Chlorpromazine Sulphoxide Research Articles

The metabolites of chlorpromazineN-oxide in rat bile

1. The metabolism of chlorpromazine N-oxide was studied in female rats after a 20 mg/kg single i.p. dose. 2. Metabolites identified in urine and faeces were chlorpromazine, 7-hydroxychlorpromazine, chlorpromazine sulphoxide, N-desmethylchlorpromazine and N-desmethylchlorpromazine sulphoxide. As these same five metabolites were previously shown to be present after oral administration this indicates that reduction of chlorpromazine N-oxide occurs not only in the gastrointestinal tract but also at other sites. 3. The metabolism of chlorpromazine N-oxide was studied following its administration by either i.p., i.v. or oral routes to female rats in which the bile duct was cannulated. 4. There were no qualitative differences between the three routes of administration with respect to the metabolites identified. With the exception of the absence of N-desmethylchlorpromazine and N-desmethylchlorpromazine sulphoxide, all metabolites previously identified in urine and faeces were also present in bile. 5. Additionally there were three compounds present in rat bile which were not identified in urine or faeces. These were chlorpromazine N-oxide, chlorpromazine N,S-dioxide and 7-hydroxychlorpromazine O-glucuronide. This is the first unequivocal evidence for the identification of intact 7-hydroxychlorpromazine O-glucuronide in any species. 6. The inability to detect chlorpromazine N-oxide and chlorpromazine N,S-dioxide in the faeces of rats is likely to be due to the reduction of the N-oxide group on the passage of these biliary metabolites down the intestinal tract.

High-performance liquid chromatographic determination of chlorpromazine and its degradation products in pharmaceutical dosage forms: a stability-indicating assay.

A high-performance liquid chromatographic method has been developed for the determination of chlorpromazine and its degradation products, chlorpromazine sulphoxide and chlorpromazine sulphone. The method utilises reversed-phase chromatography with selective fluorescence detection and internal calibration techniques. The method shows fluorescence selectivity for chlorpromazine sulphoxide and chlorpromazine sulphone at 385 nm with no interference from the chlorpromazine peak. The method has been used to study a variety of samples from sources in Zimbabwe. Tablet samples showed little degradation whereas some injection samples had levels of chlorpromazine sulphoxide in excess of 5%(i.e., greater than the maximum allowed in the USP). The developed method was compared with the official BP method for chlorpromazine determination.

Correlation of activity of chlorpromazine and respective hydroxy, dimethoxy and sulphoxide analogues on dopamine, muscarinic, histamine and calmodulin sites of action.

1. Chlorpromazine (CPZ) is a unique molecule which has many potential sites of action, as well as a propensity to be transformed into a host of metabolites possessing varying degrees of pharmacological and/or toxic reactions. This investigation examined the rank order of potency of CPZ and eight metabolic derivatives with respect to displacement of 3H-spiperone at central dopamine-2 (DA-2) receptors, 3H-pirenzepine at central muscarinic-1 (M-1) receptors, and inhibition of calmodulin-induced activation of cyclic AMP-dependent phosphodiesterase. 2. The most potent CPZ analogues to displace labelled spiperone from DA-2 receptors in rat striatum were: 3-hydroxy-CPZ, CPZ, 3,7-dihydroxy-CPZ, and 7-hydroxy-CPZ. Intermediate potency was observed with 8-hydroxy-CPZ, 3,7,8-trihydroxy-CPZ, and 7,8-dihydroxy-CPZ. Chlorpromazine sulphoxide and 7,8-dimethoxy-CPZ displayed the least activity at DA-2 receptors. 3. Displacement of labelled pirenzepine from M-1 receptors in rat frontal cortex occurred to the greatest extent with CPZ which was one to two orders of magnitude more potent than noted for 3-hydroxy-CPZ greater than 7-hydroxy-CPZ greater than CPZ-sulphoxide greater than 8-hydroxy-CPZ greater than 7,8-dimethoxy-CPZ. The least potent agents were 3,7-and 7,8-dihydroxy-CPZs and 3,7,8-trihydroxy-CPZ. 4. A partially purified calmodulin-sensitive preparation of cyclic AMP-dependent phosphodiesterase from guinea pig heart was most sensitive to inhibition by 7,8-dihydroxy-CPZ, 7,8-dimethoxy-CPZ, 3-hydroxy-CPZ, 7-hydroxy-CPZ, 8-hydroxy-CPZ and CPZ. Least inhibition occurred with 3,7-dihydroxy-CPZ, 3,7,8-trihydroxy-CPZ and CPZ-sulphoxide. 5. The DA-2 receptors were more sensitive to the active CPZ analogues than were the M-1 receptors while calmodulin-activated phosphodiesterase was the least sensitive preparation. 6. Comparisons of data were made with existing information from other laboratories and in general CPZ, 7-hydroxy-CPZ and 3-hydroxy-CPZ were the most potent compounds across different test conditions.

