Disposition of haloperidol pyridinium and reduced haloperidol pyridinium in schizophrenic patients: no relationship with clinical variables during short-term treatment.

In an open clinical trial, serum concentrations of haloperidol pyridinium (C(HP+)) and reduced haloperidol pyridinium (C(RHP+)), as well as haloperidol (CH) and reduced haloperidol (C(RH)), were measured in 57 schizophrenic and schizoaffective inpatients during 6 weeks of short-term treatment. Psychopathology was monitored with the Brief Psychiatric Rating Scale (BPRS), and extrapyramidal adverse effects were assessed with the Extrapyramidal Symptom Rating Scale (EPS). Significantly linear relationships were found between haloperidol dose (D) and pyridinium metabolite serum concentrations, as well as between C(H) and the pyridinium metabolite serum concentrations. C(HP+) (range, 0.2-4.9 ng/mL) and C(RHP+) (range, 0.03-6.23 ng/mL) were low compared with C(H) and C(RH), being as mean values approximately 7% and 14% of C(H) and C(RH), respectively. Additionally, the values of C(RHP+) and the slope of the correlation of C(H) with the C(RHP+)/C(HP+) ratio were considerably lower than in a previous report of long-term treatment with haloperidol. This is explained by the shorter time of treatment of the present study. Carbamazepine comedication was found to not influence relative pyridinium metabolite serum concentrations C(HP+)/D and C(RHP+)/D. However, the aromatization ratios of haloperidol (C(HP+)/C(H)) and reduced haloperidol (C(RHP+)/C(RH)) were increased by concomitant carbamazepine. As the main result, no relationships between the pyridinium metabolite serum concentrations and clinical variables (BPRS change, EPS, dose of biperiden) were detected. For instance, the aromatization ratios C(HP+)/C(H) and C(RHP+)/C(RH) did not predict clinical improvement or extrapyramidal adverse effects. Therefore, no confirmation of the "pyridinium hypothesis," which suggests haloperidol pyridinium metabolites to be the origin of adverse effects and decreased therapeutic effect, can be derived from this study. However, the authors emphasize that pyridinium metabolites cannot be excluded as the origin of decreased therapeutic effect in long-term treatment and of adverse effects not investigated in the present study, such as tardive dyskinesia. Finally, it is concluded that the serum concentration of the parent drug remains the main variable of interest in the therapeutic drug monitoring of haloperidol during short-term treatment.

Reduced haloperidol does not interfere with the antipsychotic activity of haloperidol in the treatment of acute schizophrenia.

The aim of this study was to investigate the effect of reduced haloperidol, the main metabolite of the antipsychotic drug haloperidol, on psychopathology improvement and extrapyramidal adverse effects in acute schizophrenia. The steady-state pharmacokinetics of reduced haloperidol was studied. Serum concentrations of reduced haloperidol (C(RH)) and haloperidol (C(H)) were measured in an open clinical trial over 6 weeks of treatment in 57 acutely schizophrenic patients. Psychopathology was measured by the Brief Psychiatric Rating Scale and several subscales. The assay of extrapyramidal adverse effects was conducted by means of the Extrapyramidal Symptom Rating Scale. A significant serum concentration-therapeutic effect relationship (SCTER) of haloperidol of the same data has been demonstrated. In our study, the influence of the metabolite reduced haloperidol on the antipsychotic activity of haloperidol was analysed by means of regression analysis of the residuals of the SCTER of haloperidol with C(RH). In addition, the steady-state pharmacokinetics of reduced haloperidol and direct relationships between C(RH) and the metabolite ratio C(RH)/C(H) with psychopathology improvement and extrapyramidal adverse effects were investigated. Reduced haloperidol was not found to interfere with the antipsychotic action of the parent drug. Patients with elevated C(RH) or elevated metabolite ratio C(RH)/C(H) did not show consistently lower clinical improvements compared with the fitting curve of the SCTER of haloperidol and therefore no significant relationship between C(RH) and the residuals of the SCTER of haloperidol was detected. Furthermore, no significant result was found in the analysis of the direct relationships of C(RH) and C(RH)/C(H) with clinical variables which, for example, indicate decreased outcome with increased C(RH). In contrast, because of the pharmacokinetic dependence of C(RH) and C(H), a trend for a bisigmoidal relationship with C(RH) emerged for some outcome variables which was traced as an epiphenomenon from the bisigmoidal SCTER of the parent drug (e.g. change of hostility after 3 weeks). No relationship of reduced haloperidol with extrapyramidal adverse effects could be detected. It is concluded that serum concentrations of reduced haloperidol are of minor value for the interpretation of data of therapeutic drug monitoring of haloperidol in patients with acute schizophrenia. Reduced haloperidol does not act as a 'false neuroleptic'.

Therapeutic window of serum haloperidol concentration in acute schizophrenia and schizoaffective disorder.

