Liquid chromatographic determination of reduced haloperidol and haloperidol concentrations in packed red blood cells from humans

Haloperidol (H) is a neuroleptic drug that has one known biologically active metabolite, reduced haloperidol (RH). A liquid chromatographic method is described for the determination of both compounds in human red blood cell (RBC) samples. The drugs were extracted into hexane at high pH and back-extracted into 0.1M HCl. The acid solution was then analyzed by reversed-phase chromatography under the following conditions: column was ultrasphere ODS; eluant was acetonitrile:0.085M phosphate buffer (30:70), final pH was 3.5, flow rate was 2 mL/min; detection was by light absorption at 246 nm for H and 220 nm for RH. The minimum limits of quantitation for H and RH were 0.25 and 0.1 ng/mL of packed RBC respectively. For six selected patients on 10 or 20 mg per day of oral haloperidol the RBC to plasma concentration ratios for RH and H were 2.20 +/- 0.9 (SD) and 0.81 +/- 0.26, respectively. The data indicate that RH is more concentrated in RBC than in plasma.     

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.     

Simultaneous quantitation of buspirone and its major metabolite 1-(2-pyrimidinyl)piperazine in human plasma by high-performance liquid chromatography with coulometric detection

Buspirone is a member of the azapirone group of anxiolytic drugs and has one major metabolite, 1-(2-pyrimidinyl)piperazine (1-PP). The analyte, its metabolite and the internal standard were extracted from plasma utilizing solid-phase extraction columns. Chromatography was performed using isocratic reversed-phase high-performance liquid chromatography with coulometric end-point detection. The calibration graph was linear over the range 0–50 ng ml⁻¹ of plasma. The lower limits of quantitation for buspirone and 1-PP were 0.5 and 2 ng ml⁻¹, respectively, when 1 ml of plasma was extracted. The intra-assay relative standard deviations (RSD) over the range of the calibration graph varied from 4 to 12.5% for buspirone and 1-PP. The inter-assay RSD was 6.9% for 1-PP and 9.6% for buspirone. The recovery averaged 96% for buspirone and 66% for 1-PP. Plasma profiles of buspirone and 1-PP following oral dosing are presented.     

An ultrasensitive method for the measurement of fluphenazine in plasma by high-performance liquid chromatography with coulometric detection

A new sensitive analytical method is described for the quantitation of fluphenazine in 1 ml plasma samples after low oral doses of this antipsychotic agent. The drug is isolated by a simple one step extraction technique and analyzed by high-performance liquid chromatography (HPLC) with coulometric detection. The limit of detection for fluphenazine was 10 pg/ml of plasma and standard curves from 25 to 1,000 pg/ml were linear with an overall coefficient of variation (CV) of less than 5%. The lowest quantifiable concentration of 25 pg/ml could be determined with a CV of 4.7%. The sensitivity of the HPLC assay was such that plasma concentrations of fluphenazine could be followed for 2 days following administration of a single 10 mg oral dose of fluphenazine dihydrochloride to healthy volunteers. Known metabolites of fluphenazine did not interfere in the assay as they eluted with retention times different from that of fluphenazine.     

Intersubject variation in the pharmacokinetics of haloperidol and reduced haloperidol

Single oral doses (5 mg) of haloperidol were administered to 36 healthy men (26 black, 10 white) of whom 28 (22 black, 6 white) completed the study. Plasma samples harvested over 96 hours were analyzed for haloperidol and reduced haloperidol by means of a new high performance liquid chromatographic method. Reduced haloperidol was detectable in the plasma of only six of the 28 subjects (five blacks, one white). In these individuals reduced haloperidol plasma concentrations were generally much lower than those of the parent drug. This finding in the present single-dose study is in contrast to literature reports that have described levels of reduced haloperidol higher than those of the parent drug in some patients chronically mediated with haloperidol. There was wide intersubject variation in area under the plasma concentration versus time curve and apparent oral clearance values for haloperidol. The distributions of these pharmacokinetic parameters about their respective means were each leptokurtotic and skewed toward higher values. In each case the geometric mean gave a better estimate of central tendency than the arithmetic mean. Wide intersubject variation prevented the detection of significant differences in these pharmacokinetic parameters between black and white subjects or between smokers and nonsmokers.     

