Intracellular distribution of psychotropic drugs in the grey and white matter of the brain: the role of lysosomal trapping

1. Since the brain is not a homogenous organ (i.e. the phospholipid pattern and density of lysosomes may vary in its different regions), in the present study we examined the uptake of psychotropic drugs by vertically cut slices of whole brain, grey (cerebral cortex) and white (corpus callosum, internal capsule) matter of the brain and by neuronal and astroglial cell cultures. 2. Moreover, we assessed the contribution of lysosomal trapping to total drug uptake (total uptake=lysosomal trapping+phospholipid binding) by tissue slices or cells conducting experiments in the presence and absence of 'lysosomal inhibitors', i.e., the lysosomotropic compound ammonium chloride (20 mM) or the Na(+)/H(+)-ionophore monensin (10 microM), which elevated the internal pH of lysosomes. The initial concentration of psychotropic drug in the incubation medium was 5 microM. 3. Both total uptake and lysosomal trapping of the antidepressants investigated (imipramine, amitriptyline, fluoxetine, sertraline) and neuroleptics (promazine, perazine, thioridazine) were higher in the grey matter and neurones than in the white matter and astrocytes, respectively. Lysosomal trapping of the psychotropics occurred mainly in neurones where thioridazine sertraline and perazine showed the highest degree of lysosomotropism. 4. Distribution interactions between antidepressants and neuroleptics took place in neurones via mutual inhibition of lysosomal trapping of drugs. 5. A differential number of neuronal and glial cells in the brain may mask the lysosomal trapping and the distribution interactions of less potent lysosomotropic drugs in vertically cut brain slices. 6. A reduction (via a distribution interaction) in the concentration of psychotropics in lysosomes (depot), which leads to an increase in their level in membranes and tissue fluids, may intensify the pharmacological action of the combined drugs.

The influence of selective serotonin reuptake inhibitors on the plasma and brain pharmacokinetics of the simplest phenothiazine neuroleptic promazine in the rat

The aim of the present study was to investigate a possible impact of the three selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine and sertraline on the pharmacokinetics of promazine in a steady state in rats. Promazine was administered twice a day for 2 weeks, alone or jointly with one of the antidepressants. Concentrations of promazine and its two main metabolites (N-desmethylpromazine and sulfoxide) in the plasma and brain were measured at 30 min and 6 and 12 h after the last dose of the drugs. All the investigated SSRIs increased the plasma and brain concentrations of promazine up to 300% of the control value, their effect being most pronounced after 30 min and 6 h. Moreover, simultaneous increases in the promazine metabolites' concentrations and in the promazine-metabolite concentration ratios were observed. In vitro studies with liver microsomes of rats treated chronically with promazine, SSRIs or their combination did not show any significant changes in the concentrations of cytochromes P-450 and b-5. However, treatment with fluoxetine, alone or in a combination with promazine, decreased the rates of promazine N-demethylation and sulfoxidation. A similar effect was observed in the case of promazine and fluvoxamine combination. Kinetic studies into promazine metabolism, carried out on control liver microsomes in the absence or presence of SSRIs added in vitro, demonstrated competitive inhibition of both N-demethylation and sulfoxidation by the antidepressants. The results of in vivo and in vitro studies indicate the following mechanisms of the observed interactions: (a) competition for an active site of promazine N-demethylase and sulfoxidase; (b) adaptive changes in cytochrome P-450, produced by chronic treatment with fluoxetine or fluvoxamine; (c) additionally, increases in the sum of concentrations of promazine+ metabolites, produced by fluoxetine and sertraline in vivo, suggest simultaneous inhibition of another, not investigated by us, metabolic pathway of promazine, e.g. hydroxylation. In conclusion, all the three SSRIs administered chronically in pharmacological doses, increase the concentrations of promazine in the blood plasma and brain of rats by inhibiting different metabolic pathways of the neuroleptic. Assuming that similar interactions occur in humans, reduced doses of phenotiazines should be considered when one of the above antidepressants is to be given jointly.

