A gas chromatographic method for determining haloperidol. A sensitive procedure for studying serum concentration and pharmacokinetics of haloperidol in patients.
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1. The authors attempted to correlate plasma concentrations in H/rH and clinical efficacy from 8 schizophrenic patients (DSM IIIR) on H. 2. No significant correlations were found between H, rH plasma levels and positive and negative subscale for each patient. 3. The authors observed an opposite evolution concerning the mean results between plasma concentrations and PANSS total score.
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OBJECTIVE: To determine the antipsychotic efficacy and extrapyramidal safety of intramuscular (i.m.) olanzapine and i.m. haloperidol during the first 24 hours of treatment of acute schizophrenia. METHOD: Patients (n = 311) with acute schizophrenia were randomly allocated (2:2:1) to receive i.m. olanzapine (10.0 mg, n = 131), i.m. haloperidol (7.5 mg, n = 126), or i.m. placebo (n = 54). RESULTS: After the first injection, i.m. olanzapine was comparable to i.m. haloperidol and superior to i.m. placebo for reducing mean change scores from baseline on the Brief Psychiatric Rating Scale (BRPS) Positive at 2 hours (-2.9 olanzapine, -2.7 haloperidol, and -1.5 placebo) and 24 hours (-2.8 olanzapine, -3.2 haloperidol, and -1.3 placebo); the BPRS Total at 2 hours (-14.2 olanzapine,-13.1 haloperidol, and -7.1 placebo) and 24 hours (-12.8 olanzapine, -12.9 haloperidol, and -6.2 placebo); and the Clinical Global Impressions (CGI) scale at 24 hours (-0.5 olanzapine, -0.5 haloperidol, and -0.1 placebo). Patients treated with i.m. olanzapine had significantly fewer incidences of treatment-emergent parkinsonism (4.3% olanzapine vs 13.3% haloperidol, P = 0.036), but not akathisia (1.1% olanzapine vs 6.5% haloperidol, P = 0.065), than did patients treated with i.m. haloperidol; they also required significantly less anticholinergic treatment (4.6% olanzapine vs 20.6% haloperidol, P < 0.001). Mean extrapyramidal symptoms (EPS) safety scores improved significantly from baseline during i.m. olanzapine treatment, compared with a general worsening during i.m. haloperidol treatment (Simpson-Angus Scale total score mean change: -0.61 olanzapine vs 0.70 haloperidol; P < 0.001; Barnes Akathisia Scale global score mean change: -0.27 olanzapine vs 0.01 haloperidol; P < 0.05). CONCLUSION: I.m. olanzapine was comparable to i.m. haloperidol for reducing the symptoms of acute schizophrenia during the first 24 hours of treatment, the efficacy of both being evident within 2 hours after the first injection. In general, more EPS were observed during treatment with i.m. haloperidol than with i.m. olanzapine.
Haloperidol and reduced haloperidol are interconverted. The plasma concentrations of these two butyrophenones have been suggested to be important factors in determining the clinical effect of haloperidol treatment. The steady-state plasma concentrations of haloperidol and reduced haloperidol were measured in 322 Taiwanese schizophrenic patients using high performance liquid chromatography. The daily doses of haloperidol varied from 5 to 200 mg (mean +/- SD, 35.3 +/- 34.6 mg). There was a positive correlation between plasma concentrations and doses, following the equation: haloperidol concentration (ng/mL) = 0.88 x dose (mg/day)-1.66. However, the interpatient variation in haloperidol concentrations was up to ten-fold even in patients receiving the same dose (20 mg/day, n = 88). The expected values were about 10% to 50% higher than those reported in Caucasian patients. The plasma reduced haloperidol concentrations were significantly lower than, and correlated with, those of haloperidol in patients with haloperidol levels lower than 25 ng/mL. However, once haloperidol exceeded 25 ng/mL, reduced haloperidol levels rapidly elevated and appeared significantly higher than haloperidol levels. While haloperidol could reach its steady state in about 1 week, reduced haloperidol needed at least 4 weeks to do so. Haloperidol doses of less than 30 mg/day and plasma concentrations lower than 25 ng/mL are recommended for most Chinese patients.