The metabolism of chlorpromazine N-oxide in the rat.

1. The metabolism of chlorpromazine N-oxide was studied in female rats after a 20 mg/kg single oral dose. 2. Metabolites identified in both urine and faeces were chlorpromazine, 7-hydroxychlorpromazine, chlorpromazine sulphoxide, N-desmethylchlorpromazine and N-desmethylchlorpromazine sulphoxide. 3. Metabolites were separated by h.p.l.c. or g.l.c. prior to mass spectrometric analysis. The structures of the metabolites were confirmed by direct comparison of their mass spectra and chromatographic behaviours with those of authentic compounds. 4. Chlorpromazine N-oxide and any metabolite which retained the intact N-oxide function, such as chlorpromazine, N,S-dioxide, could not be identified in any of the extracts. 5. When 3H-chlorpromazine N-oxide was administered under the same conditions; approximately twice as much radioactivity was excreted in the faeces (52.1 +/- 9.7%) as in the urine (26.9 +/- 7.2%).

Effect of variation of temperature on second-derivative fluorescence spectra. Part II. Effect of experimental parameters on the observed temperature coefficients

The effects of varying a number of experimental parameters on the temperature coefficients of the second-derivative fluorescence spectral amplitudes of chlorpromazine sulphoxide in pH 8 borate buffer have been investigated. The temperature coefficients were found to decrease with increasing concentration and with increasing scan speed, to increase with increasing excitation and emission slit widths and to vary widely with the wavelengths at which the measurements were made. These effects are discussed in relation to the observed or theoretical changes that occur in the fundamental spectra as a result of variation of the experimental parameters.

Chlorpromazine, but not chlorpromazine sulphoxide, stimulates transmitter release from motor nerve terminals

Treatment of frog neuromuscular preparations with chlorpromazine (5 μmol/l) resulted in a marked rise in miniature endplate potential (MEPP) frequency of >100% within 30 min, and an increase in evoked transmitter release (quantal content 5–15) of about 35%. Treatment with chlorpromazine sulphoxide (5 μM), a derivative of chlorpromazine with a much lower affinity for calmodulin, had very little effect on either form of transmitter release. It is concluded that stimulatory effects of calmodulin-binding drugs at the nerve terminal may well be exerted through calmodulin inhibition. The stimulatory effect of chlorpromazine on MEPP frequency was markedly reduced in preparations bathed in EGTA-containing Ca 2+-free saline, but the response was largely restored by raising the temperature by 3–4 °C. It is argued that despite this partial dependence on [Ca 2+]**, stimulation of transmitter secretion by chlorpromazine is likely to be mediated by inhibition of calmodulin-activated Ca 2+-ATPases and consequent elevation of [Ca 2+]**.

Postsynaptic inhibitory effects of phenothiazines at cholinergic synapses may not involve calmodulin.

Treatment of frog cutaneous-pectoris nerve-muscle preparations with calmidazolium (R 24571), a calmodulin-inhibitor, at concentrations of 2 X 10(-7) mol/l and 5 X 10(-7) mol/l had no discernable effect on MEPP amplitude. 10(-6) mol/l calmidazolium caused a small (10-35%) increase in MEPP amplitude in most preparations. The phenothiazine calmodulin-inhibitor chlorpromazine (5 X 10(-6) mol/l) caused a clear reduction in MEPP amplitude (20%) after 30 min treatment. Similar experiments carried out with chlorpromazine sulphoxide (a derivative of chlorpromazine that is 60 X less potent in inhibition of calmodulin-activated enzymes) produced data that were very similar to those obtained with chlorpromazine. It is concluded that the postsynaptic inhibitory effect of phenothiazines at cholinergic synapses is unlikely to involve calmodulin.