An improved sensitive assay for simultaneous determination of plasma haloperidol and reduced haloperidol levels by liquid chromatography using a coulometric detector

A simple, highly sensitive and specific high-performance liquid chromatographic method that uses a coulometric detector for the simultaneous assay of haloperidol and reduced haloperidol in human plasma has been developed, using bromoperidol as the internal standard. A reversed phase C8 5-microns column (25 x 0.46 cm) and a mobile phase of phosphate buffer (pH 7.0), acetonitrile, and methanol (40:20:40 vol/vol) are used for separating the analytes. The analytes are extracted from alkalinized plasma using a mixture of pentane and isopropanol (95:5 vol/vol) and purified by back extraction into a perchloric acid solution. Teflon tubes with screw caps are used throughout the extraction work. The compounds are oxidized at a potential of +0.90 V against a Ag/AgCl reference electrode. The detection limit of the assay is 50 ng/L using 1 mL of plasma. The average interassay coefficient of variation for samples of concentration 1-40 micrograms/L is approximately 8%. Possible drug interferences in the assay have been studied. The absolute recovery of the method is approximately 80%. The assay has been validated by quantitating 150 schizophrenic patients' samples.     

The plasma haloperidol and reduced haloperidol concentrations in chinese schizophrenic patients: Relationship between reduced haloperidol/haloperidol ratio and red blood cell haloperidol reductase activity

Fifteen chinese schizophrenic patients were given titrated doses of haloperidol (0.05-0.42 mg/kg) for two weeks. All these 15 patients were in clinical remission on maintenance dose of haloperidol. The mean plasma haloperidol and reduced haloperidol concentrations were 16.8 ± 4.8 ng/ml and 13.6- 5.7 ng/ml respectively. The plasma RHAL/HAL ratio was in the range of 0.13±1.94. These values were similar to that reported for the Japanese population. The frequency distribution appeared to be bimodal. RBC reductase activity were found to be distributed normally and no correlation was found between plasma RHAL/HAL ratio and RBC reductase activity.     

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 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     

Plasma haloperidol and clinical response: a role for reduced haloperidol in antipsychotic activity?

Seventeen hospitalized psychotic patients were treated with a fixed oral dose of haloperidol, 5 mg twice daily for 28 days. Most were chronic schizophrenics with an acute exacerbation of their illness. All patients also received benztropine 3 mg twice daily during the last 11 days of the study, regardless of the presence or absence of extrapyramidal side effects. No significant linear or curvilinear relationship was found between steady state plasma levels of haloperidol and clinical response measured by total Brief Psychiatric Rating Scale score. At 28 days, the correlations between plasma levels and percent improvement were rs = 0.187 (not significant) for haloperidol and rs = 0.582 (p = 0.04) for the hydroxymetabolite, reduced haloperidol. The correlation for the sum was rs = 0.511 (p = 0.078). Metabolite levels were substantially higher than plasma haloperidol, on the average 2.7 times greater. Eleven days of benztropine treatment had no significant effect on haloperidol or metabolite plasma levels or on clinical status. At the end of the study, nine of 17 patients (53%) had recovered as judged by discharge readiness. Within the limitations implied by the small number of patients, these data suggest that reduced haloperidol is an important component of plasma antipsychotic activity and cannot be neglected in correlative studies, and that a substantial proportion of patients--about half--can be successfully treated with only 10 mg of haloperidol. The routine use of large doses is thus not necessary for many patients.     

'High throughput' solid-phase extraction technology and turbo ionspray LC-MS-MS applied to the determination of haloperidol in human plasma

A quantitative method for the analysis of haloperidol in human plasma is described. Sample clean-up was performed by means of solid-phase extraction using 3M Empore™ extraction disk plates in the 96-well format, automated with a Canberra Packard pipetting robot. Separation was performed by reversed phase high performance liquid chromatography with turbo ionspray tandem mass spectrometric detection by monitoring the decay of protonated haloperidol of m/z 376 to its fragment at m/z 165, versus the decay of protonated haloperidol-D4 at m/z 380 to its fragment at m/z 169. The validated concentration range was from 0.100 to 50.0 ng ml⁻¹, with an inaccuracy and overall imprecision below 10% at all concentration levels. Validation results on linearity, specificity, precision, accuracy and stability are shown and are found to be adequate. The average sample preparation time for a batch of 96 samples is approximately 50 min. The chromatographic run time is 3 min. A sample throughput of at least 240 samples per day can be achieved.     

Quantitative determination of haloperidol in human plasma by high-performance liquid chromatography

We present a method for the quantitative determination of haloperidol in human plasma. The high-performance liquid chromatographic method of analysis is a significant advancement in terms of ease and speed of haloperidol determination. The drug and the internal standard, chlorohaloperidol, are extracted from 2.0 ml of serum or plasma, back-extracted into the aqueous mobile phase, separated on a C-18 reversed-phase column, and monitored at 254 nm. The potential interference by other drugs was evaluated and was found to be negative. The method is sensitive to at least 5 ng/ml of extracted material and is suitable for drug measurement in the therapeutic range (5-20 ng/ml) and in the toxic range (greater than 50 ng/ml).     

