Influence of intravenous administration of the antipsychotic drug benperidol on the QT interval

A group effect is generally assumed regarding the prolongation of the QT interval through butyrophenone antipsychotics like haloperidol. Consequently intravenous administration of benperidol is seen critically notwithstanding sparse evidence; thus benperidol and haloperidol were compared regarding their cardiac risk of prolonging the QT interval when administered intravenously for acute sedation of psychotic patients. The QT interval was measured by a 12-lead ECG. For the correction of QT values Bazett's formula was used. The resulting QTc intervals of the benperidol and the haloperidol group were compared using Mann-Whitney U-test. Our data provide statistical evidence for benperidol being less prone to cause QTc prolongation than haloperidol (p = 0.049). The results of our study indicate a more favourable risk profile of benperidol compared to haloperidol regarding QTc prolongation when administered intravenously.

Analysis of pharmacology data and the prediction of adverse drug reactions and off-target effects from chemical structure

Preclinical Safety Pharmacology (PSP) attempts to anticipate adverse drug reactions (ADRs) during early phases of drug discovery by testing compounds in simple, in vitro binding assays (that is, preclinical profiling). The selection of PSP targets is based largely on circumstantial evidence of their contribution to known clinical ADRs, inferred from findings in clinical trials, animal experiments, and molecular studies going back more than forty years. In this work we explore PSP chemical space and its relevance for the prediction of adverse drug reactions. Firstly, in silico (computational) Bayesian models for 70 PSP-related targets were built, which are able to detect 93% of the ligands binding at IC(50) < or = 10 microM at an overall correct classification rate of about 94%. Secondly, employing the World Drug Index (WDI), a model for adverse drug reactions was built directly based on normalized side-effect annotations in the WDI, which does not require any underlying functional knowledge. This is, to our knowledge, the first attempt to predict adverse drug reactions across hundreds of categories from chemical structure alone. On average 90% of the adverse drug reactions observed with known, clinically used compounds were detected, an overall correct classification rate of 92%. Drugs withdrawn from the market (Rapacuronium, Suprofen) were tested in the model and their predicted ADRs align well with known ADRs. The analysis was repeated for acetylsalicylic acid and Benperidol which are still on the market. Importantly, features of the models are interpretable and back-projectable to chemical structure, raising the possibility of rationally engineering out adverse effects. By combining PSP and ADR models new hypotheses linking targets and adverse effects can be proposed and examples for the opioid mu and the muscarinic M2 receptors, as well as for cyclooxygenase-1 are presented. It is hoped that the generation of predictive models for adverse drug reactions is able to help support early SAR to accelerate drug discovery and decrease late stage attrition in drug discovery projects. In addition, models such as the ones presented here can be used for compound profiling in all development stages.

[Effect of activation tasks on acute neuroleptic-induced akathisia]

In this study, we investigated experimentally the effects of different activation procedures on both motor and psychic symptoms in of 11 in-patients with acute neuroleptic-induced akathisia using the Hillside and Barnes akathisia rating scales and videotape rating technique. Motor activation was achieved by finger tapping. Cognitive activation tasks consisted of sequences of mental calculations which were designed either to be easy to perform or to produce stress due to a given time limit or to more difficult calculation operations, respectively. Motor as well as psychic symptoms of akathisia decreased during both motor and simple cognitive activation without stress. By contrast, stress-producing calculation tasks led to an increase in motor and psychic symptoms immediately following the task performance. These possibly specific effects of activation procedures on symptoms might be useful in differentiating acute neuroleptic-induced akathisia from other neuroleptic-induced and extrapyramidal movement disorders.

[Leukopenia associated with butyrophenones. A successful treatment of psychoses with pulsed administration of neuroleptics]

In the monotherapeutic treatment of an acute schizophrenic psychoses with butyrophenones (haloperidol and benperidol) we saw immediate leucopenic reactions when the medication was given every day. In literature the risk of butyrophenone-induced blood dyscrasias seems to be underestimated. Therefore we decided to report this single case evaluation. When benperidol (short elimination--half life period) was given every other day ("interval-therapy") the blood cell count of the leucocytes normalized. Furthermore, the amount of psychopathological abnormalities measured by the Brief Psychiatric Rating Scale decreased under this intermittent treatment.