Phenothiazine drugs and metabolites: Molecular conformation and dopaminergic, alpha adrenergic and muscarinic cholinergic receptor binding

The solid state molecular structures of methoxypromazine and N-monodesmethyl chlorpromazine sulphoxide were determined by X-ray crystallography, as an extension of previous studies on the molecular structures of chlorpromazine sulphoxide and methotrimeprazine sulphoxide. The binding affinities of phenothiazine drugs and metabolites with known crystal structures to dopaminergic, alpha adrenergic and muscarinic cholinergic receptors in rat brain were examined using radio-ligand binding techniques. Comparison of their solid state molecular structures and potencies in neurotransmitter receptor binding reveals that these compounds exist in two different conformations: One, associated with low biological activity, has an angle between the planes of the two aryl rings in the range of 155–160°, and a torsion angle of −80 to −84° around the N(10)-C bond of the side-chain, calculated from the substituted benzene ring. In the other conformation, which is found in the biologically active derivatives, the angle between the planes of the two aryl rings is in the range of 134–145°, and the torsion angle around the N(10)-C bond of the side-chain is in the range of 64–69° or 129–144°. The “active” and “inactive” conformations thus have the side-chain on opposite sides of the ring system.

The structures of (dimethylaminopropyl)phenothiazine drugs and their metabolites. II. Chlorpromazine sulphoxide, C17H19ClN2OS, at 120 K

The structures of (dimethylaminopropyl)phenothiazine drugs and their metabolites. II. Chlorpromazine sulphoxide, C17H19ClN2OS, at 120 K

Pharmaceutical applications of variable-angle synchronous scanning fluorescence spectroscopy

The development of variable-angle synchronous scanning (v.a.s.s.) in fluorescence spectrometry is reported, based on a computer-aided spectrofluorimeter. The technique permits a linear path to be scanned at any preselected angle through the emission-excitation matrix defined by ( I em, λ em, λ ex), by effectively scanning the emission and the excitation monochromators at different speeds under computer control. When applied to pharmaceutical dosage forms, v.a.s.s. gave good selectivity for chlorpromazine in the presence of its principal degradation product, chlorpromazine sulphoxide, and for oxytetracycline in the presence of the additives vitamin C, thiamine, nicotinamide and riboflavin. Good calibration linearity, precision and recovery were observed for both principal drug components. The angle of the scan trajectory can also be varied continuously through the emission-excitation matrix, to describe any desired path under computer control. This novel technique of non-linear v.a.s.s. can provide an improved method for generating diagnostic profiles of drugs, degradation products and metabolites.

On the calcium receptor activating exocytosis: inhibitory effects of calmodulin-interacting drugs on rat mast cells.

1. A series of neuroleptic drugs (five phenothiazines, imipramine, and pimozide) and the smooth muscle relaxant W-7, which all inhibit calcium-calmodulin-activated processes inhibited rat mast cell secretion elicited by antigen, by 48/80, and by the calcium ionophore A23187. 2. Neither the phenothiazines nor W-7 reduced 45Ca uptake in response to A23187. The drugs thus exert an inhibitory action distal to the rise in intracellular Ca ions that activates exocytosis. 3. Chlorpromazine sulphoxide, which shares several membrane-perturbing actions of the phenothiazines but is a weak inhibitor of calmodulin, did not inhibit secretion. Moreover, the inhibitory effects of the phenothiazines were not overcome by a 5- or 10-fold increase in the concentration of calcium, which should counter unspecific membrane effects. 4. The inhibitory effects of the various neuroleptic drugs appeared to be related to their ability to inhibit calmodulin because the individual potencies of these compounds on secretion evoked by 48/80 or A23187 correlated significantly with their reported potencies in inhibiting calmodulin-activated processes. (The greater potency and different rank order of these compounds on secretion evoked by antigen suggests an additional inhibitory action, perhaps involving Ca entry.) 5. These results, which parallel those obtained with drugs of this sort in smooth muscle where calmodulin seemingly functions as the Ca receptor activating contraction, strengthen the view that calmodulin, or some calmodulin-like protein, is the Ca receptor activating exocytosis.

The effect of the photodecomposition of chlorpromazine on lecithin monolayers.

Chlorpromazine hydrochloride (cpz) is decomposed when irradiated with ultraviolet light, forming H+, hydrochloric acid, chlorpromazine sulphoxide and 2-hydroxypromazine. The order of the reaction (as measured by the expansion that is produced in a lecithin/cpz monolayer) varies between zero and about 3/4. The results have been used to explain some of the adverse side effects that are observed when patients are treated with cpz.

Correlation between plasma chlorpromazine and its metabolites and clinical ratings in patients with acute relapse of schizophrenic and paranoid psychosis.