Validated high-performance liquid chromatographic assay for the determination of promazine in human plasma. Application to pharmacokinetic studies

A high-performance liquid chromatographic method for the determination of promazine in human plasma is described. The assay involves a single-step liquid-liquid extraction using pentane-2-propanol (98:2, v/v). The analyte of interest and the internal standard chlorpromazine were separated on a Spherisorb CN column using a mobile phase of acetonitrile-50 mM ammonium acetate (9:1, v/v). Electrochemical detection was achieved using an applied potential of +750 mV. The assay was validated according to international requirements prior to application to a pharmacokinetic study and was found to be specific, accurate and precise with a linear range of 0.25-25 ng ml(-1).

Promazine pharmacokinetics during concurrent treatment with tricyclic antidepressants

The aim of the present study was to search for a possible effect of tricyclic antidepressants on the pharmacokinetics of promazine. Male Wistar rats received promazine and/or an antidepressant (amitriptyline, imipramine) at a dose of 10 mg/kg i.p. twice a day for two weeks. Amitriptyline increased the plasma concentrations of promazine and N-desmethylpromazine. The concentration of promazine sulfoxide was lowered after 30 min, but later it was raised after 6 and 12 h. The interaction was pronounced after 6 and 12 h when the concentration of promazine was 3 times as high, that of N-desmethylpromazine 25 times as high, and that of sulfoxide 22 times as high as those observed after administration of promazine alone. Similar results were obtained in the brain. Imipramine produced less distinct changes in promazine pharmacokinetics. It did not produce any significant changes in promazine concentration (a tendency to raise it after 30 min was observed) in plasma, but it significantly increased the concentration of N-desmethylpromazine and decreased that of promazine sulfoxide. Changes in the brain did not follow closely those in the plasma. In the brain, significant increases in the levels of promazine and its metabolites were observed after 6 and 12 h. In vitro studies with liver microsomes showed that chronic co-administration of the antidepressants did not significantly influence the rate of promazine demethylation and sulfoxidation. Instead, the Lineweaver-Burk's analysis showed that both amitriptyline and imipramine competitively inhibited the two metabolic pathways of the neuroleptic. The potency of imipramine to inhibit the promazine metabolism in vitro was lower than that of amitriptyline, which was in line with its weaker effect on the pharmacokinetics of promazine in vivo. The observed increase in the sum of concentrations of the measured compounds (promazine + metabolites) in the plasma suggests additional inhibition by amitriptyline of another, metabolic pathway of promazine (e.g. hydroxylation). It is concluded that amitriptyline and imipramine which interfere with the metabolism (and probably distribution) of promazine produce potent increases in the brain (in the case of amitriptyline also in the plasma) concentrations of the neuroleptic.

Contribution of lysosomal trapping to the total tissue uptake of psychotropic drugs

The present study was aimed at assessing individual contributions of the phospholipid binding and lysosomal trapping to the total tissue uptake of psychotropic drugs with different chemical structures, such as promazine, imipramine, amitriptyline, fluoxetine, sertraline (basic lipophilic drugs) and carbamazepine (lipophilic, but not basic). We also tried to find out whether lysosomal trapping may be involved in the pharmacokinetic interactions in clinical combinations of psychotropics. Uptake experiments were carried out on slices of various rat tissues as a system with intact lysosomes. Initial concentration of each drug was 5 microM. The results were compared with those obtained in the presence of the "lysosomal inhibitors", ammonium chloride or monensin. The basic lipophilic psychotropics showed high uptake in tissues known for the abundance of lysosomes, mainly the lungs. The highest drug accumulation was found for promazine and amitriptyline. "Lysosomal inhibitors" significantly decreased the uptake of the basic lipophilic drugs, particularly in the lungs and liver. The most potent effect was observed for amitriptyline, imipramine and promazine. The brain showed moderate accumulation of basic lipophilic psychotropics and the effect of the "lysosomal inhibitors" was significant only in the case of amitriptyline, imipramine and sertraline. The only exception to the above regularity were imipramine and sertraline which were taken up more extensively by the adipose tissue than by lysosome-rich tissues such as the lungs or liver. Carbamazepine did not show lysosomotropism. Amitriptyline and promazine mutually decreased their uptake by lung slices when the drugs were incubated jointly. In the presence of ammonium chloride the interaction did not occur. In conclusion, the obtained results show that (1) the lysosomal trapping is an important factor determining the distribution of the basic lipophilic psychotropics; however (2) their tissue uptake depends more on the phospholipid binding than on the lysosomal trapping; (3) the lysosomal trapping may be involved in the pharmacokinetic interactions between psychotropics.

