A simple and sensitive radioreceptor assay for antischizophrenic drugs in blood

In vivo potencies of antipsychotic drugs in blocking alpha 1 noradrenergic and dopamine D2 receptors: implications for drug mechanisms of action

In addition to being dopamine antagonists, all antipsychotic drugs are potent antagonists of alpha-1 noradrenergic receptors. Nevertheless, the contribution of alpha blockade to the clinical therapeutic effects of the antipsychotic drugs has never attracted extensive study. In particular, the relative alpha-1 noradrenergic antagonist potency of antipsychotic drugs has rarely been determined in vivo during extended treatment, although such treatment would provide a better model of clinical drug effects than the determination of potencies in in vitro systems, such as assays of competition for binding sites in tissue homogenates, as is most often done. To estimate the physiological efficacy of antipsychotic drugs as dopamine and alpha adrenergic antagonists, we treated rats for four weeks with daily IP injections of the following antipsychotic drugs: Fluphenazine, 1 mg/kg; haloperidol, 1 mg/kg; chlorpromazine, 25 mg/kg; thioridazine, 25 mg/kg; and clozapine, 25 mg/kg. Effective antagonism should lead to an increase in density of the relevant receptors. After two drug-free days, rats were sacrificed and the affinity and density of dopamine D2 and alpha-1 noradrenergic receptors were determined in striatum and brain exclusive of striatum, respectively. Alpha 1 noradrenergic receptor density but not dopamine receptor density was increased after all treatments. Thus, preliminary experiments with this in vivo model suggest that all antipsychotic drugs are effective antagonists at alpha 1 noradrenergic receptors, while not all are effective antagonists at dopamine D2 receptors.

Down regulation of beta-receptors by bupropion and its major metabolite in mouse brain

Mice were treated with bupropion Compound II (major metabolite of bupropion) or desmethylimpramine (DMI) twice a day intraperitoneally for either 1 or 3 weeks. The binding of dihydroalprenolol and spiroperidol in the frontal cortex and limbic forebrain areas were analyzed. There was a significant reduction in beta-receptors in the frontal cortex induced by DMI at both times examined. Bupropion showed a significant reduction of beta-receptor in the frontal cortex by 3 weeks. Though propiophenone did not have any significant effect on beta-receptors in the frontal cortex, it down-regulated beta-receptors in the limbic forebrain area significantly by 1 and 3 weeks. There was no significant effect of buropion or propiophenone on the binding of spiroperidol either in the cortex (S2 receptor) or in the limbic forebrain (dopaminergic). These results show that bupropion may exert part of its clinical effect through its metabolite propiophenone.

Neuroleptic bioavailability, psychosocial factors, and clinical status: a 1-year study of schizophrenic outpatients after dose reduction

Serum neuroleptic levels, prolactin levels, and clinical state were assessed for 1 year in 29 schizophrenic outpatients whose clinically determined neuroleptic dose had been reduced by 50%. Fifty-five percent of the subjects remained stable. Neuroleptic dose did not differ between relapsed and stable patients. Serum prolactin (PRL) assessed 2 weeks after dose reduction and mean PRL after reduction were significantly lower among relapsers. Serum neuroleptic levels were significantly lower for relapsers in patients on haloperidol. Among relapsers, there were no serum PRL or neuroleptic level differences between stable periods and the relapse episode. Among patients with relatively low neuroleptic bioavailability, relapsers reported lower levels of social activity and had social networks that were less enjoyable, more aversive, and less helpful than those of stable patients.

Hypophysectomy may non-selectively alter pharmacokinetic parameters to enhance the ability of haloperidol to increase striatal dopamine receptor density in the rat

We have investigated the effect of a range of doses of haloperidol (0.625-5.0 mg/kg/day) or saline, administered for 14 days, followed by a 3 day drug washout period, to sham operated or hypophysectomized rats. Haloperidol increased the number of specific striatal 3H-spiperone binding sites (Bmax) in sham-operated animals at doses of 2.5 and 5.0 mg/kg/day, and in hypophysectomized animals at all doses used (0.625-5.0 mg/kg/day). The inhibition of locomotor activity produced by haloperidol was greater in hypophysectomized than sham-operated animals. Plasma and striatal haloperidol levels after equivalent doses were greater in hypophysectomized than in sham-operated animals. We conclude that hypophysectomy may enhance the ability of haloperidol to induce striatal dopamine receptor supersensitivity in the rat, and that this may be due to differences in the pharmacokinetic handling of haloperidol between sham-operated and hypophysectomized animals.

