Effects of carbamazepine and valproate on haloperidol plasma levels and on psychopathologic outcome in schizophrenic patients.

The objective of this study was to compare the effects of carbamazepine (CBZ) and valproate (VPA) cotreatment on the plasma levels of haloperidol and on the psychopathologic outcome in schizophrenic disorders. In this controlled clinical trial, 27 patients with an ICD-10 diagnosis of schizophrenia (N = 24) or schizoaffective disorder (N = 3) were randomly assigned to receive 4 weeks of treatment with either haloperidol alone, haloperidol with CBZ, or haloperidol with VPA. Whereas the haloperidol dose remained stable, the antiepileptic drug doses were adjusted to achieve therapeutic plasma levels. Clinical state was rated by the Positive subscale of the Positive and Negative Syndrome Scale and the Inpatient Multidimensional Psychiatric Scale. The use of CBZ was associated with significantly lower haloperidol plasma levels and with a worse clinical outcome compared with antipsychotic monotherapy. VPA had no significant effect on either plasma levels or on psychopathology. Our results suggest that comedication with haloperidol and CBZ is associated with a high risk for treatment failure. This might be a result of a pharmacokinetic interaction on the hepatic level. The concomitant use of VPA with neuroleptic therapy is not impaired by clinically significant drug interactions, but it is not associated with a better outcome under our conditions.     

Effects of smoking on haloperidol and reduced haloperidol plasma concentrations and haloperidol clearance

Plasma concentrations of haloperidol and its reduced metabolite (reduced haloperidol) were investigated in cigarette smokers (N=23) and nonsmokers (N=27). Steady-state plasma concentrations were obtained 12 h post bedtime dose. Haloperidol and reduced haloperidol concentrations were determined by RIA. Reduced haloperidol was separated by selective succinylation and liquid chromatography. Patients were clinically assessed with the Clinical Global Impression Scale (CGIS). Smokers had significantly lower haloperidol and reduced haloperidol plasma concentrations than nonsmokers (P<0.01, P<0.05). Clearance of haloperidol was significantly greater in smokers compared to nonsmokers (P=0.0052). CGIS assessments did not show significant differences between smokers and non-smokers. Plasma concentrations should be carefully monitored when patients either start or stop smoking.Presented at the IV World Congress of Biological Psychiatry, Philadelphia, PA, September 8–13, 1985     

Disposition of haloperidol and reduced haloperidol plasma levels after single dose haloperidol decanoate administration

A single dose of haloperidol decanoate 100 mg was administered to 15 schizophrenic patients. Blood samples were obtained prior to injection, 1 h, 3 h, 6 h, 8 h, 1 day, 2 days, 3 days, 4 days, 5 days, 6 days, one week, two weeks, three weeks and four weeks post-injection. Haloperidol and its reduced metabolite, reduced haloperidol, plasma levels were assayed by HPLC with electrochemical detection. The pharmacokinetic parameters of haloperidol were determined. The mean time of maximal (T_max) plasma levels for haloperidol was 5·73 ± 0·80 days. The haloperidol plasma levels showed a biexponential decline with an elimination half-life of 15·78 ± 5·90 days. Reduced haloperidol was rapidly formed from the haloperidol. The T_max of reduced haloperidol was 7·00 ± 2·35 days. The mean ratio reduced haloperidol/haloperidol was 0·155 ± 0·111. Since the T_max occurs at approximately six days, a weekly loading dose of haloperidol decanoate is feasible during the transition from oral to depot therapy.     

Significant dose effect of carbamazepine on reduction of steady-state plasma concentration of haloperidol in schizophrenic patients

A reduction in haloperidol concentration induced by carbamazepine coadministration has been consistently reported. However, the degree of this reduction is very different among individuals treated with various doses of carbamazepine. Thus, we investigated dose effect of carbamazepine on the steady-state plasma concentration of haloperidol. Eleven excited schizophrenic inpatients, despite receiving haloperidol 12 mg/d, were treated with incremental doses of carbamazepine for 6 weeks (100, 300, 600 mg/d for 2 weeks each). Plasma drug concentrations were monitored together with clinical assessments before and after each phase of the 3 carbamazepine doses. Mean haloperidol concentrations during coadministration of carbamazepine 100, 300, and 600 mg/d were 75%, 39%, and 15%, respectively, of corresponding variables before carbamazepine coadministration. Negative linear correlations were observed between dose or plasma concentration of carbamazepine and the degree of reduction in haloperidol concentration. Mean carbamazepine dose and plasma carbamazepine concentrations at 50% reduction of haloperidol concentration were 240 mg/d and 3.5 microg/mL, respectively. Scores in total and excitement symptoms were significantly reduced after carbamazepine coadministration, whereas no changes were observed in other clinical symptoms or any of the subgroup side effects. Therefore, this study indicates that carbamazepine decreases plasma haloperidol concentration in a dose-dependent or concentration-dependent manner, and that reduction in haloperidol concentration is apparent even at subtherapeutic dose of carbamazepine.     