Nine patients diagnosed as having acute schizophrenic psychosis were treated with chlorpromazine. Their clinical response to drug treatment was measured by the use of a clinical rating scale developed from the Present State Examination, and a nurses rating scale. Plasma levels of chlorpromazine (CPZ), 7-hydroxychlorpromazine (7OHCPZ), monodesmethylchlorpromazine (NOR1CPZ) and chlorpromazine sulphoxide (SOCPZ), were monitored during the period of hospital treatment. Correlations were made between the increase in plasma levels of drug or metabolites and improvement in the different PSE scores. These showed that the most significant correlations occurred when symptoms with high diagnostic significance for schizophrenia (Group 1) and symptoms rating perceptual disorders (P) were correlated with plasma 7OHCPZ levels in plasma samples taken before the first morning dose of CPZ. The ration of 7OHCPZ to CPZ in these samples increased significantly as clinical ratings improved, this correlation being most highly significant against the Group 1 and P scores. The ratio of 7OHPCZ to SOCPZ increased significantly only in the case of Group 1 and P scores. This indicates a preferential shift of CPZ metabolism towards the formation of the active 7OHCPZ during the period of clinical improvement.

Formation of chlorpromazine sulphoxide and monodesmethylchlorpromazine by microsomes of small intestine.

The metabolism of chlorpromazine by microsomal preparations of the small intestine from guinea pig and rat was studied. 35S-chlorpromazine was incubated with these preparations in Krebs-Ringer bicarbonate buffer at 37 degrees C. Control values were obtained by performing the assay at 0 degrees C. The metabolites were extracted with dichloroethane and separated by TLC. In incubations with intestinal microsomes from guinea pigs chlorpromazine sulphoxide and monodesmethyl chlorpromazine were identified as main metabolites. The apparent Michaelis constant for sulphoxidation of chlorpromazine is approximately 20-30 micronM and for N-demethylation in the range of 30-100 micronM. Using microsomal preparations from rat intestine, however, noteworthy formation of chlorpromazine metabolites could not be found. This observation can be explained by the fact that the cytochrome P450 content of rat intestinal microsomes was extremely low compared with that determined in guinea pig microsomes.

Clinical significance of plasma chlorpromazine levels. I. Plasma levels of the drug, some of its metabolites and prolactin during acute treatment.

Seventeen acute psychotic patients were studied in the course of chlorpromazine (CPZ) treatment. Blood samples were taken weekly both before and two hours after the morning CPZ dose. Plasma levels of CPZ, CPZ sulphoxide (CPZ SO) monodesmethylated CPZ (NOR1CPZ) and 7-hydroxy CPZ (7OH CPZ) were estimated by gas chromatography. Plasma prolactin, luteinizing hormone, testosterone and oestrogens were measured by radioimmunoassay. Six of the seven patients who showed no clinical improvement had plasma CPZ levels equal to or higher than those of patients who improved. 'Non-responders' has a greater proportion of CPZ SO in pre-dosage samples. The occurrence of parkinsonian side effects was associated with a mean plasma CPZ of greater than 50 ng/ml and a mean plasma prolactin of greater than 30 ng/ml two hours after dosage. The elevation of prolactin preceded the onset of parkinsonian symptoms by 1-2 weeks. There was a significant positive correlation between mean plasma prolactin and mean plasma CPZ levels. The prolactin response may prove a useful index of the central antidopaminergic effect of neuroleptic drugs.

Inhibition of 5-hydroxytryptamine-induced human blood platelet aggregation by chlorpromazine and its metabolites.

1 Blood platelets from normal human subjects were isolated and aggregated in vitro with adenosine diphosphate (ADP) or 5-hydroxytryptamine (5-HT). 2 The effects of chlorpromazine and 7 major metabolites upon 5-HT-induced aggregation were investigated. 3 All the phenothiazines inhibited 5-HT-induced aggregation when added to platelet rich plasma 3 min prior to 5-HT. 4 There were no qualitative differences in the inhibitory effects, but inhibitory potency varied over a wide range. The decreasing order of potency was monodesmethylchlorpromazine, chlorpromazine, 7-hydroxychlorpromazine, didesmethylchlorpromazine, 3,7 -dimethoxy-chlorpromazine, didesmethylchlorpromazine sulphoxide, chlorpromazine sulphoxide, chlorpromazine nitroxide.