Possible associations among plasma prolactin levels, tardive dyskinesia, and paranoia in treated male schizophrenics

To determine whether there is an association between prolactin (PRL) levels and psychopathology or tardive dyskinesia during neuroleptic treatment, we measured plasma prolactin levels and neuroleptic activity (NA) in 33 chronically treated male schizophrenics. Neuroleptic dose, plasma NA, and PRL were significantly intercorrelated. Plasma PRL levels were also measured in 8 male schizophrenics recently withdrawn from neuroleptics and in 18 normal male controls. In treated patients, but not in controls, PRL levels decreased with age and duration of illness, two variables that we interpreted as indirect measures of neuroleptic exposure. PRL levels in patients recently withdrawn from neuroleptics were lower than in treated patients or controls, which was suggestive of rebound hypoprolactinemia. A prolactin index, calculated as the ratio of PRL levels to NA, was inversely correlated with paranoid symptoms and tardive dyskinesia in younger treated patients. These results lead to speculation that tuberoinfundibular dopaminergic supersensitivity develops in chronically treated schizophrenics and that it is associated with nigrostriatal supersensitivity, manifested by tardive dyskinesia, and paranoid symptoms, which may reflect mesolimbic supersensitivity.

Determination of chlorpromazine in serum by radioreceptor assay and HPLC

A radioreceptor assay for chlorpromazine in serum, which is based on binding to dopamine receptors, is described. This method has been postulated to measure all active metabolites as well as the parent drug. We have compared this method with an HPLC method for chlorpromazine. Dopamine-blocking activity, measured in serum samples from schizophrenic patients receiving chlorpromazine, was 1.85-9.1 times higher than serum chlorpromazine level measured by HPLC. The correlation between the two methods was 0.75. Dopamine-blocking activity was related more closely to dose of drug and to serum prolactin level than was serum chlorpromazine level measured by HPLC.

Radio receptor assay of serum neuroleptic levels in psychiatric patients

The radioreceptor assay for the measurement of neuroleptic drugs in serum has been used to study the relationship between dose and serum level in schizophrenic patients receiving these drugs. The assay was found to be reproducible and capable of detecting neuroleptics in the sera of patients receiving a range of both oral and depot drugs, with the exception of trifluoperazine spansules. Linear correlations were obtained between daily dose and serum level for each drug both in individual patients on different doses and between patients on a stable dose. Extrapyramidal side effects were related to the serum neuroleptic level within, but not between, patients. The assay may be of use in clinical practice, including the assessment of compliance or poor response to neuroleptics.

Serum levels and clinical response in long-term pharmacotherapy with zuclopenthixol decanoate

Twenty-six patients diagnosed as chronic schizophrenics were given injections of zuclopenthixol decanoate (cis(Z)-clopenthixol decanoate) 200 mg every 3 weeks for at least 6 months. Before treatment and on each day of injection the patients' mental state was assessed by Brief Psychiatric Rating Scale (BPRS), 18 items. A registration of side effects and basal laboratory data was also performed. Blood samples were drawn on each day of injection before injection and 3-7 days after injection (time of maximum concentration). Neuroleptic activity, which was considered equivalent to the concentration of zuclopenthixol, was determined in serum by radio-receptor assay (RRA). Based on amelioration scores greater than or equal to 50% on the BPRS, 15 patients were characterized as responders and 11 as non-responders. The responder group showed a statistically significant reduction in BPRS score, whereas this was not the case for the non-responders. Apart from a few patients, the serum concentrations showed a low intra-individual variation, but a relatively high inter-individual variation. The responder group had a significantly higher mean pre-injection concentration than the non-responder group, whereas no significant difference was found in day 3-7 concentrations. The fluctuation of the serum concentration expressed as the ratio between maximum (days 3-7) and minimum (pre-inj.) was found to be significantly lower for responders than for non-responders. Thus although the present study did not demonstrate a clear relationship between serum level and clinical effect, it indicates that the best antipsychotic effect is obtained with a serum concentration which fluctuates only slightly (the ratio max/min concentration not exceeding 2.1).

Plasma level monitoring of antipsychotic drugs. Clinical utility

The steady-state plasma concentrations of antipsychotic drugs show large interpatient variations but remain relatively stable from day to day in each individual patient. Monitoring of antipsychotic drug concentrations in plasma might be of value provided the patients are treated with only 1 antipsychotic drug. Some studies have reported a relationship between therapeutic response and serum antipsychotic drug 'concentrations' as measured using the radioreceptor assay (RRA) method, which measures dopamine receptor-blocking activity in plasma. Most studies, however, have failed to demonstrate such a relationship, and the RRA does not seem to provide the generally useful tool for plasma concentration monitoring of antipsychotic drugs that was hoped for initially. A lack of correlation between dopamine receptor-blocking activity in plasma and therapeutic response may be due to differences in the blood-brain distribution of both antipsychotic drugs and their active metabolites. Chemical assay methods (e.g. GLC and HPLC) have been used in studies which examined the relationships between therapeutic response and antipsychotic drug concentrations in red blood cells and in plasma. It seems that for these drugs, measuring red blood cell concentrations does not offer any significant advantage over measuring plasma concentrations. Reasonably controlled studies of plasma concentration-response relationships using randomly allocated, fixed dosages of chlorpromazine, fluphenazine, haloperidol, perphenazine, sulpiride, thioridazine and thiothixene have been published but often involve relatively few patients. A correlation between therapeutic response and plasma concentrations of thioridazine and its metabolites has not been demonstrated, and plasma level monitoring of thioridazine and its metabolites therefore appears to have no clinical value. Clinical behavioural deterioration concomitant with high plasma concentrations of chlorpromazine and haloperidol have been reported. A dosage reduction might be considered after 2 to 4 weeks' treatment in non-responders who have plasma chlorpromazine concentrations above 100 to 150 micrograms/L or plasma haloperidol concentrations above 20 to 30 micrograms/L. Non-responders and good responders to chlorpromazine treatment, however, have plasma drug concentrations in the same range, and a therapeutic range of plasma chlorpromazine levels has not been defined. Therapeutic plasma haloperidol concentrations (i.e. 'window') in the range of 5 to 20 micrograms/L have been reported by some investigators, but others have found no such relationship.(ABSTRACT TRUNCATED AT 400 WORDS)