ABCB1基因多态性对卡马西平血药浓度的影响

目的:探讨ABCB1基因多态性对卡马西平血药浓度的影响。方法:采用荧光偏振免疫法(FPIA)测定275例口服卡马西平癫痫患者的血药浓度,聚合酶链式反应-限制性片段长度多态性方法(PCR-RFLP)或直接测序法检测ABCB1多态性位点C1236T、G2677T/A和C3435T的基因型。单因素方差分析计算各SNP位点不同基因型对应的卡马西平血药浓度是否有差异。结果:G2677T/A不同基因型对应的调整后血药浓度均值之间差别有显著性,TT基因型对应的调整后血药浓度显著高于GG型(P=0.001)。C1236T、C3435T各基因型对应的调整后血药浓度均值差别无统计学意义(P>0.05)。结论:ABCB1基因SNP位点G2677T/A的基因多态性对口服卡马西平癫痫患者的血药浓度有影响,提示TT基因型的患者可适当减少药物使用剂量。     

Plasma propranolol levels and their effect on plasma thioridazine and haloperidol concentrations

The relationship between chronic oral dosage with a long-acting formulation of propranolol and plasma propranolol levels 22 to 23 hours later is described in 12 adult male patients with organic brain disease. Separately, the effects on plasma levels of thioridazine plus metabolites with concomitant rising dose long-acting propranolol administration were studied in five patients. Significant dose-related increases in levels of thioridazine and metabolites were found when long-acting propranolol was given. No changes in haloperidol levels were found in three patients studied in a similar protocol.     

Haloperidol and reduced haloperidol plasma levels in selected schizophrenic patients

The first measurements of haloperidol (HL) and its reduced metabolite hydroxyhaloperidol (RH) in plasma versus clinical response in five chronic schizophrenic patients are reported. HL and RH were measured by a radioimmunoassay with a low coefficient of variation. Patients were selected based on poor response or the need for high dosage and were rated with the Clinical Global Impression Scale. Daily HL dosage range was 0.5 to 1.5 mg/kg. HL plasma concentrations ranged from 14 to 98 ng/ml. RH plasma concentrations ranged from 10 to 319 ng/ml. Four patients did not respond to HL therapy; two of these improved dramatically when switched to fluphenazine. The four nonresponding patients had higher RH than HL concentrations. RH seems to be present in plasma in significant concentrations, and further investigation of the relationships of RH and HL plasma levels versus response is needed.     

Effects on haemodynamics and plasma noradrenaline levels in man of long term treatment with imipramine,haloperidol and chlorpromazine

Summary Haemodynamic effects in patients treated with imipramine and haloperidol were studied at rest and during exercise and were related to the arterial plasma levels of noradrenaline. The results were compared with earlier observations on untreated and chlorpromazine-treated patients studied by the same techniques. After imipramine in a daily dose of 150–350 mg, there was a tendency for the heart rate to increase but no other particular haemodynamic effects were observed. During imipramine treatment noradrenaline levels were not increased compared to the controls, at a work load of less than 900 kpm/min, after which there appeared to be some increase. After haloperidol in a dose of 12–22 mg per day no changes were observed in the circulation or plasma noradrenaline levels. More marked effects on the circulation and plasma noradrenaline levels were found in patients treated with very large doses of chlorpromazine (1800–3600 mg daily). They showed a lower cardiac output, stroke volume and systolic and mean arterial blood pressure during exercise than the other groups. In the chlorpromazine-treated group the heart rate was higher both at rest and during mild exercise. The plasma noradrenaline levels were higher at rest and at all work loads than in the other patients. It may be concluded that the haemodynamic effects of chlorpromazine and its effects on the plasma noradrenaline levels are primarily due to its peripheral -adrenergic receptor blocking effect, which induces a compensatory increase in sympathetic nerve impulse flow. However, an increased overflow of noradrenaline from the nerve terminals per nerve impulse due to drug effects at the nerve terminal-effector cell level might also contribute to the high plasma levels of noradrenaline found after chlorpromazine treatment.     