Although several studies have been performed on the serum level-therapeutic effect relationship of neuroleptic drugs, the application of therapeutic drug-monitoring of neuroleptics is still a matter of controversy. Until now, haloperidol provided the most promising results. For this reason, an investigation of the dependence of clinical improvement on haloperidol serum levels was conducted in an acute psychiatric ward (Landeskrankenhaus Bernburg). In an open clinical trial haloperidol serum levels were measured in 57 acute schizophrenic patients for at least three weeks and correlated with clinical outcome (percent change of Brief Psychiatric Rating Scale, BPRS). A bisigmoidal model was used for data analysis. After three weeks of treatment, the major result proved to be a significant relationship between haloperidol serum level and therapeutic effect with pseudo-r2=0.316 and p=0.0031. Clinical improvement is enhanced by increasing haloperidol concentration up to about 10 ng/ml. It attains a maximum at about 10 ng/ml and decreases at haloperidol serum levels in a range of 10 ng/ml to 50 ng/ml. A simulation of this dependence of clinical improvement on serum levels, mediated by the variable dose design, can be excluded because of the results of a retrospective analysis of dosing behavior. Further evidence is thus provided for the dependence of therapeutic effect on the serum haloperidol concentration in acute schizophrenia. For practical application the position of a therapeutic window can be defined by a lower threshold level of about 5 ng/ml and an upper threshold of about 17 ng/ml. However, a maximal therapeutic effect is assured at 10 ng/ml. This should be the target value in serum level-guided dose adjustments.

Megabore capillary gas-liquid chromatographic method with nitrogen-phosphorus selective detection for the assay of haloperidol and reduced haloperidol in serum: results of therapeutic drug-monitoring during acute therapy of eight schizophrenics.

A gas chromatographic method using a HP-5 megabore capillary and nitrogen-phosphorus selective detection for the quantitative analysis of haloperidol (H) and reduced haloperidol (RH) in human serum or plasma is described. A 3-step liquid-liquid extraction is applied. The extraction yield of this procedure is 63% for haloperidol at 20 ng/ml. The limits of detection are 0.4 ng/ml for haloperidol and 1.0 ng/ml for the metabolite if 2 ml of body fluid are applied. At 10 ng/ml the within-day precision is 4.5% for H and 8.3% for RH. Serum levels of eight schizophrenic patients have been monitored weekly over a therapeutic period of six weeks. Seven patients mainly had metabolite ratios RH/H < 1 over the entire period of investigation. They exhibited a linear correlation between dose and serum concentration of haloperidol. In contrast, one patient had metabolite ratios RH/H > 1 over the entire period of the study. Due to considerable increased serum concentrations this patient did not show a linear correlation between the dose and the serum level of haloperidol.

Measurement of fluorescence changes of NAD(P)H and of fluorescent flavoproteins in saponin-skinned human skeletal muscle fibers.

Saponin-skinned human muscle fibers from M. vastus lateralis were immobilized in a quartz capillary to detect the fluorescence changes of NAD(P)H and of fluorescent flavoproteins. To get sufficient intense fluorescence signals from a small amount of muscle tissue the NAD(P)H fluorescence was excited by means of an HeCd laser at 325 nm and the flavoprotein fluorescence by an argon-ion laser at 454 nm or by the second wavelength of a HeCd laser at 442 nm. Using this experimental setup the fluorescence spectra of NAD(P)H, of alpha-lipoamide dehydrogenase and of electron-transfer flavoprotein were detected in saponin-skinned human muscle fibers. These fibers behaved identically to isolated mitochondria: (i) The addition of substrates caused an increase in reduction of mitochondrial NAD+, (ii) the addition of ADP caused its reoxidation, and (iii) the addition of respiratory chain inhibitors led to an almost complete reduction of NAD+. It was observed that the redox state of the NAD(P) system and of the alpha-lipoamide dehydrogenase reached after addition of 1 mM ADP correlates with the rate of active state respiration with NAD-dependent substrates. Therefore, this fluorimetric method is suitable to compare the mitochondrial oxidation capacities of NAD-dependent substrates in less then 5 mg wet weight muscle tissue. Moreover, the maximal changes in fluorescence of NAD(P)H and flavoproteins correlate with the amount of mitochondrial marker enzymes per milligram muscle tissue. Using this method a myopathy caused by a diminished content of mitochondria per milligram muscle tissue was observed.

Functional characterization of mitochondrial oxidative phosphorylation in saponin-skinned human muscle fibers.

The conditions of treatment of human skeletal muscle fibers from M. vastus lateralis with saponin were optimized to achieve complete permeabilization of cell membrane at intact mitochondrial oxidative phosphorylation. After 30 min of incubation with saponin all lactate dehydrogenase, 50% of creatine kinase, 30% of adenylate kinase and less than 20% of citrate synthase was released into the permeabilization medium. These skinned fibers behave similar to isolated mitochondria from human skeletal muscle: (i) the respiration with mitochondrial substrates can be stimulated by ADP, (ii) inhibited by carboxyatractyloside and (iii) it is possible to detect fluorescence changes of mitochondrial NAD(P)H on additions of substrates, uncoupler and cyanide. From a comparison of rates of respiration per cytochrome aa3 content of isolated human skeletal muscle mitochondria and saponin-skinned muscle fibers it was possible to calculate that almost 85% of mitochondria in those fibers are accessible for the investigation of oxidative phosphorylation. As shown by the investigation of biopsy samples of two patients with undefined myopathies these fibers are a suitable object for the replacement of isolated mitochondria in the diagnosis of mitochondrial myopathies and encephalomyopathies.