Alterations in dopamine metabolism after chronic administration of haloperidol. Possible role of increased autoreceptor sensitivity

Basal levels of the metabolites of dopamine (DA) were reduced following the chronic administration of haloperidol. The ability of small doses (50 or 100 micrograms/kg) of apomorphine to reduce the concentrations of the metabolite of DA, homovanillic acid (HVA), was also enhanced following the chronic administration of haloperidol. In addition, the accumulation of DA and of the metabolite of DA, 3-methoxytyramine (3-MT), in rats treated with pargyline was reduced following the chronic administration of haloperidol, suggesting that basal turnover and release of DA also may be reduced. These findings are discussed in relation to possible changes in the sensitivity of DA autoreceptors and the activity of DA-containing neurons.     

Simultaneous extraction and quantitation of fentanyl and norfentanyl from primate plasma with LC/MS detection

The quantitation of both fentanyl and its desalkyl metabolite, norfentanyl, in plasma using LC/MS has not been previously described. The detection and quantitation of fentanyl and norfentanyl was achieved using LC/MS detection. The liquid-liquid extraction used toluene as the organic phase. Chromatography was carried out using a Zirchrom-PBD (50 mm x 2.1 mm, 3 microm) column with a mobile phase of acetonitrile-ammonium acetate (10 mM), citrate (0.1 mM, pH 4.4) (45:55, v/v) with a flow rate of 0.3 ml/min. Mass spectroscopy detection was performed using ESI in the positive mode. The LOQ for fentanyl was 25 pg/ml and norfentanyl was 50 pg/ml. For the concentrations of 75, 250, and 750 pg/ml, respectively, fentanyl had inter-day precisions of 6.6, 7.2, and 6.6% with accuracies of 4.0, 5.1, and 5.1% and intra-day precisions of 1.6, 1.9, and 1.9% with accuracies of 11.6, 9.4, and 8.4%, and norfentanyl had inter-day precisions of 7.4, 0.3, and 0.7% with accuracies of 9.1, 8.8, and 12.3% and intra-day precisions of 5.3, 1.4, and 0.1% with accuracies of 10.9, 8.9, and 12.8%. The recoveries of fentanyl were 85, 92, and 75% and of norfentanyl were 40, 49, and 46% at the 75, 250, and 750 pg/ml concentrations, respectively.     

Reduced haloperidol plasma concentration and clinical response in acute exacerbations of schizophrenia

Twenty-nine hospitalized patients suffering acute exacerbations of schizophrenia were treated for 2 weeks with fixed daily oral doses of haloperidol prospectively calculated to achieve a haloperidol plasma concentration of either 8–18 ng/ml or 25–35 ng/ml. Reduced haloperidol as well as haloperidol concentrations were assayed to determine if the former enhanced the predictability of response. Week 2 haloperidol plasma concentrations were negatively correlated to clinical response as measured by the percentage change in the BPRS score from baseline (r=–0.43,P<0.05). In contrast, week 2 plasma concentrations of reduced haloperidol, total haloperidol (haloperidol+reduced haloperidol), and reduced haloperidol/haloperidol ratio did not correlate with the change in the BPRS score. Chi-square analysis concluded that patients with ratios greater than one were no less likely to be treatment responders (<25% improvement in BPRS from baseline and week 2 BPRS <55) than those with ratios less than one. Although these data lend additional support to reports of a curvilinear relationship between haloperidol plasma concentration and clinical response, they also suggest that reduced haloperidol plasma concentrations are of no value in predicting treatment response.From the Mental Health Research Center — Major Psychoses, funded in part by NIMH Grant #5 P50 MH43271     

Biliary excretion of reduced haloperidol glucuronide

The biliary excretion of haloperidol and reduced haloperidol were investigated in the guinea pig. Bile duct cannulated guinea pigs were administered a single intraperitoneal dose of haloperidol (1 mg/kg). Bile was continually collected over a 12-h period. Aliquots of the bile samples were analyzed by HPLC for free haloperidol and reduced haloperidol. The remaining portions of the bile samples were incubated with beta glucuronidase and reanalyzed for haloperidol and reduced haloperidol. Although no significant amount of haloperidol glucuronide was detected in the bile, a new metabolite of reduced haloperidol, reduced haloperidol glucuronide, was found. The amount of reduced haloperidol excreted in the bile as the glucuronide conjugate was significantly higher than the amount of haloperidol or reduced haloperidol. These results imply that reduced haloperidol glucuronide may play a role in the disposition of haloperidol and/or its metabolite, reduced haloperidol.     