Effects of long-term carbamazepine treatment on water metabolism and plasma vasopressin concentration

Summary Plasma osmolality, sodium and vasopressin were measured in 7 patients before and during long-term treatment with carbamezepine, under resting conditions, and following an oral water load of 20 ml/kg body weight. During carbamazepine treatment, the ability to excrete the oral water load was decreased, the urine/plasma osmolality ratio was higher, and the free water clearance was lower. In two patients, the ability to excrete the oral water load was severely impaired, and the free water clearance remained negative following water loading. Plasma osmolality and sodium concentration were significantly lower during carbamazepine administration, but despite this the plasma vasopressin concentration remained unchanged or was even slightly increased. Four patients showed inappropriately high vasopressin concentrations in relation to the corresponding plasma osmolality when taking carbamazepine. The findings suggest a decrease in plasma osmolality during carbamazepine treatment, which might account for the inappropriate secretion of vasopressin. The latter might cause clinical symptoms of water intoxication, as has previously been reported in a few patients on carbamazepine therapy.     

Predicting haloperidol occupancy of central dopamine D2 receptors from plasma levels

Positron emission tomography (PET) is increasingly being used to study dopamine receptor occupancy and the clinical effects of antipsychotic medication. Dopamine D₂ receptor occupancy has been shown to predict several clinical effects of antipsychotic medication including therapeutic response, motor and endocrine side-effects. Plasma levels may be used as a surrogate marker for central occupancy if the relationship between these two measures may be accurately described. This study was designed to test the capacity of a previously derived relationship equation (%D₂ occupancy=plasma level/ED₅₀+plasma level, where ED₅₀= 0.40 ng/ml) to predict striatal D₂ occupancy from plasma level. Twenty-one patients receiving treatment with low dose haloperidol underwent a ¹¹C-raclopride PET scan to measure D₂ occupancy. The D₂ occupancy levels were accurately predicted by use of the previously generated equation with only a small degree of error (3.89% CI 0.45–7.33). Predicted and measured D₂ occupancy values correlated closely (Pearson’s r=0.864, P=0.003). The study indicates that reliable prediction of D₂ occupancy from plasma levels is possible. This provides a potentially useful surrogate measure of D₂ occupancy for research and possibly clinical practice, as the routine use of PET to measure occupancy levels is not feasible. Received: 4 February 1999 / Final version: 22 October 1999     

Determination of haloperidol and reduced haloperidol in the plasma and blood of patients on depot haloperidol

We developed a sensitive HPLC assay to measure haloperidol (HA) and its metabolite, reduced haloperidol (RH), in plasma and whole blood. The conditions under which HA might be converted to RH during collection and analysis of blood were examined. Provided the blood was kept at 0° C, erythrocyte ketone reductase activity was insignificant. The solid phase extraction method did not generate RH. We studied ten patients taking 25–400 mg/month of HA decanoate and one patient for 4 weeks after the daily oral dose of 120 mg HA was ceased. In the patients on depot HA, the plasma and blood concentrations of HA were not significantly different (P>0.1). For the first time, RH was detected in plasma patients on depot drug, but only in three cases. In contrast, RH was present in the blood of eight of these patients. The accumulation of RH in red blood cells was also evident in the patient on oral HA, in whom the mean ratio of RH concentrations in whole blood to plasma was 3.6±1.1. Plasma concentrations of HA correlated highly with total neuroleptic activity measured by a radioreceptor assay. Compared to plasma, analysis of concentrations of HA and RH in blood has the advantages of greater sensitivity, of using smaller volumes of blood and of avoiding the efflux of HA and RH during separation of plasma and red cells.     

Effects of debrisoquin and haloperidol on plasma homovanillic acid concentration in schizophrenic patients

Plasma levels of the dopamine metabolite homovanillic acid (pHVA) may potentially reflect upon central dopamine activity. This study examines the effects of debrisoquin, haloperidol, and the two drugs combined on pHVA concentrations of schizophrenic patients. Debrisoquin is a drug that suppresses the peripheral formation of homovanillic acid without affecting the central formation. Acute haloperidol administration consistently increased pHVA concentrations in patients pretreated or not pretreated with debrisoquin, suggesting that this increment reflects haloperidol's central and not peripheral effects.     

