Comparative effects of selected phenothiazine tranquilizers and antihistaminics on bacterial cells and possible interactions with antibiotics

Evaluation of the antibacterial effect of phenothiazine antihistaminics (trimeprazine, promethazine, and fonazine) and phenothiazine tranquilizers (promazine, chlorpromazine, triflupromazine, and propiomazine) on Staphylococcus aureus showed that tranquilizers were more active [minimum inhibitory concentration (MIC) 0.5-1.6 micrograms/mL] than antihistaminics (MIC greater than 1.6 micrograms/mL). The antibacterial activity was found to correlate with both the rate of adsorption of these drugs on the bacterial cells and the surface tension of their solutions. Phenothiazine tranquilizers caused rapid and extensive leakage of potassium ions from bacterial cells, while phenothiazine antihistaminics produced relatively slower leakage of these ions. A study of the effect of the phenothiazines on the antibacterial activity of some antibiotics showed that all phenothiazines produced a synergistic effect with erythromycin and an antagonistic effect with tobramycin. Variable effects were observed with chloramphenicol, and no effect was observed with penicillin. Results were explained on the basis of structural characteristics of the phenothiazines.     

The broad-spectrum antimycobacterial activities of phenothiazines, InVitro: somewhere in all of this there may be patentable potentials

The phenothiazines are neuroleptic drugs that have long been known to have antimycobacterial activity, in vitro. Of the various commercially available phenothiazines, thioridazine, chlorpromazine and trifluoperazine are most active against mycobacteria, in vitro. Their MICs for Mycobacterium tuberculosis are in the 8-16 μg/ml range and MICs for Mycobacterium avium in the 10-32 μg/ml range, depending on methods and media. These concentrations cannot be safely attained in humans, where maximum serum concentrations are 0.5 μg/ml (thioridazine) to 1 μg/ml (chlorpromazine) or 4 μg/ml (trifluoperazine). Phenothiazines still have potential as antimycobacterial drugs because they accumulate in macrophages; concentrations inside macrophages are at least 10 fold higher than in serum. When applied to mycobacteria inside macrophages, concentrations as low as 0.1 μg/ml (thioridazine) or 0.1-3.6 μg/ml (chlorpromazine) kill phagocytized M. tuberculosis and M. avium in 3-7 days. Owing to their multiple and novel drug targets, phenothiazine resistance has not been observed. The drug targets and less toxic phenothiazine derivatives (patents include WO2005105145A and WO2010122012A) provide excellent patentable potentials. Thioridazine itself may be patented as "new use". New drugs for treatment of mycobacterial disease, most notable multidrug- and extensively drug-resistant tuberculosis, are urgently needed; phenothiazines and their targets should be exploited for this use.     

Inhibition of circling behavior by neuroleptic drugs in mice with unilateral 6-hydroxydopamine lesions of the striatum

The development of circling behavior to apomorphine, amphetamine and l-Dopa in mice with unilateral 6-hydroxydopamine lesions of the dopaminergic nerve terminals in the striatum has been studied, and the effect of a range of neuroleptic and sedative drugs on this circling behaviour has been investigated. Circling induced by all the stimulant drugs was inhibited in a dose-dependent manner by haloperidol, pimozide, chlorpromazine, metoclopramide and clozapine (in descending rank order of potency), but not by phenoxybenzamine, diazepam, promethazine and pentobarbitone sodium. This relatively simple animal model appears useful for screening neuroleptic drugs which may block striatal dopamine receptors, thereby predicting their potency to cause unwanted extrapyramidal effects but not their antipsychotic efficacy.     