Therapeutic monitoring of psychotherapeutic drugs: role of the clinical laboratory

Therapeutic monitoring of drugs is a well established clinical tool. However, the state of the art is somewhat less advanced for drugs used in psychiatry than it is for other classes of drugs, for several reasons. Most psychotherapeutic drugs have large volumes of distribution and achieve relatively low plasma concentrations following therapeutic doses. Many have one or more active metabolites. While psychotherapeutic drugs act through biochemical mechanisms, they are used to treat clinical syndromes which may be heterogeneous in their biochemical pathogenesis. As a consequence, the analytical methodologies are often complex and not always reliable; well-controlled clinical studies are difficult to perform; the therapeutic ranges have been difficult to establish. Despite these limitations, prudent and selective monitoring of serum drug concentrations, particularly of the tricyclic antidepressants, can be helpful in clinical management.

Analysis of tricyclic antidepressant drugs in plasma and serum by chromatographic techniques

A review of methods for the determination of tricyclic antidepressants in plasma or serum, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of their precision, accuracy, sensitivity and selectivity, with respect to parent drug and metabolites, is used to facilitate a comparison of methods. No one technique can be claimed as the method of choice for these drugs, although gas-liquid chromatography with nitrogen selective detection has some strong claims, viz. generally good sensitivity and reproducibility of assays and ready availability of equipment in most laboratories. The ultimate choice of a method for determining tricyclics will be determined more by the clinical application (routine monitoring versus pharmacokinetics) than by other factors.

Neuroleptic serum levels measured by radioreceptor assay in patients receiving intramuscular depot neuroleptics. Some preliminary findings

Twenty-six chronic schizophrenic patients on well established depot neuroleptic regimes with stable doses (16 on fluphenazine decanoate, ten on flupenthixol decanoate) had serum neuroleptic levels measured by a radioreceptor assay (RRA) method. The assay was sufficiently sensitive to measure serum levels in all cases, with acceptable levels of inter-assay variation. Blood level measurements were repeated on two occasions, at the same time interval from the last injection, in 18 patients (11 on fluphenazine decanoate, seven on flupenthixol decanoate) and remained reasonably stable in most cases, although others showed a wider variation. Despite a wide range of doses (X 32 fluphenazine decanoate, X 21 flupenthixol decanoate) the serum levels fell in a remarkably narrow range (X 4, X 6). There was a significant correlation between dose and blood level for flupenthixol decanoate, but not for fluphenazine decanoate.

The assessment of a psychosocial treatment with chronic schizophrenic patients using neuropsychopharmacological indices

The current investigation explored and compared the genotypic neuropsychopharmacological indices of eight chronic schizophrenic patients and four therapists on an inductive paradigm. Patients and normals were screened with clinical interviews, psychometric and psychophysiological tests and neuroleptic availability radioreceptor assays were monitored within a three month pre-post treatment design. Results revealed that clinical, psychometric and psychophysiological parameters failed to reach statistical significance in a three month pre-post treatment structure and functional comparison. The implications for future schizophrenia research are discussed and illustrated using actual neuropsychophysiological phenotypic and genotypic profiles of introverted, extroverted and ambivert schizophrenic patients.

Total and free plasma neuroleptic levels in schizophrenic patients

Nineteen male patients, under 35 years of age, newly admitted with a diagnosis of schizophrenia, were treated with either chlorpromazine or haloperidol at a fixed dosage for 25 days. Both total and free plasma neuroleptic levels were measured using a radioreceptor assay. Clinical response was measured by the Brief Psychiatric Rating Scale (BPRS). On day 25, nonresponders (those with a decrease of less than 8 points on the BPRS) had both total and free plasma neuroleptic levels within the range observed in responders. It is therefore concluded that lack of therapeutic response is generally not due to inadequate plasma drug levels.

Determination of benperidol in human plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the quantitative determination of benperidol in human plasma using haloperidol as internal standard is described. The method involves liquid-liquid extraction, separation of the substances on a reversed-phase column C18 followed by ultraviolet detection at 254 nm. The mobile phase consists of 32% acetonitrile in 0.05 M potassium dihydrogen phosphate buffer (pH 2.8). The detection limit is 0.5-1.0 ng/ml using 2- or 4-ml plasma samples.