THE RELATIONSHIP OF PLASMA CHLORPROMAZINE TO ITS 7‐HYDROXY AND SULPHOXIDE METABOLITES IN A LARGE POPULATION OF CHRONIC SCHIZOPHRENICS

1 Blood samples were obtained from eighty-six chronic schizophrenics receiving a wide range of oral doses of chlorpromazine. Plasma concentrations of chlorpromazine, 7-hydroxychlorpromazine and chlorpromazine sulphoxide were estimated using a sensitive gas-liquid chromatographic method and their relationships to oral dose and to global clinical control were investigated.2 Wide variability was observed in the plasma concentrations of unchanged drug and metabolites between patients receiving similar daily doses.3 In general the plasma concentrations of the 7-hydroxy and sulphoxide metabolites were of similar magnitude to the concentrations of chlorpromazine.4 Global symptom control was unrelated to the plasma concentration of unchanged chlorpromazine. However, patients judged to be under good control had relatively higher concentrations of the biologically active 7-hydroxy metabolite in their plasma than patients who were poorly controlled and in whom the biologically inactive sulphoxide metabolite predominated. When the ratio of 7-hydroxychlorpromazine to chlorpromazine sulphoxide was derived for each patient, a highly significant difference was found to exist between the metabolite ratios of patients grouped according to clinical control.5 It is suggested that a prediction of therapeutic response to chlorpromazine may be provided in the form of the ratio of the plasma concentration of biologically active metabolite to the concentration of either the unchanged drug or its inactive metabolite.

Inhibition of the catalytic site of adenylate cyclase in the central nervous system by phenothiazine derivatives

Inhibition by phenothiazine derivatives was evaluated with respect to the catalytic component of adenylate cyclase prepared from either a high speed particulate fraction of rat cerebral cortex and hypothalamus or neuronal and glial-enriched fractions from rat and rabbit cerebral cortex. The dihydroxylated analogues of chlorpromazine, prochlorperazine, perphenazine and promazine along with the dioxo form of chlorpromazine were the most potent inhibitors of either basal activity or fluoride activation of the enzyme. To a lesser extent inhibition of adenylate cyclase was observed with the parent compounds (including fluphenazine and promethazine) and their respective monohydroxylated or methoxylated analogues. The enzyme from the high speed particulate fraction was more resistant to inhibition by these compounds than the neuronal and glial enzymes. Compounds which were without effect on adenylate cyclase were: chlorpromazine sulphoxide, haloperidol, phenothiazine, 3-hydroxyphenothiazine and 2-chloro-7,8-dioxophenothiazine. A preliminary investigation revealed that 7,8-dihydroxychlorpromazine and 7,8-dioxochlorpromazine exerted profound antagonism of norepinephrine sensitive adenylate cyclase in neuronal and glialenriched fractions. In this regard chlorpromazine and 7-hydroxychlorpromazine displayed an intermediate potency while 8-hydroxychlorpromazine was a weak antagonist of the enzyme. Chlorpromazine sulphoxide and 7,8-dimethoxychlorpromazine were without an effect. The data suggest that the actions of specific metabolites of phenothiazines may account for additional intracellular effects following experimental or therapeutic administration of any parent compourd.

A polarographic method for the determination of the N-oxide, N-oxide-sulphoxide and sulphoxide metabolites of chlorpromazine.

Abstract Cathode ray polarography has been used to measure chlorpromazine-N-oxide, N-oxide sulphoxide and chlorpromazine sulphoxide in mixtures. The response was linear when the metabolites were present in the range 10−5 to 5 times 10−8m in aqueous solutions. Reductive polarography of the mixed oxides in solution gave an additive wave from which individual oxides were determined by subtraction. Ultraviolet and Potentiometrie titration methods were used to determine the pKa values of the oxide metabolites of chlorpromazine. The mechanism of the reduction process was investigated using d.c. polarography and preparative micro-electrolysis. Polarographic analysis was applied to the determination of the metabolites after their separation from urine, plasma and microsomal preparations.

Stimulation of calcium uptake of muscle microsomes by phenothiazine and barbiturates

The calcium pump of sacroplasmic reticulum of rabbit and frog is stimulated by phenothiazines in the concentration range 10–100 μM, and by barbiturates in the concentration range 0.5–4.0 mM at 25°C. When potassium, which is an intracellular activator of the calcium pump, is incorporated in the medium in 100 mM concentration the phenothiazines, and less so the barbiturates, reduced the rate of calcium uptake. Chlorpromazine sulphoxide, a pharmacologically inactive metabolite of chlorpromazine, did not activate in the absence of potassium nor inhibit in its presence. Barbituric acid also was without effect. When the “extra” AtPase was measured during chlorpromazine-stimulated calcium uptake no increase in efficiency of the system was detected. It is hypothesized that phenothiazines and barbiturates function by reducing calcium loss from stimulated membranes, bathed by tissue fluid low in potassium, and so render them inexcitable.