Interactions between neuroleptics and CYP2C6 in rat liver--in vitro and ex vivo study

The aim of the present study was to investigate the influence of classic and atypical neuroleptics on the activity of rat CYP2C6 measured as a rate of warfarin 7-hydroxylation. The reaction was studied in control liver microsomes in the presence of neuroleptics, as well as in microsomes of rats treated intraperitoneally for one day or two weeks (twice a day) with pharmacological doses (mg/kg) of the drugs (promazine, levomepromazine, thioridazine, perazine 10, chlorpromazine, haloperidol 0.3, risperidone 0.1, sertindole 0.05), in the absence of the neuroleptics in vitro. Some of the neuroleptics added in vitro to control liver microsomes decreased the activity of CYP2C6. Sertindole and levomepromazine (Ki = 25 and 31 microM, respectively) were the most potent inhibitors of the rat CYP2C6 among the drugs studied. Their effects were more pronounced than those of the other phenothiazines tested: thioridazine and chlorpromazine (Ki = 88 and 91 microM, respectively), promazine and perazine (Ki = 322 and 341 microM, respectively), risperidone (Ki = 414 microM) or haloperidol (Ki = 606 microM). The investigated neuroleptics--when given to rats in vivo for one day or two weeks--did not produce any indirect effect on CYP2C6 via other mechanisms, except for levomepromazine, which increased the activity of the enzyme after 24-h exposure. Therefore, the direct inhibitory effect of levomepromazine on CYP2C6 may be attenuated by an indirect mechanism at the beginning of the neuroleptic therapy. In summary, the obtained results show direct inhibitory effects of some phenothiazine neuroleptics and sertindole on the activity of CYP2C6 in vitro in rat liver microsomes. Considering relatively high pharmacological doses and therapeutic concentrations of phenothiazines, it seems that the inhibitory effect of levomepromazine (and other phenothiazines with Ki values below 100 microM) found in vitro may be of physiological and pharmacological importance in vivo.     

The interaction between clonidine and various neuroleptic agents and some benzodiazepine tranquillizers*

The central hypotensive action of clonidine, infused into the vertebral artery of chloralose-anaesthetized cats was antagonized by several phenothiazine-neuroleptics (chlorpromazine, promazine, promethazine, thiethylperazine, thioridazine), by chlorprothixene and to a limited extent by haloperidol administered via the same route. Pimozide and some benzodiazepines (chlordiazepoxide, diazepam and flurazepam) hardly influenced the central hypotensive response to clonidine. The antagonism between clonidine and the psychotropic drugs is probably associated with central α-adrenoceptors, clonidine being the agonist and the neuroleptic agents the antagonists at these receptors. Virtually the same type of antagonism was observed in conscious, spontaneously hypertensive rats where both clonidine and the neuroleptic drugs were injected intravenously. The phenothiazines and also piperoxane effectively diminished the centrally induced hypotensive response to clonidine, whereas the initial pressor effect to clonidine was not reduced.     

The interaction between clonidine and various neuroleptic agents and some benzodiazepine tranquillizers.

The central hypotensive action of clonidine, infused into the vertebral artery of chloralose-anaesthetized cats was antagonized by several phenothiazine-neuroleptics (chlorpromazine, promazine, promethazine, thiethylperazine, thioridazine), by chlorprothixene and to a limited extent by haloperidol administered via the same route. Pimozide and some benzodiazepines (chlordiazepoxide, diazepam and flurazepam) hardly influenced the central hypotensive response to clonidine. The antagonism between clonidine and the psychotropic drugs is probably associated with central alpha-adrenoceptors, clonidine being the agonist and the neuroleptic agents the antagonists at these receptors. Virtually the same type of antagonism was observed in conscious, spontaneously hypertensive rats where both clonidine and the neuroleptic drugs were injected intravenously. The phenothiazines and also piperoxane effectively diminished the centrally induced hypotensive response to clonidine, whereas the initial pressor effect to clonidine was not reduced.     

Dose-related response of mouse mamma to some phenothiazine drugs.