Effect of carbamazepine on the pharmacokinetics of promazine

Combinations of neuroleptics and carbamazepine are administered to psychiatric patients in the therapy of mania, manic-depressive illness and schizophrenia. The present study was aimed at assessing the influence of carbamazepine on the pharmacokinetics of promazine. Male Wistar rats received promazine and/or carbamazepine twice daily for two weeks (promazine, 10 mg/kg ip; carbamazepine, 15 mg/kg ip during the 1st, and 20 mg/kg ip during the 2nd week of treatment). In a short time (1 h) after administration, carbamazepine had a tendency to increase the concentration of promazine in the blood plasma and brain. Lineweaver-Burk's analysis showed that carbamazepine added in vitro competitively inhibited the N-demethylation of promazine in liver microsomes, without affecting the sulphoxidation process. The effect was reflected in vivo (1 h) by an increased promazine/desmethylpromazine ratio. After a long time interval (6 h, 12 h), carbamazepine decreased the concentration of promazine and its metabolites. In vitro studies into the promazine metabolism, conducted on microsomes from rats treated with promazine and/or carbamazepine, did not show acceleration of its demethylation or sulphoxidation by carbamazepine. The obtained results suggest that induction of promazine metabolism by carbamazepine involves metabolic pathways other than N-demethylation or sulphoxidation. It has been concluded that when a phenothiazine neuroleptic, such as promazine, is administered jointly with carbamazepine, a slight increase in the neuroleptic concentration may be expected in a short time after administration, followed by its significant decrease.

The pharmacokinetics of promazine and its metabolites after acute and chronic administration to rats--a comparison with the pharmacokinetics of imipramine

This study was aimed to investigate the pharmacokinetics of promazine (a phenothiazine analogue of imipramine) after its single and repeated administration. Male Wistar rats received promazine as a single injection (10 mg/kg ip) or they were treated chronically with the neuroleptic, once a day for two weeks. Plasma and brain concentration of promazine, desmethylpromazine and promazine sulphoxide were determined using the HPLC method devised by us. The results of the present study were compared with our earlier data obtained in analogous experiments with imipramine. The obtained data showed that the pharmacokinetics of promazine and imipramine was similar, though certain differences could be noticed. Both those drugs were unevenly distributed throughout the body, occurring in low concentrations in the blood plasma and reaching considerably higher concentrations in the brain. However, the uptake of promazine by the brain was more efficient than that of imipramine. The brain/plasma AUC ratio after a single dose amounted to 28.72 for promazine and 12.78 for imipramine. Their demethylated metabolites behaved in a similar way, where as the level of promazine sulphoxide in the brain was three times lower than that in the plasma. Chronic treatment with promazine or imipramine increased concentrations of the parent compounds and their demethylated metabolites, and prolonged their half-life in the plasma and brain. The plasma level of promazine sulphoxide did not change, and its brain level was decreased by chronic treatment with promazine. The half-life of promazine sulphoxide was prolonged in the plasma but shortened in the brain after repeated administration of promazine. The observed considerable amounts of desmethylpromazine and promazine sulphoxide, formed in vivo, suggest that the two compounds are major metabolites of promazine, and that the metabolic pattern of promazine in the rat and man is similar.

