the thermodynamic pK(a). Upon modifying the expression for mu = f(pH), and considering the pH dependence of the negative charge density at the wall by an additional term which takes chromatographic retention into account, an equation was derived which enables the description of the observed electromigration of the analytes as function of pH, pK(a) of analytes and surface silanol groups, actual mobility of analytes, distribution coefficient (or retention factor) due to adsorption including its pH dependence. The interplay of electrophoretic movement and residual adsorptive retention allowed to resolve the analytes finally in an uncoated capillary, namely at pH 7.65 (30 mM ionic strength), whereas at the cost of the robustness of the separation system.

Evaluation of antipsychotic drugs as inhibitors of multidrug resistance transporter P-glycoprotein

RATIONALE

The multidrug resistance transporter, P-glycoprotein (P-gp), is involved in efflux transport of several antipsychotics in the blood-brain barrier (BBB).

OBJECTIVES

In the present study, we evaluated the inhibitory effect of the antipsychotics, i.e., risperidone, olanzapine, quetiapine, clozapine, haloperidol, chlorpromazine, a major metabolite of risperidone, 9-OH-risperidone, and a positive control inhibitor, PSC833, on the cellular uptake of a prototypic substrate of P-gp, rhodamine (Rhd) 123, in LLC-PK1 and L-MDR1 cells.

MATERIALS AND METHODS

After incubation of the antipsychotics (1-100 microM) and the positive (10 microM PSC833) or negative (1% dimethyl sulfoxide) controls with 5 microM Rhd 123 for 1 h, the effects of the antipsychotics on the intracellular accumulation of Rhd 123 were examined using a flow cytometric method.

RESULTS

All the antipsychotics showed various degrees of inhibitory effects on P-gp activity. The rank order of the concentration of inhibitor to cause 50% of the maximal increment of intracellular Rhd 123 fluorescence (EC(50)) was: PSC833 (0.5 microM) < olanzapine (3.9 microM) < chlorpromazine (5.8 microM) < risperidone (6.6 microM) < haloperidol (9.1 microM) < quetiapine (9.8 microM) < 9-OH-risperidone (12.5 microM) < clozapine (30 microM). Considering that the antipsychotics' plasma concentrations are generally lower than 1 microM, the present results suggest that olanzapine and risperidone are the only agents that may inhibit P-gp activity in the BBB. However, most of the antipsychotics are extensively accumulated in tissues. In addition, when given orally, the drug concentrations in the gastrointestinal tract are likely to be high.

CONCLUSIONS

Pharmacokinetic interactions due to inhibition of P-gp activity by the antipsychotics appear possible and warrant further investigation.

Steady state concentrations of clomipramine and its major metabolite desmethylclomipramine in rat brain and serum after oral administration of clomipramine

Twenty male Sprague-Dawley rats received five oral doses of clomipramine 20 mg/kg at 4-h intervals. The animals were decapitated 1, 2, 3, 5 and 12 h after the last dose for determination of clomipramine and desmethylclomipramine in serum and frontal cerebral cortex. Time dependent concentrations of clomipramine and desmethylclomipramine paralleled in serum and brain. Half-lives were similar in serum and brain with 7.8 versus 6.2 h and 5.5 versus 5.0 h for clomipramine and desmethylclomipramine, respectively. Absolute concentrations, however, were markedly higher in brain than in serum - 12.5 fold for clomipramine and 7.4 fold for desmethylclomipramine. The data indicate that serum and brain concentrations of clomipramine and its demethylated metabolite are rapidly exchanged between blood and brain. Assuming that blood and brain kinetics in man and rat are comparable, it is concluded that monitoring blood concentrations of clomipramine and desmethylclomipramine is a useful way to evaluate brain concentrations.

Increased bioavailability of clomipramine after sublingual administration in rats

This study examined the absorption and disposition of clomipramine in rats after sublingual (5 and 50 mg/kg), oral (50 mg/kg), and iv (5 mg/kg) administration. The mean oral bioavailability of clomipramine was 24.8% and 29.7%, respectively, in conscious rats and in rats anesthetized with ketamine/xylazine (30/3 mg/kg). When given sublingually in isotonic saline at a dose of 50 mg/kg, clomipramine was rapidly absorbed, and the mean absolute bioavailability (36.2%) was increased over oral dosing. The mean AUC values of clomipramine were 2258 +/- 1762 ng.h/mL and 1891 +/- 867 ng.h/mL after oral administration to conscious and anesthetized rats, respectively, and 3303 +/- 1576 ng.h/mL after sublingual administration to anesthetized rats. Sublingual administration (5 mg/kg doses) of clomipramine formulated with a permeation enhancer, 2-hydroxypropyl beta-cyclodextrin, further increased the sublingual bioavailability to 57.1%. The sublingual route may be an alternative route of administration of clomipramine, providing enhanced bioavailability.

N-Dealkylation of chlorimipramine and chlorpromazine by rat liver microsomal cytochrome P450 isoenzymes

The role of different cytochrome P450 isozymes (CYP) in the N-demethylation of chlorimipramine and chlorpromazine has been investigated in liver microsomes from rats by studying the effects of multiple subchronic doses of chlorimipramine, chlorpromazine, phenobarbital and beta-naphthoflavone on the N-demethylation of ethylmorphine, mono-N-demethyl-chlorimipramine and chlorpromazine and on the hydroxylation of aniline. With control microsomes, CYP-dependent metabolism of chlorimipramine and chlorpromazine (100 nmol; 30 min incubation) resulted in the formation of predominantly chlorimipramine (46.5 +/- 4.9 nmol) whereas chlorpromazine (14.1 +/- 0.9 nmol) accounted for only part of the overall metabolism of chlorpromazine. Multiple doses of chlorimipramine increased the capacity of microsomes to N-demethylate ethylmorphine (9.8 +/- 0.73 and 6.08 +/- 0.06 nmol min(-1) (mg protein)(-1) for chlorimipramine-treated and control rats, respectively) as well as itself (4.65 +/- 0.25 and 3.10 +/- 0.33 nmol min(-1) (mg protein)(-1), respectively). Multiple doses of chlorpromazine induced aniline-hydroxylase activity (1.11 +/- 0.16 and 0.94 +/- 0.06 nmol min(-1) (mg protein)(-1) for chlorimipramine and control microsomes, respectively) but the capacity to N-demethylate itself was unchanged. Phenobarbital treatment induced ethylmorphine N-demethylation activity, but did not affect N-demethylation activity, towards chlorimipramine and chlorpromazine. In control microsomes the N-demethylation capacity of chlorimipramine or chlorpromazine (0.160 +/- 0.025 and 0.015 +/- 0.003 nmol min(-1) (mg protein)(-1), respectively) was one order of magnitude lower than that of chlorimipramine or chlorpromazine. The capacity to N-demethylate either chlorimipramine or chlorpromazine was increased by treatment with either phenobarbital or beta-naphthoflavone. In control microsomes, sulphaphenazole markedly inhibited both chlorimipramine-N-mono- and di-N-demethylation, whereas quinidine markedly inhibited the rate of formation of chlorpromazine. The CYP2C and CYP2D subfamilies seem to be involved in the mono N-demethylation of chlorimipramine and chlorpromazine, respectively. Moreover the CYP1A and CYP2B subfamilies might participate in the N-demethylation of either chlorimipramine or chlorpromazine. This could have important implications in the clinical use of chlorimipramine and chlorpromazine in view of the genetic polymorphism of CYP2C and CYP2D isozymes in man.