The dose-related response of the mammary growth was studied in immature ICR-JCL female mice given 0.03 micrograms of estradiol per animal subcutaneously, and 0.005-1.0mg of either of the following phenothiazines (chlorpromazine, levometh iomeprazine, promethazine, perphenazine, thioridazine and propericiazine) per 10g of body weight was given orally once a day for 9 days starting on the 5th day after ovariectomy. The right second mamma of the chest was used to compare the hypertrophic affects. All the phenothiazines used produced mammary growth in the intensity sequence of thioridazine greater than chlorpromazine greater than promethazine greater than propericiazine greater than perphenazine greater than levomethiomeprazine. An optimal dose of each of the phenothiazines required to produce the maximum hypetrophy of the mammary gland was examined. From the results obtained, the relationship between the side-chain moiety of the compounds and the mammary growth activity could not be revealed.     

Study of the metabolism of phenothiazines: determination of N-demethylated phenothiazines in urine

When phenothiazine drugs (chlorpromazine, promazine, promethazine, propiomazine, propionylpromazine, trifluoperazine and trimeprazine) were reacted with m-chloroperbenzoic acid, N-demethylated phenothiazines were obtained in moderate yield. The mass spectra of the N-demethylated phenothiazines showed either m/z 44 and 72 or m/z 58 as characteristic ions depending on their side chain. The N-demethylated propiomazine was identified as a metabolite of propiomazine from the urine of a rat which was given propiomazine orally.     

The antibacterial effect of some neuroleptics on strains isolated from patients with meningitis.

Eighty-two strains of bacteria (Neisseria meningitidis, Haemophilus influenzae, Enterobacteriaceae, Streptococcus pneumoniae, group B streptococci and Listeria monocytogenes) were examined for their in vitro susceptibility to eight drugs, seven neuroleptics (perphenazine, fluphenazine, cis(Z)-clopenthixol, haloperidol, clozapine, clebopride and SCH 23390), and the neuroleptically inactive trans(E)-clopenthixol. The phenothiazines and the thioxanthenes were, on the whole, the most active drugs when measured, the IC50(50) for each group of bacteria being 7.4 to 84 mg/l (with the exception of the activity against the enterobacteriaceae). The antibacterial potency of clozapine, which has an atypical neuroleptic profile, was between 50 and 140 mg/l. Haloperidol also showed an antibacterial activity in the concentration range 35-140 mg/l. The selective D1 antagonist, SCH 23390 and the selective D2 antagonist, clebopride, inhibited only few of the bacteria in the concentration range investigated.     

HRE 664, a new parenteral penem. I. Antibacterial activity in vitro

The new penem antibiotic HRE 664 displays potent antibacterial activity in vitro against a broad spectrum of clinically relevant bacterial strains including Gram-negative and Gram-positive aerobes and anaerobes. With an MIC 90% of 0.43 micrograms/ml, it is also active against methicillin-resistant staphylococci. HRE 664 is extremely stable against beta-lactamases, it binds preferentially to the penicillin-binding proteins 2, 3, 5 and 6 of Escherichia coli.     

Differences between antipsychotic drugs in persistence of brain levels and behavioral effects

After a single dose of the butyrophenone neuroleptic haloperidol, behavioral effects and detectable drug levels in rat brain can last for several weeks. To determine if such persistence is a general property of neuroleptics, we compared drug levels and effects after IP administration of two butyrophenones (haloperidol and bromperidol), a high potency (fluphenazine) and a low potency (chlorpromazine) phenothiazine. Drug levels in brain tissue were measured by high pressure liquid chromatography and behavioral effects monitored as inhibition of apomorphine-induced stereotypy. Estimated near terminal elimination half-lives (t_1/2) from brain for acutely administered chlorpromazine (20 mg/kg) and fluphenazine (1 mg/kg) were 0.41 and 0.62 days, respectively, and neither drug was detectable after 4 days. Fluphenazine given daily for 5 days showed an only slightly slower elimination (t_1/2=1.1 days). In contrast, near-terminal elimination half-lives from brain for haloperidol and bromperidol (both at 1 mg/kg, IP) were much longer (6.6 and 5.8 days, respectively), and each was detectable for 21 days after dosing. Inhibition of apomorphine-induced stereotypy correlated highly (r=0.95) with brain levels of haloperidol. For fluphenazine, given once or repeatedly, early inhibition was replaced within 1 week by supersensitivity to apomorphine which persisted for up to 3 weeks. These findings, indicating marked differences in clearance and recovery times after dosing with butyrophenones and phenothiazines, have clear implications for studies of the effects of neuroleptic drugs in rats. While there are limits to the extrapolation of these findings to other species, our results and those from studies in human subjects suggest similarly persistent drug levels and effects may be seen when patients are withdrawn from neuroleptic drugs.     