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.
Haloperidol is commonly used in the therapy of patients with acute and chronic schizophrenia. The enzymes involved in the biotransformation of haloperidol include cytochrome P450 (CYP), carbonyl reductase and uridine diphosphoglucose glucuronosyltransferase. The greatest proportion of the intrinsic hepatic clearance of haloperidol is by glucuronidation, followed by the reduction of haloperidol to reduced haloperidol and by CYP-mediated oxidation. In studies of CYP-mediated disposition in vitro, CYP3A4 appears to be the major isoform responsible for the metabolism of haloperidol in humans. The intrinsic clearances of the back-oxidation of reduced haloperidol to the parent compound, oxidative N-dealkylation and pyridinium formation are of the same order of magnitude, suggesting that the same enzyme system is responsible for the 3 reactions. Large variation in the catalytic activity was observed in the CYP-mediated reactions, whereas there appeared to be only small variations in the glucuronidation and carbonyl reduction pathways. Haloperidol is a substrate of CYP3A4 and an inhibitor, as well as a stimulator, of CYP2D6. Reduced haloperidol is also a substrate of CYP3A4 and inhibitor of CYP2D6. Pharmacokinetic interactions occur between haloperidol and various drugs given concomitantly, for example, carbamazepine, phenytoin, phenobarbital, fluoxetine, fluvoxamine, nefazodone, venlafaxine, buspirone, alprazolam, rifampicin (rifampin), quinidine and carteolol. Overall, drug interaction studies have suggested that CYP3A4 is involved in the biotransformation of haloperidol in humans. Interactions of haloperidol with most drugs lead to only small changes in plasma haloperidol concentrations, suggesting that the interactions have little clinical significance. On the other hand, the coadministration of carbamazepine, phenytoin, phenobarbital, rifampicin or quinidine affects the pharmacokinetics of haloperidol to an extent that alterations in clinical consequences would be expected. In vivo pharmacogenetic studies have indicated that the metabolism and disposition of haloperidol may be regulated by genetically determined polymorphic CYP2D6 activity. However, these findings appear to contradict those from studies in vitro with human liver microsomes and from studies of drug interactions in vivo. Interethnic and pharmacogenetic differences in haloperidol metabolism may explain these observations.
Developing and adult Sprague-Dawley rats were tested after acute or repeated haloperidol administration. Although 8-day-old rat pups showed a form of immobility in response to a single injection of haloperidol (1 mg/kg), 14-day-old rats did not show any behavioral response to the neuroleptic. By 21 days of age, an acute dose of haloperidol induced a cataleptic response similar to that described for adult animals. Following 7 days of repeated haloperidol administration, the cataleptogenic effects of haloperidol were attenuated in animals aged 21 days and older, but not in 8- and 14-day-old rats. Subjects were sacrificed 70 min after the injection of the test dose of haloperidol or saline and the corpus striatum and olfactory tubercles were dissected for HPLC determination of dopamine (DA) and its metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC). In the corpus striatum, an area believed to be important for DA-related catalepsy, acute and repeated haloperidol induced a slight increase in concentrations of HVA in 8-day-old rats, and an increase in both DOPAC and HVA concentrations in animals aged 14 days and older. Tolerance after repeated haloperidol administration, in the form of an attenuation of the haloperidol-induced increase in DA metabolites, was not apparent until 35 days of age. These data contrast with the behavioral data, which indicate that the ability to develop a tolerance to the cataleptogenic effects of haloperidol matures by 21 days of age. The pattern of responses in the olfactory tubercles differed from those observed in the striatum. Following acute haloperidol, subjects did not show any increase in HVA until 14 days of age, and in both HVA and DOPAC until 21 days of age. At no age, including adults, was one week of repeated administration of haloperidol sufficient to induce tolerance to the effects of haloperidol on DA metabolites in the olfactory tubercles. In addition to providing information about the development of certain aspects of DA systems in rats, these studies suggest that an attenuation of the haloperidol-induced increase in DA metabolites is not necessary for the development of tolerance to haloperidol-induced catalepsy.