[123I]IBZM SPECT in patients treated with typical and atypical neuroleptics: relationship to drug plasma levels and extrapyramidal side effects

[123I]Iodobenzamide (IBZM) is an iodine-labeled dopamine receptor ligand and can be used to visualize brain D2 receptors in humans with single photon emission computerized tomography (SPECT). The ratio of striatal IBZM uptake to uptake in frontal cortex (ST/FC ratio) represents a semiquantitative measure of D2 receptor binding in the striatum. Our study sample included six patients treated with haloperidol (3.0-8.0 mg/day orally; one patient with an average of 0.9 mg/day intramuscularly), five patients with benperidol (9.0-15.0 mg/day orally) and nine patients treated with clozapine (200.0-600.0 mg/day orally). Typical neuroleptics (TNs) and atypical neuroleptics (ANs) were significantly different in their ST/FC ratios. The ST/FC ratios indicated that patients treated with benperidol exhibited the lowest ST/FC ratios, with increasingly higher ratios in patients on haloperidol or clozapine. We found a curvilinear relationship between the ST/FC ratios and the dose/kg body wt. of TNs and ANs on the basis of a dose-normalization according to Ki-values of the neuroleptic at D2 receptors and a weaker, but also curvilinear relationship between ST/FC ratios and normalized dosages according to clinically defined chlorpromazine equivalents. The specific uptake of IBZM did not correlate with the plasma levels of the TN haloperidol at the present dose range (0-12.4 ng/ml). For clozapine, a meaningful negative correlation between plasma levels and ST/FC ratio could be established. There was a negative continuous correlation between uptake of IBZM and extrapyramidal side effects, which is different from the threshold-based relationship between extrapyramidal side effects and IBZM uptake reported previously.

Gender differences in D2 dopamine receptor binding in drug-naive patients with schizophrenia: an [123I]iodobenzamide single photon emission computed tomography study

Recent studies have described a left lateralized striatal asymmetry of D2 dopamine receptors in male patients with schizophrenia. To replicate this finding and to explore its potential functional consequences, we investigated the D2 dopamine receptor system in 23 drug-naive patients with schizophrenia using single photon emission computed tomography (SPECT). Patients were examined in the drug-naive state and 72 h after completing a standardized neuroleptic treatment with benperidol (12-16 mg/day) for 25 days. Each SPECT examination comprised two scans: the first scan was taken 2 h after intravenous injection of 185 MBq [123I]iodobenzamide. After completion of the first scan, patients received benperidol (8 mg) intravenously. The second scan was started 20 min later. For analysis, basal ganglia to frontal cortex ratios were calculated. Fifteen of the 23 patients originally recruited completed the study on day 28. When compared to female patients, male patients showed a left lateralized asymmetry of striatal D2 dopamine receptor binding in the drug-naive state with an almost significant (P = 0.07) sex x hemisphere interaction. In the male patients, benperidol challenge led to a reversal of asymmetry patterns. These findings support previous reports of a left lateralized striatal D2 receptor binding in drug-naive male patients with schizophrenia and suggest that this asymmetry may affect the binding of conventional neuroleptics such as benperidol at the D2 dopamine receptor.

Imaging of dopamine receptors with [123I]iodobenzamide single-photon emission-computed tomography in neuroleptic malignant syndrome

With the tracer [123I]iodobenzamide ([123I]-IBZM), it is possible to image dopamine receptor occupancy with single-photon emission-computed tomography (SPECT). We report follow-up examinations with IBZM-SPECT in neuroleptic malignant syndrome (NMS) to display D2-receptor availability in the acute phase and during the course of remission. A 27-year-old man was admitted with severe akinesia, rigor, tachycardia, fever, and elevated creatine phosphokinase level (CK) after neuroleptic medication. NMS was diagnosed, and treatment was started with dantrolene, amantadine, and dopamine agonists. IBZM-SPECT examination was performed on days 6, 34, 90, 107, 131, and 201. In the acute state of NMS, there was no binding of IBZM to D2-receptors. SPECT reached almost normal values on day 131, but clinical examination still showed a mild parkinsonian syndrome. With SPECT, the D2-receptor occupancy in NMS could be successfully shown in correlation with extrapyramidal signs. IBZM-SPECT may therefore serve to monitor D2-receptor occupancy in patients at risk for NMS.