Effects of various drugs on superoxide generation, arachidonic acid release and phospholipase A2 in polymorphonuclear leukocytes

The effects of variety of drugs on metabolic burst and phospholipase A2 in polymorphonuclear leukocytes (PMNs) were investigated. The stimulation of PMNs by n-formyl-methionyl-leucyl-phenylalanine (FMLP) causes arachidonic acid (AA) to be released in the cells concomitantly with the generation of superoxide anion. These variables were effectively diminished with some clinically employed drugs including chlorpromazine, trifluoperazine, azelastine, clemastine and mepacrine at the lower concentration of 20 microM. In contrast, indomethacin and procaine were ineffective even at the higher concentration of 100 microM. Subcellular fractionation of PMNs revealed that phospholipase A2 activity was located both in the plasma membrane-rich fraction as well as the granule-microsome-rich fraction, and the potency of inhibition of membrane-bound phospholipase A2 by the above mentioned drugs was: indomethacin (IC50 = 3 microM) less than chlorpromazine less than azelastine and clemastine (IC50 greater than 100 microM). The low potency of antipsychotropic drugs and antihistaminic drugs in inhibiting the fractionated phospholipase A2 contrast with the high efficiency with which they inhibit the superoxide generation and the AA release from stimulated PMNs. The AA releases from the PMNs stimulated by FMLP or calcium ionophore (A23187) were almost equally diminished by various drugs at the lower concentration. From these observations, it appeared likely that these drugs might inhibit the metabolic stimulations of PMNs at the sites of the Ca2+-dependent activation processes of the enzymes responsible for the AA release and the superoxide generation.     

In vitro antibacterial activity of drugs against human intestinal anaerobic bacteria.

The in vitro antibacterial activity, against the major groups of anaerobic fecal bacteria, of a series of drugs was examined by an agar diffusion test and the minimum inhibitory concentration (MIC) test. Only the phenothiazines and amitriptyline showed any marked antibacterial activity, the MIC's being in the 40-640-mu-g/ml range. It is suggested that the detergent nature of the molecules of these drugs in aqueous solution is responsible for the observed antibacterial activity.     

Extractive-spectrophotometric determination of some 2- and 10-disubstituted phenothiazines with dipicrylamine.

Dipicrylamine reacts in neutral medium with some 2,10-disubstituted phenothiazines (promazine, chlorpromazine and promethazine hydrochlorides, trifluoperazine dihydrochloride, thioproperazine dimethanosulphonate) forming orange or brown ion-association compounds. The compounds are insoluble in water but quantitatively extracted into chloroform. These properties have been exploited for the determination of phenothiazines in pure solutions and pharmaceuticals.     

In vitro human plasma leucine(5)-enkephalin degradation is inhibited by a select number of drugs with the phenothiazine molecule in their chemical structure