Reversible metabolism of haloperidol and reduced haloperidol in Chinese schizophrenic patients

Haloperidol disposition has been associated with reversible metabolism: it is reversibly reduced to its metabolite, reduced haloperidol, which has less pharmacologic activity than the parent compound. To characterize the interconversion process, six healthy male schizophrenics were administered a single dose of 10 mg haloperidol or reduced haloperidol in a randomized crossover manner. Using a general pharmacokinetic model for the interconversion process, the clearances of haloperidol and reduced haloperidol are 1.15±0.32 l/h/kg and 0.76±54 l/h/kg, respectively. These clearances are similar to that obtained by the usual mammillary model analysis. With a single 10 mg dose administration of either drug, about 23% of the biotransformation of haloperidol involves the reduction pathway. Back conversion from the reduced metabolite to the parent drug through oxidation contributes even less to the total biotransformation of reduced haloperidol. This action of interconversion or saturation under chronic drug administration is unknown. Reversible metabolism of haloperidol could partially account for the wide therapeutic range for haloperidol as reported in the literature.Presented at the 10th Annual Meeting of the American College of Clinical Pharmacy August 6–9, 1989     

Sensitive electrochemical high-performance liquid chromatography assay for the simultaneous determination of haloperidol and reduced haloperidol

An electrochemical HPLC method for the simultaneous determination of haloperidol and reduced haloperidol in plasma is presented. Chlorohaloperidol serves as the internal standard. A cyanopropyl bond elut column was used for sample preparation. The eluate was evaporated and reconstituted with mobile phase and injected onto a nitrile bonded column. The chromatographic system consisted of an ESA Coulochem detector operated in the screen mode. Intra- and interassay coefficients of variation for both compounds were less than 7%, with a sensitivity limit of 20 pg on the column. A plasma level-time profile is presented to illustrate the sensitivity and applicability of this assay in small animal and human pharmacokinetic studies.     

Haloperidol and reduced haloperidol concentrations in plasma and red blood cells from chronic schizophrenic patients

In a double-blind, placebo-controlled study, 15 drug-free chronic schizophrenic inpatients were treated with a fixed dose of haloperidol for 6 weeks. Haloperidol and its metabolite, reduced haloperidol, were measured in plasma and red blood cells after 2, 4, and 6 weeks of treatment. Behavioral change was rated using the Brief Psychiatric Rating Scale (BPRS). Not only the raw concentrations, but also blood compartment sums and ratios of these four drug measurements were tested for their strength of association with behavioral improvement. Positive associations with some BPRS subscales at some time points emerged; however, no significant correlations were found to extend across all time points measured. There was a trend in this cohort for negative symptom improvement to be associated with the ratio of haloperidol to reduced haloperidol in red blood cells. The ratio of haloperidol to reduced haloperidol in plasma was always greater than that in the red blood cells for all patients, reflecting an accumulation of the metabolite in red blood cells.     

Lack of significant pharmacokinetic interaction between haloperidol and grapefruit juice

The effects of repeated ingestion of grapefruit juice, an inhibitor of cytochrome P4503A4 (CYP3A4), on the steady-state plasma concentrations of haloperidol and reduced haloperidol were examined. Twelve schizophrenic inpatients receiving haloperidol 12 mg/day, ingested grapefruit juice 600 ml/day for 7 days. Blood samples were collected before and during grapefruit juice coadministration and 1 week after its discontinuation together with an assessment of clinical status. Plasma drug concentrations were measured using high-performance liquid chromatography. Clinical status for each patient was assessed by the Brief Psychiatric Rating Scale (BPRS) and the UKU side-effect rating scale (UKU). Plasma concentrations of haloperidol and reduced haloperidol during grapefruit juice coadministration (9.0 +/- 3.0 and 2.6 +/- 1.4 ng/ml, respectively) were not significantly different from those before grapefruit juice coadministration (9.1 +/- 2.8 and 2.6 +/- 1.5 ng/ml) or those 1 week after its discontinuation (8.8 +/- 2.7 and 2.6 +/- 1.3 ng/ml). There was no change in the scores of BPRS or UKU during the study period. The present results shows that grapefruit juice does not affect the plasma concentrations of haloperidol and reduced haloperidol or clinical status in patients receiving haloperidol.