In vivo effects of carbamazepine and haloperidol on GABA neurotransmission and LH secretion

The in vivo effects of carbamazepine (CBZ) and haloperidol (HAL) on the neuroendocrine pre-optico-pituitary feedback system were studied by local application of the drugs, in single and in combination mode, through a push-pull cannula into the pre-optic area and measurement of their local effects on γ-aminobutyric acid (GABA) and their distant effects on a subsequent biological response: the pituitary luteinizing hormone (LH) secretion. The perfusion flow rate was 20 μl cerebrospinal fluid (CSF)/min; the fraction period was 15 min. Perfusion with 8 μg CBZ/ml CSF caused a reduction in pre-optic pre-synaptic GABA release and, concomitantly, a suppression of plasma LH levels. Application of 100 ng HAL/ml CSF also caused a reduction in GABA release, but no significant change in plasma LH levels. During the combined perfusion, the effects of CBZ and HAL did not add up with regard to the pre-optic GABA release. These results suggest that both drugs interact with the GABA system, but they may involve two different mechanisms of action. Due to the known inhibitory role of pre-optic GABA in pituitary LH secretion, it can be inferred that, in contrast to HAL, CBZ increases post-synaptic GABAergic transmission.     

Lower plasma levels of haloperidol in smoking than in nonsmoking schizophrenic patients.

The impact of smoking on plasma haloperidol (HAL) concentrations was investigated in 66 Japanese male schizophrenic inpatients treated orally with HAL. The subjects consisted of 22 nonsmokers and 44 smokers each smoking ten cigarettes per day. Plasma concentrations of HAL were determined by an enzyme immunoassay method. There were significant positive correlations between the plasma HAL concentration and the daily dose of HAL per kg body weight (Y = 58.1X-0.01 (r = 0.86)). Smokers had significantly lower HAL concentrations per daily dose of HAL/kg body weight than nonsmokers (smokers vs. nonsmokers = 54.3+/-16.6 vs. 70.6+/-23.2 ng/mL/mg/kg). In doses less than 0.2 mg/kg of HAL, smokers showed significantly lower HAL concentrations per daily dose of HAL/kg body weight than nonsmokers (smokers vs. nonsmokers = 55.1+/-14.4 vs. 79.5+/-27.1 ng/mL/mg/kg), whereas no significant difference in HAL concentrations per daily dose of HAL/kg body weight was observed between smokers and nonsmokers when treated with more than 0.2 mg/kg (smokers vs. nonsmokers = 52.9+/-20.7 vs. 60.0+/-11.1 ng/mL/mg/kg). Our results indicate that smoking may induce the enzyme(s) metabolizing HAL, which results in lower plasma HAL concentrations in smokers than in nonsmokers, particularly at low doses of HAL.     

Effect of switching carbamazepine to oxcarbazepine on the plasma levels of neuroleptics. A case report

Carbamazepine was switched to its 10-keto analogue oxcarbazepine among six difficult-to-treat schizophrenic or organic psychotic patients using concomitantly haloperidol, chlorpromazine or clozapine. This change resulted within 2–4 weeks in the 50–200% increase in the plasma levels of these neuroleptics and the appearance of extrapyramidal symptoms. None of the patients showed any clinical deteriotation during the following 3–6 months. The results of this case report support the idea that in contrast with carbamazepine oxcarbazepine does not induce the hepatic microsomal enzyme systems regulating the inactivation of antipsychotic drugs.     

Effects of carbamazepine on hepatic glutathione level in rats and determination of carbamazepine and its epoxide metabolite in plasma by HPLC

We investigated whether carbamazepine, which is known to be metabolized to an electrophilic epoxide derivative in the body, causes any decrease, analogous to the action of epoxides, of hepatic glutathione (GSH) level in rats. Carbamazepine was administered to rats and liver GSH levels were determined spectrophotometrically. Neither a single low nor repeated low doses (30 mg/kg) of carbamazepine (CBZ) produced a statistically significant difference in GSH levels relative to controls. A single high dose of CBZ (100 mg/kg) produced a large and significant decrease relative to control (GSH level 3.82 +/- 0.64 vs 6.54 +/- 0.45 mumol GSH/g liver). CBZ and its metabolite carbamazepine-10,11-epoxide were determined in plasma by HPLC after the high dose of carbamazepine administration. The concentrations of carbamazepine and carbamazepine-10,11-epoxide were 18.9 +/- 2.9 micrograms/ml and 10.7 +/- 2.8 micrograms/ml, respectively.     

Effects of conjugated estrogens on plasma butaperazine levels

A randomly assigned control-experimental grouping with a crossover design, using subjects as their own controls, was utilized to study the effects of conjugated estrogens on plasma butaperazine (Repoise) levels in post-menopausal female subjects. Significantly higher plasma butaperazine levels were measured following both a single loading dose and with maintenance doses of oral butaperazine in subjects when they were taking conjugated estrogens as compared to when they were not taking conjugated estrogens. The underlying mechanisms for these findings and their clinical implications are discussed briefly.This research was supported in part by grant GM 15431 from the National Institutes of Health, grant MH 11468 from the National Institute of Mental Health, and by research support from the State of Tennessee Department of Mental Health.