A number of drugs with the phenothiazine molecule in their chemical structure inhibit in a dose-dependent manner human plasmatic aminopeptidase leucine(5)-enkephalin (LEU) metabolism. Half-life peptide degradation was significantly increased by thioridazine > fluphenazine > As-1397 [10-(alpha-diethylaminopropionyl)phenothiazine] >/= promethazine >/= chlorpromazine (final drug conc. 10(-4) M); t1/2 (+/- SD) 21.2 +/- 1.1, 19.6 +/- 1.0, 17.2 +/- 0.9, 17.1 +/- 1.0, and 17.1 +/- 1.1 min, respectively. Control and bacitracin (known aminopeptidase inhibitor) values were 11.8 +/- 1.0 and 31.3 +/- 1.7 min, respectively. These drugs significantly decreased (listed in the same order) LEU degradation initial velocity; Iv (+/- SD) 0.77 +/- 0.2, 0.82 +/- 0.2, 0.92 +/- 0.3, 0.93 +/- 0.2, 0.94 +/- 0.3 pg LEU/min, respectively. Control and bacitracin 1.10 +/- 0.3 and 0.20 +/- 0.1 pg LEU/min, respectively. Values represent results from 5 samples, each obtained by pooling 6 individual plasmas (4 male and 2 female; n = 30 healthy, drug-free volunteers). However, neither the phenothiazines ethopropazine, methotrimeprazine, prochlorperazine and trifluoperazine nor the various commonly used heterocyclic antipsychotics tested, e.g., molindone, loxapine, clozapine, haloperidol, sulpiride and thiothixene inhibited plasma LEU degradation kinetics. Our results failed to show correlations between chemical structure, antipsychotic properties and ability to inhibit plasmatic aminopeptidase LEU degradation. Whereas, presence of the phenothiazine molecule appears to be necessary for enzyme inhibition, only five out of nine substituted phenothiazines tested exhibited this effect. Furthermore, there was a lack of correlation between phenothiazines antipsychotic properties and their capacity to inhibit aminopeptidase activity, a property shown by promethazine (antihistaminic) and As-1397 (selective butyrylcholinesterase inhibitor) but lacking in prochlorperazine and trifluoperazine. Our results provide information which could lead to the rational design of agents capable to modulate the bioavailability of enkephalin and other endogenous aminopeptidase-degraded peptides believed to be involved in the etiology and/or pathophysiology associated with various disease conditions. Whether their development could find useful pharmacological applications remains to be explored.     

Effects of thiazinamium chloride, promethazine and chlorpromazine on thromboxane B2 synthesis, phagocytosis and respiratory burst by rat alveolar macrophages

The effects of three phenothiazines, promethazine, thiazinamium chloride and chlorpromazine, on macrophage function were investigated in rat alveolar macrophages. The study focused on thromboxane B2 (TxB2) synthesis, zymosan phagocytosis, and hexosemonophosphate (HMP) shunt activity in these phagocytes. TxB2 synthesis by resting macrophages was inhibited by thiazinamium chloride and promethazine in a dose-dependent manner. However, chlorpromazine was inhibitory only at 10(-3) M. Promethazine treatment of zymosan-activated macrophages led to a concomitant reduction in both phagocytosis and TxB2 synthesis. Thiazinamium chloride inhibited TxB2 synthesis but had no effect on the ingestion of zymosan particles. In contrast, chlorpromazine inhibited phagocytosis but not TxB2 synthesis except at 10(-3) M. The effects of these agents on the formation of TxB2 synthesis from exogenous arachidonic acid were also investigated. Under these conditions where indomethacin, a known cyclooxygenase inhibitor, was inhibitory, promethazine but not thiazinamium chloride inhibited TxB2 synthesis from exogenous arachidonic acid. Treatment of macrophages with promethazine and chlorpromazine but not thiazinamium chloride results in a reduction in the oxidative burst during phagocytosis. The results suggest that the phenothiazines used in this study differ from one another in their actions on macrophage function. Furthermore, the ability of thiazinamium chloride to selectively inhibit arachidonic acid metabolism may contribute to its bronchodilator/antiallergic activity.     