Pharmacokinetics of promazine in patients with hepatic cirrhosis--correlation with a novel galactose single point method

We examined promazine pharmacokinetics in nine patients with hepatic cirrhosis and in six healthy subjects. A specific and sensitive HPLC method was used to measure promazine concentrations in plasma, plasma water (free drug), red blood cells, and urine after oral administration of promazine (2 x 50 mg tablet). There were highly significant reductions in total plasma clearance (p < 0.01), free drug total plasma clearance (p < 0.01), metabolic clearance (p < 0.01), metabolic clearance of free drug (p < 0.01), and fraction bound (p < 0.01) in the cirrhotic patients. The elimination half-life and the area under the plasma concentration-time curve were significantly increased (p < 0.001 and p < 0.05, respectively) in the cirrhotic patients. However, the overall excreted promazine in urine, time to the promazine peak concentration, distribution half-life, renal clearance, apparent volume of distribution, and the promazine concentration ratio between plasma and red blood cells were not different. Thus caution is needed in using promazine for patients with hepatic cirrhosis. A newly developed galactose single point (GSP) method was applied to quantitatively measure the residual liver function in cirrhosis patients and successfully correlated it with promazine elimination half-life (r = 0.770, p < 0.01), total plasma clearance of free drug (r = 0.899, p < 0.005), metabolic clearance of free drug (r = 0.902, p < 0.005), and plasma protein binding (r = 0.822, p < 0.005). GSP may be a convenient index for promazine routine dosage adjustment in patients with liver cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Absolute bioavailability of chlorpromazine, promazine and promethazine]

The absolute bioavailability of the three phenothiazine neuroleptics, promazine (Sinophenin, CAS 58-40-2), chlorpromazine (Propaphenin, CAS 50-53-3) and promethazine (Prothazin, CAS 60-87-7) was tested in three single-dose cross-over studies. In each trial 12 to 14 healthy volunteers were enrolled. The single doses for promazine, promethazine and chlorpromazine were 100, 75 and 150 mg (orally) and 20, 50 and 50 mg (intravenously), resp. The serum concentrations of the three neuroleptics were measured by means of a selective HPLC-method. the distribution-free confidence intervals for the absolute bioavailability of the three phenothiazines were within 10.5 to 24.7% for chlorpromazine, 7.8 to 24.9% for promazine and 12.3 to 40% for promethazine. Promazine and chlorpromazine are pharmacokinetically very similar and differ substantially from promethazine.

Inhibition and induction of cytochrome P450 2B1 in rat liver by promazine and chlorpromazine

Phenothiazine tranquilizers have been associated with pharmacokinetic drug interactions in man. In this study the in vivo and in vitro effects of the clinically important phenothiazines promazine (PZ) and chlorpromazine (CPZ) on drug oxidations catalysed by specific cytochrome P450 (P450) enzymes were investigated in the rat. In vitro, the two drugs were relatively ineffective inhibitors of constitutive P450 activities, but were inhibitory toward the principal phenobarbital-inducible P450 2B1 and, to a lesser extent, P450 1A1. Administration of PZ and CPZ to male rats did not markedly influence the total microsomal P450 content of the liver. However, the quantitatively important male-specific P450 2C11 was down-regulated by CPZ and concomitant induction of P450 2B1 and associated 7-pentylresorufin O-depentylase activity were noted. A small increase in the activity of microsomal 7-ethylresorufin O-deethylase was also observed following administration of both drugs to rats, suggesting induction of P450 1A1/2. Considered together, it is apparent that the two phenothiazines are preferential inhibitors and inducers of P450 2B1 in rat liver. Drug interactions in humans involving phenothiazines may reflect a combined effect of induction and inhibition processes as well as down-regulation of other P450s, such as that produced by CPZ on P450 2C11.

Pharmacokinetics of promazine: I. Disposition in patients with acute viral hepatitis B

Concentrations of promazine in plasma, plasma water, red blood cells, and urine were measured after oral administration of the drug to six patients during and after apparent recovery from the acute phase of viral hepatitis B. None of the promazine pharmacokinetic parameters were significantly different during and after the acute phase; these parameters included clearance, free drug clearance, metabolic clearance, volume of distribution, distribution and elimination half-life values, plasma protein binding, and per cent excreted in the urine. During the acute period of the illness, SGOP, SGPT, alkaline phosphatase, and total bilirubin were increased in all patients; they returned to within or near the upper limits or normal after recovery. Despite the unchanged promazine disposition, four out of six patients had more severe promazine side-effects, such as sedation, postural hypotension, and dizziness during the acute phase of the illness. This study suggests that promazine disposition was not significantly altered as a consequence of viral hepatitis. However, the pharmacodynamic effects of promazine were changed significantly. Care must be taken with patients who are taking promazine during the acute phase of viral hepatitis B.