Increased sensitivity of rabbit carotid body chemoreceptors to dopamine after chronic treatment with domperidone

An increase in specific dopamine D2 receptor binding sites was observed in membranes prepared from the carotid bodies of rabbits treated for 8 weeks and then withdrawn for 4-9 days from the D2 antagonist domperidone (2-5 mg/kg per day). Recordings of chemoreceptor afferent discharge from the carotid body also revealed that this change in receptor density was accompanied by an increased sensitivity to the chemodepressant effects of exogenous dopamine. The chemoreceptor responsiveness of the carotid body to hypoxia is blunted in rabbits treated chronically with domperidone, but this can be restored to normal by an acute dose of the D2 antagonist. These experiments provide evidence that is compatible with a chemo-inhibitory role for endogenous dopamine in the rabbit's carotid body. Furthermore, these results suggest that the carotid body provides a useful model for the functional studies of dopamine D2 receptors.

The Genain Quadruplets 25 years later: a diagnostic and biochemical followup

A biological and clinical followup of the Genain Quadruplets was initiated as a multilaboratory collaborative effort at the National Institute of Mental Health (NIMH). The quadruplets are 51-year-old monozygotic women previously studied with a battery of psychological and physiological tests 25 years ago at the NIMH. The present article (the first of a series of three) details the clinical history and course of the schizophrenic illness in each of the quadruplets and describes the biochemical measures determined. The findings of elevated urinary phenylethylamine excretion, decreased plasma dopamine-beta-hydroxylase activity, and increased alpha-adrenergic receptor concentrations in all quadruplets warrant further genetic studies.

In vitro interaction of neuroleptics and tricylic antidepressants with coffee, tea, and gallotannic acid

The in vitro interaction of selected drugs with coffee, tea, gallic acid, and gallotannic acid was examined by mixing solutions of drug with each of these four preparations. Results of these experiments indicate that significant precipitation occurs for a variety of agents, including several phenothiazines, amitriptyline, haloperidol, imipramine, and loxapine. The strong complex which is formed between these drugs and tannins is probably the basis of the interaction of these drugs with coffee and tea. Although precipitates did occur with a number of neuroleptics, two members of this drug class, thiothixene and molindone, failed to interact with the solutions used.

Radioreceptor assay for ergot derivatives, transdihydrolisuride and lisuride, in biological fluids

The development of a sensitive radioreceptor assay (RRA) for transdihydrolisuride (TDHL) and lisuride, as well as the synthesis of tritiated TDHL, is described. The method is based upon the competition between 3H TDHL and TDHL or lisuride for rat brain dopaminergic receptors. Linear calibration graphs were obtained in the range of 0.2-9 pmol for an ergot derivative. Relative affinities of the main metabolites, deethylated and dideethylated on the urea part of the molecule are 3.6% and 1.5%, respectively, as compared to the parent drug. To verify the method, plasma levels of TDHL were determined in rats after oral administration.

Plasma kinetics of dihydroergotoxin in rat by using a radioreceptor assay

A radioreceptor assay (RRA) (with brain dopamine receptors) has been developed to determine the levels of dihydroergotoxin-equivalent (DHT-equivalent) material in rat plasma and its kinetics after oral and i.v. administration (5 mg/kg). After i.v. administration the plasma kinetics follows a two-exponential equation, with an apparent distribution volume of 7-9 1/kg and a long half-life (about 36 hours). The kinetics of DHT after oral administration shows two peaks; this could indicate a biliary recycling of the drug and/or of its metabolites. The low bioavailability (19%) and the biliary recycling of DHT-equivalent material suggest a first pass effect.

Selection of analytic methods for therapeutic drug monitoring

Selection of an analytic method for therapeutic drug monitoring usually involves an initial choice between chromatography and immunoassay. Once this decision has been made, numerous options remain within these two broad categories. There is no single correct or preferred assay technique. The best decision, based on technical, clinical, and economic considerations, will vary in different clinical and laboratory environments. The laboratory that has sufficient resources to maintain more than one type of technology will have a greater degree of flexibility in solving special problems.

Simple radioligand binding assay for the determination of urinary scopolamine

A sensitive radioligand binding assay is described for the determination of scopolamine in human urine. As a measure for the drug concentration, the quantitative displacement of scopolamine of tritiated quinuclidinyl benzylate from rat brain receptors was used. The assay is sensitive to concentrations as low as 1.2 ng/mL, surpassed only by GC-MS techniques. It can be performed easily and quickly and does not include extraction procedures. Scopoline and scopine , possible metabolites of scopolamine, do not interfere with the assay. After transdermal administration of scopolamine, 34% of the drug is found in the urine. Of the total scopolamine excreted, 79% is conjugated to glucuronic and/or sulfuric acid and 21% is excreted in the unbound form.