Comparative in vitro activity of phenothiazines against multidrug-resistant Mycobacterium tuberculosis

The comparative activity of five phenothiazines against multidrug-resistant strains of Mycobacterium tuberculosis (MDRTB) was studied using the Bactec 460 system. The order of antimycobacterial activity of the phenothiazines was: chlorpromazine = thioridazine > promethazine > promazine = desipramine. However, the levels required for an MIC 50 exceeded 1 mg/l and are beyond those that are clinically achievable. As phenothiazines are concentrated by macrophages that phagocytose and have in situ activity against mycobacteria, these agents may be considered for use as adjuvants for the management of freshly diagnosed tuberculosis in patients from populations with a high prevalence of MDRTB.     

Chlorpromazine and related phenothiazines inhibit the ATP-sensitive K+ channel.

Whole-cell, current clamp, single channel recordings and 86Rb+ flux techniques were used to show that phenothiazines inhibit ATP-sensitive K+ channels (KATP) in HIT-T15 beta-cells. Chlorpromazine inhibition was observed when KATP channels were activated by ATP depletion or by direct treatment with a classical KATP channel opener, diazoxide. The order of potency of the phenothiazines tested was chlorpromazine greater than triflupromazine greater than fluphenazine greater than trifluopromazine with IC50 values of 1, 4, 6 and 20 microM, respectively. The inhibition was reversible.     

Chlorpromazine, methotrimeprazine, and metabolites. Structural changes accompanying the loss of neuroleptic potency by ring sulfoxidation

The 3-dimensional molecular structures of methotrimeprazine, methotrimeprazine sulfoxide, and chlorpromazine sulfoxide were examined by X-ray crystallography. Previous studies of their dopamine receptor binding affinities have indicated that both chlorpromazine sulfoxide and methotrimeprazine sulfoxide lack neuroleptic potency. The crystal structures of methotrimeprazine and its sulfoxide were similar to the previously published structure of chlorpromazine. The sulfoxide metabolite of chlorpromazine, on the other hand, had a different conformation of the side chain. A boat axial conformation of the sulfoxy group was found for both metabolites. The crystal structures suggest that the apparent loss of neuroleptic potency by biotransformation of the phenothiazine drugs to their ring sulfoxides is caused by the introduction of the sulfoxide group itself, and not by concurrent conformational changes in the rest of the molecule.     

In vitro studies with Bay V 3522, a new oral cephalosporin

The in vitro activities of Bay v 3522, cefaclor, cephalexin, cefuroxime, cefixime, amoxicillin/clavulanate (2:1) and reference penicillins were compared against 314 clinical isolates of Gram-positive and Gram-negative bacteria and nine strains of Escherichia coli that differed in their outer membrane proteins in agar dilution tests with an inoculum of 10(4) cfu/spot. The beta-lactamase stabilities of the cephalosporins were also evaluated by spectrophotometric assay using 21 different beta-lactamases. Bay v 3522 was the most potent cephalosporin overall against Gram-positive pathogens, but slightly less active than amoxicillin/clavulanate. In addition to being highly active against streptococci (MIC90 = 0.25 micrograms/ml) and methicillin-susceptible staphylococci (MIC90 = 1.0 micrograms/ml), Bay v 3522 was markedly more active than the other cephalosporins against Enterococcus faecalis (MIC90 = 4 micrograms/ml). Bay v 3522 was less potent against Gram-negative pathogens, especially nosocomial isolates of Escherichia coli and Klebsiella pneumoniae (MIC90 greater than 64 micrograms/ml), but was active against Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and beta-lactamase-negative Neisseria gonorrhoeae (MIC90 = 1.0 micrograms/ml0. Hydrolysis of Bay v 3522 by most beta-lactamases examined was significantly less than that observed for cephalothin and cefaclor; similar to that observed with cephalexin; and less than that observed with cefixime and cefuroxime. None of the beta-lactamases examined hydrolysed Bay v 3522 at a rate greater than 20 nmol/min/mg. The in vitro potency of Bay v 3522 against Gram-positive and fastidious Gram-negative pathogens and its resistance to hydrolysis by beta-lactamases produced by them support further investigation of this cephalosporin as a new oral therapeutic agent.