Stability, human blood distribution and rat tissue localization of promazine and desmonomethylpromazine

The stability in human blood and urine, partitioning into red blood cells and plasma protein binding of promazine and desmonomethylpromazine were investigated. Tissue localization was investigated in rats. Promazine and desmonomethylpromazine were stable in human plasma and urine for at least 64 days at -20 degrees. The percentage of promazine not bound to protein in plasma was 10.4 +/- 2.43 as estimated by equilibrium dialysis with correction for volume shift, and 11.6 +/- 0.43 per cent as estimated by ultracentrifugation. Data for the mean plasma/red blood cell concentration ratio and the red blood cell/plasma distribution coefficient for promazine were 1.19 +/- 0.13 and 8.21 +/- 0.40, respectively. There was no evidence of time-dependence in plasma/red blood cell partitioning. Ten rat organs and tissues were examined. The concentrations of promazine and desmonemethylpromazine were highest in lung. For promazine, the rank order of tissue localization was lung greater than liver greater than kidney greater than intestine greater than brain greater than spleen greater than red blood cell greater than voluntary muscle greater than plasma greater than stomach greater than heart. For desmonomethylpromazine, the order was reversed in the cases of spleen and brain and interchanged in the cases of stomach and muscle. The brain/plasma concentration ratios for promazine and desmonomethylpromazine in rat were 4.69 and 3.87, respectively.

Metabolism and pharmacokinetic studies of propionylpromazine in horses

The propionylpromazine concentrations in plasma after intramuscular administration to horses were determined using gas chromatography with nitrogen-phosphorus detection. After hydrolysis by beta-glucuronidase/arylsulphatase, the parent drug and three metabolites were detected in urine. The metabolites were identified as 2-(1-hydroxypropyl)promazine, 2-(1-propenyl)promazine and 7-hydroxypropionylpromazine by gas chromatography-mass spectrometry. No N-demethylated or sulphoxidated metabolites of propionylpromazine were observed in the horse urine.

Thin-layer chromatographic screening method for the tranquillizers azaperone, propiopromazine and carazolol in pig tissues

A procedure is described for the detection of azaperone, propiopromazine and carazolol in pig muscle, liver and kidney tissue. The method comprises extraction from an alkaline tissue homogenate with diethyl ether, followed by cleaning up and concentration of the extract on a silica gel solid-phase extraction column. Two-dimensional thin-layer chromatography on a silica plate was used for the detection of the tranquillizers. Detection levels were 25 micrograms kg-1 for propiopromazine, 50 micrograms kg-1 for azaperone (or its metabolite azaperol) and 125 micrograms kg-1 for carazolol. In pigs treated with the usual doses the presence of propiopromazine and azaperol could be established in kidney tissue 8 h after administration, whilst in injection sites all three tranquillizers could be detected.

In vitro inhibition of human platelet monoamine oxidase by phenothiazine derivatives

Nineteen phenothiazines were tested for in vitro inhibition of human platelet type B monoamine oxidase (MAO). The inhibition potency was highly dependent on structures of their side chains. The inhibition was most potent for drugs with (hydroxyethyl-piperazinyl)propyl chains followed in decreasing order by those with (N-methylpiperazinyl)propyl, (2-dimethylamino-2-methyl)ethyl and 3-dimethylaminopropyl chains. Kinetic analyses were carried out for promazine, promethazine, perazine and perphenazine as representatives of each group; the four drugs showed competitive inhibition, and Ki values of 124, 31.4, 19.2 and 22.6 microM, respectively.