Serum effects confound the neuroleptic radioreceptor assay

The neuroleptic radioreceptor assay (NRRA) is used widely to monitor total neuroleptic-like activity (NLA) in patients taking one or more antipsychotic drugs. The original report of Creese and Snyder (1) stated that serum alone caused a small effect on binding which was negligible compared to normal daily variations in the assay. Conversely, in studies with striata from rat or cow brain, we found that sera from healthy, drug free volunteers, when used at 50 microL/1 mL assay volume, caused marked inhibition of binding. Although any sample of serum causes reproducible inhibition with a given preparation of bovine or rat striatal membranes, the effects of various serum samples may differ markedly when several striatal membrane preparations are compared. Moreover, samples taken from people at different times may also vary, although less than the interindividual differences. Despite this variance, the slopes of log-logit plots were equal to 1 either in the presence or absence of serum. Because of the differences in the interaction of individual sera with different membrane preparations, it is difficult to compensate accurately for this serum effect by simply including control serum in the standard curve. Thus, the use of the NRRA as a quantitative tool in the clinical pharmacology of neuroleptics may be limited by this non-specific effect of serum, and this finding may offer one explanation for some of the inconsistencies found in comparing the NRRA with direct analytical methods.

The relationship of dopamine receptor blockade to clinical response in schizophrenic patients treated with pimozide or haloperidol

Pimozide and haloperidol were found to be equally effective in the treatment of acute schizophrenia in a double-blind clinical trial involving 22 patients. Drug plasma levels measured by radioimmunoassay (RIA) did not correlate with clinical response following either drug. Nor was there any correlation between clinical response and the dopamine receptor blocking activity of either drug as measured by radio receptor assay (RRA). Following pimozide plasma prolactin (PRL) levels correlated with clinical change, although the time courses of response of PRL and clinical response were dissimilar. There was no correlation between PRL and clinical response to haloperidol. RRA and RIA values correlated highly following pimozide but not haloperidol. Our findings lead us to conclude that the RRA technique reflects the plasma level of a drug rather than its central dopamine blocking activity. We also consider that the clinical response to antipsychotic drugs in schizophrenia may be less directly linked to dopamine receptor blockade than has previously been supposed.

Serum neuroleptic concentrations and clinical response: a radioreceptor assay investigation of acutely psychotic patients

Twenty-two acutely psychotic patients were rigorously assessed for psychopathology at baseline and after 14 days of neuroleptic treatment. The neuroleptic radioreceptor assay (NRRA) was used to determine serum neuroleptic concentrations. Serum neuroleptic concentration was significantly, nonlinearly related to changes in BPRS Total Score, and BPRS Factor Scores for Thought Disturbance and Anxiety-Depression. Clinical improvement was associated with intermediate (11-50, 51-126 ng/ml haloperidol equivalents) while poor clinical outcome was related to both low (less than or equal to 10 ng/ml) or high (greater than 125 ng/ml) serum levels. The results are discussed in terms of a possible "therapeutic window" for the neuroleptics and the implications this might have for clinical practice.

Neurotransmitters and receptors: clinical implications

With the advent of new techniques such as the radioreceptor binding assay, significant advances have been made in the field of psychopharmacology during the past seven years. In this paper we discuss some of these contributions regarding our understanding about the nature of different psychopathological conditions such as anxiety, depression and schizophrenia.

Reduced haloperidol: effects on striatal dopamine metabolism and conversion to haloperidol in the rat

Acute injection of rats with either haloperidol or reduced haloperidol (1 mg/kg, IP) greatly increased the striatal concentrations of the acidic dopamine metabolites, indicating enhanced turnover of dopamine. The effect of reduced haloperidol was almost as great as that of haloperidol. Reduced haloperidol, however, was much less efficient (about 400 times) than haloperidol in displacing [3H]spiperone binding to striatal membranes in vitro. In agreement with the above results, reduced haloperidol was found to be oxidized to haloperidol, so that 2 h after injection of reduced haloperidol the concentrations of haloperidol and reduced haloperidol were equal in the striatum. The apparent conversion of reduced haloperidol to haloperidol was much quicker in liver than in plasma or brain, and it is suggested that the conversion primarily occurs in the liver. Before drawing any definite conclusion about the possible central activity of reduced haloperidol, further studies with other animal species are needed.

Prolactin response to single and multiple doses of haloperidol in schizophrenic patients

Serum prolactin and blood levels of haloperidol were assessed in schizophrenic patients after single acute oral doses of haloperidol and during fixed dose treatment with this medication. Although significant intrapatient correlations between prolactin responses to different doses of haloperidol were found, no statistically significant interpatient relationship between haloperidol dose and prolactin response emerged. There were statistically significant relationships between steady-state plasma and red cell haloperidol levels (measured by radioreceptor or gas liquid chromatographic techniques) and serum prolactin response, but not between blood levels after the acute haloperidol dose and prolactin response.

Pharmacokinetic and clinical studies with a benzodiazepine radioreceptor assay

Since the presence of benzodiazepine (BD) receptors was demonstrated in mammalian brain tissue, simple, sensitive and rapid techniques have been established to use BD-receptor preparations for specific radioreceptor assays (RRA). The RRA allows in vitro estimations of receptor affinity and concentration of BD in biological material, e.g. the time course of total BD binding activity in plasma (parent compound and active metabolites) may be evaluated. Several studies in volunteers with short and long-acting BD used as sedatives and hypnotics including diazepam (DZP), flunitrazepam (FNZ), flurazepam (FZP), lormetazepam (LMZ), oxazepam, temazepam and triazolam indicate that pharmacokinetic data (e.g. elimination half-lives of receptor active compounds) concur with the results obtained from other methods, if active metabolites are taken into account. For the evaluation of BD long-term and hangover effects in two placebo controlled double-blind studies (placebo vs. 1 mg and 2 mg LMZ, 2 mg FNZ, 30 mg FZP, 10 mg DZP) BD-binding equivalents and pharmaco-EEG recordings, subjective state, psychomotor as well as cognitive function were determined by standardized methods up to 154 hours following drug administration. Compared to placebo a distinct long-lasting increase in the relative power in beta-frequencies (12.5-30 Hz) and an impairment of psychomotor performance could be evidenced up to 12 h following FNZ and FZP intake. These effects correspond to the BD-binding activity in plasma. These findings indicate that BD-receptor preparations as used for the RRA are valuable tools to investigate binding affinities and pharmacokinetic properties of BD. Plasma levels of RRA active material may reflect a better correspondence to some clinical effects of BD than levels of the parent compound alone.

An early phase II clinical trial of BW234U in the treatment of acute schizophrenia in newly admitted patients

Sixteen schizophrenic patients, who were newly admitted to hospital from the emergency room, underwent a 3-6-day washout before being treated for 4 weeks with BW234U, a dimethylpiperazinyl-propylcarbazole derivative. Eight patients showed moderate to marked improvement in schizophrenic symptoms and there was a statistically significant (P less than 0.001) reduction in the mean score for Clinical Global Impressions in all patients. Four patients did not complete the trial; two because of poor therapeutic effect, one because of a grand-mal seizure and one because of an episode of loss of consciousness of unknown origin. BW234U showed no evidence of neuroleptic plasma activity (as measured by radioreceptor assay), did not induce plasma prolactin elevation and did not appear to cause parkinsonism.

Simple and reliable radioreceptor assay for beta-adrenoceptor antagonists and active metabolites in native human plasma

A radioreceptor assay (RRA) for the assay of beta-adrenoceptor antagonists in native human plasma is described. The hydrophilic antagonist 3H-CGP 12177 was used as the radioligand. In contrast to the hydrophobic radioligand 3H-dihydroalprenolol, which was investigated in parallel, the beta-adrenoceptor binding of 3H-CGP 12177 by rat reticulocyte membranes was found not to be affected by inclusion of increasing proportions (0-66% of incubation volume) of human plasma in the assay. Thus, solvent extraction of drug and/or active metabolites was not necessary to avoid binding of the radioligand tracer to plasma added in the RRA. The assay of unprocessed samples was possible. Drug concentrations in plasma after oral administration of propranolol (240 mg) or carteolol (30 mg) to 6 healthy volunteers were measured by the RRA and in parallel by a chemical method. The results from both methods agreed when the plasma concentration kinetics of propranolol were investigated (elimination half-life:3.9 h). In contrast, plasma concentrations of carteolol were consistently higher according to the RRA after oral administration of the drug. Identical concentrations, however, were found by the RRA and chemical method using plasma samples spiked with carteolol. Plasma concentrations of carteolol detected by the chemical method decline monoexponentially (elimination half-life: 5.4 h). A similar half-life of elimination for parent drug was found by the RRA (5.9 h), but an additional term describing the appearance of an active metabolite was necessary to account for the biphasic drug elimination (elimination half-life of metabolite: 17.3 h).(ABSTRACT TRUNCATED AT 250 WORDS)

A simple sensitive radioreceptor assay for calcium antagonist drugs

A radioreceptor assay for calcium channel antagonist drugs described here is based on the ability of these drugs to affect 3H-nitrendipine binding to calcium channels. All the known calcium channel antagonists may be assayed in this manner. The assay can detect 10-100 nM (4 - 40 ng/ml) nimodipine, 10-100 nM (3.5 - 35 ng/ml) nifedipine, 3-30 microM (1.2 - 12 micrograms/ml) prenylamine, 0.1 - 1.0 microM (49 - 490 ng/ml) verapamil and 3-30 microM (1.2 - 12 micrograms/ml) diltiazem. These values cover the range of concentrations of calcium channel antagonists that are clinically important. As the radioreceptor assay detects active metabolites as well as the parent drugs, it should prove a useful adjunct in cardiovascular therapy. The method is more reproducible, simpler and less expensive than other methods such as high pressure liquid chromatography.

Comparison between radioreceptor assay and radioimmunoassay for the determination of dihydroergotoxine in rabbit plasma samples

Two analytical methods, radioreceptor assay and radioimmunoassay, for the determination of dihydroergotoxine have been developed. Antiserum, providing sufficient sensitivity for the radioimmunoassay, was produced by immunizing rabbits with D-lysergic acid coupled to bovine serum albumin. Radioreceptor assay utilizing dopamine receptor was carried out to determine dihydroergotoxine and its pharmacologically active metabolites in rabbit plasma, and the result was compared with that obtained by radioimmunoassay. The values obtained in both assays were almost identical; it was, therefore, assumed that the plasma concentrations of dihydroergotoxine determined by the present radioimmunoassay reflects the amount of unchanged drug and its active metabolites.

The measurement of free nitrendipine in human serum by an equilibrium dialysis - radioreceptor assay

A radioreceptor assay using [3H]nitrendipine and rat cerebral cortical membranes, in conjunction with equilibrium dialysis, measures the unbound (free) level of nitrendipine in human sera. The sensitivity of the assay is 0.1-0.2 picomoles/ml and is linear from 4 X 10(-11) to 4 X 10(-9) M nitrendipine. Other dihydropyridine calcium channel antagonists may be measured using this assay if these compounds are used to generate the standard curve. Blank serum interferes with specific [3H]nitrendipine binding (24 percent inhibition per 20 microliter serum) whereas serum dialysates do not. Total serum nitrendipine levels may be measured, but the sensitivity of the assay is decreased due to interference by serum. Nitrendipine is highly protein bound in serum (93 - 99 percent). This protein binding is essentially unchanged over a serum concentration from 1 to 100 ng/ml. This assay is suitable for pharmacokinetic and pharmacodynamic studies.

Serum neuroleptic and prolactin levels in schizophrenic patients and clinical response

Following a drug-free placebo period lasting at least 1 week, 10 female and 11 male newly hospitalized schizophrenic patients received chlorpromazine (CPZ) 200 mg/day for 1 week and 400 mg/day the following week. Serum CPZ equivalent (CPZ-E) levels were measured at the end of each week of CPZ treatment with a radioreceptor assay. Chlorpromazine-E levels were significantly higher in females than males, but this finding could be accounted for by differences in body weight. Serum prolactin (PRL) levels were also higher in females than males. After differences in serum CPZ-E level were adjusted for, females still had significantly higher serum PRL levels than males. Serum PRL levels increased between the first and second treatment weeks in females but not in males. Correlations between serum CPZ-E and PRL levels were higher among males than females. Significant improvement for the patient group as a whole was observed during the 2 weeks of treatment, with a strong trend for females to improve more than males. Clinical outcome at this initial period was not predicted by either serum PRL levels or serum CPZ-E levels.

Radioreceptor and high-performance liquid chromatographic assays for the calcium channel antagonist nitrendipine in serum

Radioreceptor and high-performance liquid chromatographic (HPLC) assays for nitrendipine were developed and applied to the analysis of serum samples. The HPLC assay required both extraction and concentration of the serum samples, whereas the radioreceptor assay involved only direct dilution of the serum. The HPLC assay, in contrast to the radioreceptor assay, can be used for detection and quantitative analysis of biologically inactive metabolites. The radioreceptor assay is based on the competition between nitrendipine in serum and [3H]nitrendipine for high-affinity binding sites on cardiac membranes. Forty-two serum samples were obtained from five volunteers, and the HPLC and radioreceptor assay results were compared. A correlation coefficient of 0.98 was found between the results of the two assays within the nitrendipine serum concentration range of 1 to 20 ng/ml. No significant levels of active metabolites or any other interferences were found. The radioreceptor assay provides a specific and sensitive alternative to HPLC; it is rapid and inexpensive and with minor modifications may be applicable to most presently available Ca2+ channel antagonists.

Plasma homovanillic acid and tardive dyskinesia during neuroleptic maintenance and withdrawal

Plasma levels of homovanillic acid (HVA), a dopamine metabolite, were examined in 19 psychiatric inpatients during maintenance treatment on neuroleptic medications. A significant positive correlation was found between the level of HVA and the severity of tardive dyskinesia (TD) in these patients. Seven patients had their medication discontinued for 12 days. In spite of a fall in neuroleptic levels to negligible values, plasma HVA levels remained essentially stable while scores on the Abnormal Involuntary Movement Scale (AIMS) fell only slightly. The data support the hypothesis that some forms of TD may involve a persistent increase in presynaptic dopaminergic activity.

The effects of dose and duration of chronic pimozide administration on dopamine receptor supersensitivity

The neuroleptic drug pimozide was administered chronically to rats at different doses (0.75, 1.5 or 3.0 mg/kg, twice daily for 10 days) or for different durations (1.5 mg/kg twice daily for 5, 10, 20 or 40 days). At various intervals (4-40 days) after withdrawal dopamine (DA) receptor density in the striatum was assessed directly using specific [3H]-spiroperidol binding and indirectly by means of apomorphine-induced stereotypy and amphetamine-induced locomotor activity. The increase in the density of DA receptors was shown to be dependent upon the dose but not upon the duration of chronic pimozide. In contrast, the enhanced apomorphine-induced stereotypy was influenced by the duration but not by the dose of chronic pimozide. The potentiation of d-amphetamine-induced locomotor activity was found to vary as a function of both dose and duration of chronic pimozide administration. The results indicate that the augmentation of these apomorphine- and amphetamine-induced behaviors cannot be attributed solely to striatal DA receptor supersensitivity and that other, presently unspecified factors must contribute. It is also argued that in the absence of pharmacologically-induced DA receptor stimulation, the functional consequences of neuroleptic-induced increases in the density of striatal DA receptors are not apparent and remain unknown. In addition, these findings support the view that neuroleptic-induced proliferation of DA receptors cannot be the sole mechanism underlying tardive dyskinesia in man.

Lateral ventricular size and drug-induced Parkinsonism

Computed Tomography (CT) was used to assess lateral ventricular size in 20 psychiatric inpatients who had participated in at least 5 weeks of a fixed dose chlorpromazine (CPZ) trial. During treatment with CPZ, eight patients had required antiparkinsonian medication for treatment of rigidity. The ventricular brain ratio (VBR) of these eight patients was greater than that of either the 12 patients who did not require antiparkinsonian medication or a similarly aged control group of neurological patients, scanned for tension or migraine headaches. On the basis of these findings it is suggested that large lateral ventricular size may be associated with increased vulnerability to develop drug-induced parkinsonism.

[3H]spiroperidol binding on lymphocytes: changes in two different groups of schizophrenic patients and effect of neuroleptic treatment

[3H]spiroperidol binding to lymphocytes was measured in untreated paranoid or disorganized and treated paranoid schizophrenic patients. An increase in the Bmax was detected in untreated paranoid patients but a decrease was found in the disorganized patients. No difference was detected in the KD value. Neuroleptic treatment produced a decrease in the Bmax without affecting the KD value. Such results did not comply with the down regulation but might be explained by a change in membrane viscosity as [3H]spiroperidol binding sites on lymphocytes were coupled to phospholipid methylation.

Serum neuroleptic activity, prolactin, and tardive dyskinesia in schizophrenic outpatients

The authors measured serum neuroleptic activity and serum prolactin levels in 26 schizophrenic outpatients on prolonged neuroleptic therapy. Of the 24 patients, 11 had moderate to severe tardive dyskinesia, as assessed by the Abnormal Involuntary Movement Scale (AIMS). AIMS scores were positively correlated with age, duration of illness, and negative schizophrenic symptoms, but not with variables of neuroleptic exposure, current serum levels of neuroleptic activity, or serum prolactin levels. Neuroleptic activity and prolactin levels were positively correlated, and both variables also correlated with the current daily dose of neuroleptics.

Sedative effects and prolactin response to single oral doses of melperone

The pharmacokinetics of melperone and the relationship between plasma concentration and the effect on arousal and prolactin secretion after single oral doses (10, 25, 50 and 100 mg) was studied in normal subjects. Dose-dependent kinetics were indicated by the fact that higher plasma concentrations than expected were demonstrated after the 100-mg dose. Melperone decreased arousal and increased prolactin secretion in a dose-dependent manner. The level of arousal was correlated to melperone plasma concentration over the entire dose range. Prolactin secretion was also correlated to melperone plasma concentration, provided the relationship was studied separately for the individual melperone doses. Thus at higher doses, higher plasma concentrations are needed to elicit the same prolactin outflow. The possibility that reduced arousal reactions might contribute in the antipsychotic action of neuroleptic drugs was discussed.

Plasma levels of thiothixene by radioreceptor assay: clinical usefulness

Thirty-four newly admitted schizophrenic patients were treated with a fixed dose of thiothixene (0.44 mg/kg) for 4 weeks. Thiothixene and its active metabolites were measured by a new radioreceptor assay. Improvement occurred over the entire range of recorded plasma levels, but the chances of substantial improvement appear greater above 40 neuroleptic units (n.u.). The data do not support the notion of a "therapeutic window", in that higher plasma levels were not associated with side effects or clinical deterioration (although at extreme plasma levels this must of course be so). In 11 nonresponders dosage could not be increased because of side effects. If a non-responder with troublesome side effects has a low plasma level (less than 40 n.u.), it would seem prudent to switch to another antipsychotic drug.

Dopamine, serotonin and alpha-adrenergic receptor blocking activities in serum and their relationships to prolactin level in schizophrenic patients receiving long-term chlorpromazine treatment

The clinical application of a dopamine radioreceptor assay for neuroleptics has been proposed. Simultaneous monitoring of serum antidopaminergic (anti-DA), antiserotonergic (anti-5HT) antiadrenergic (anti-NA) activities may provide a better understanding of clinical effects of neuroleptics. Serum anti-DA and anti-5HT activities were estimated by competition for 3H-spiperone binding to dopamine and serotonin receptors in rat brain, respectively, and anti-NA activity by competition for 3H-WB-4101 binding to alpha-receptors. Thirty-one patients receiving maintenance doses of chlorpromazine (CPZ) chronically were studied. Serum activities varied among patients receiving the same dose, but correlated significantly with dose. Anti-DA activity also correlated with both anti-5HT anti-NA activities, and the average ratio of anti-5HT or anti-NA to anti-DA activity was slightly reduced by metabolism of CPZ. However, some patients had a different spectrum of serum activities from that of in vitro activities. Serum prolactin (PRL) correlated weakly with all the serum activities. The serum PRL anti-DA activity ratio appeared to be independent of anti-5HT or anti-NA activity, suggesting the predominant involvement of anti-DA activity in the stimulation of PRL release.