[The neuroleptic malignant syndrome]

HISTORY AND CLINICAL FINDINGS

A 22-year-old oligophrenic patient had on several occasions over several months been given various neuroleptics (haloperidol, benperidol, levomepromazine) for exacerbations of paranoid schizophrenia. For a few days before hospitalization he had become quiet and withdrawn, but on the day of admission 100 mg chlorprothixene was administered intramuscularly when he had become agitated. At admission he was somnolent, his general condition was disturbed. He had hyperhidrosis and hypersalivation, as well as tachycardia (112/min) with a normal body temperature of 37.8 degrees C. He also exhibited the cogwheel phenomenon of the limbs and neck, as well as tremor of the hands. The differential diagnosis included inflammatory disease of the brain, sinus thrombosis and, especially, malignant neuroleptic syndrome and febrile catatonia.

INVESTIGATIONS

The activities of creatine kinase (3840 U/l), GOT (75 U/l) and GPT (88 U/l) were all increased. Serum myoglobin was 77 micrograms/l. CSF contained blood and there was pleocytosis of 50/3 cells. The ECG showed sinus tachycardia. EEG, chest radiogram, computed tomography, magnetic resonance imaging and cerebral angiography showed no abnormalities. Febrile catatonia could not be excluded.

TREATMENT AND COURSE

4 hours after admission the patient began to respond with normal orientation. Shortly afterwards he was able to walk a few steps, i.e. there was no catatonia. But rigor, tremor, hypersalivation and tachycardia persisted and 12 hours later he developed a fever (up to 39.2 degrees C). Blood pressure varied with peak pressures up to 190/110 mm Hg. After 2 days muscle tone had clearly increased so much that voluntary movement was hardly possible. After amantadine administration (200 mg daily) the rigor improved and for the first time body temperature became normal again. There were no signs pointing to psychotic symptoms.

CONCLUSION

Neuroleptic malignant syndrome is difficult to distinguish from febrile catatonia and the diagnosis can often only be made through the clinical course.

Pharmacokinetics and bioavailability of benperidol in schizophrenic patients after intravenous and two different kinds of oral application

Pharmacokinetics and bioavailability of benperidol were determined in 13 schizophrenic patients after acute administration of 6 mg benperidol as an intravenous (i.v.) bolus injection, orally as liquid, and orally as tablets using a partially randomized cross-over design. Drug plasma levels were determined by high performance liquid chromatography with electrochemical detection and subjected to model independent pharmacokinetic analyses. After i.v. dosing the geometric means (mean-g) were 3.2 min for the distribution half-life, 5.80 h for the elimination half-life (t1/2 beta), 4.21 l/kg for the distribution volume, 7.50 h for the mean residence time (MRT), and 0.50 l/(h*kg) for the clearance. After oral administration as liquid and as tablet mean-g data for the time lag until the first appearance of measurable plasma concentrations were 0.33 and 1.1 h, mean-g t1/2 beta values were 5.5 and 4.7 h, respectively, mean-g tmax data were 1.0 h and 2.7 h, mean-g MRT values were 8.44 and 8.84 h, and mean-g Cmax maxvalues were 10.2 and 7.3 ng/ml. Differences between liquid and tablet administration were statistically significant for time lag, tmax, and Cmax. Mean-g absolute bioavailabilities were computed as 48.6% after liquid and 40.2% after tablet administration respectively. All parameters studied exhibited large intersubject variation. The plasma concentrations of the presumed metabolite "reduced benperidol" were found to be very low.

[Hypothermia caused by neuroleptics. 2 case reports and review of the literature]

The present paper discusses appearance and course of neuroleptic induced hypothermia of a 36 years old woman suffering from periodic catatonia and a 38 years old seriously mentally handicapped man. Analysis of clinical studies and pharmacological tests with animals about body temperature changes caused by neuroleptics yields that these may lead to hypothermia as well as hyperthermia, depending on individual disposition and dose, which is mainly a result of their effect through dopaminergic neurons of the hypothalamus, which controls thermoregulation, and of their influence on vasomotoric mechanisms of vessels of the skin. Though hyperthermic changes are more hazardous and occur more frequently hypothermia by neuroleptic agents is clinically relevant as shown by the summarizing presentation of previously released case reports: hypothermia is found at neuroleptic medicated healthy volunteers and at psychiatric patients with or without physical illness, at which hypothyreosis and impair of the brain seem to represent special risks.

Correct titration of non-drugs and some other methodological issues

Doctors' prescription and dosing behaviour was investigated using data from 9 clinical trials in 550 patients treated with psychotropics. 7 trials were conducted under double- and 2 under single-blind conditions. In 3 of these trials, oral and i.m. preparations were used demanding a double-dummy design. All patients were evaluated on a weekly or 2-week basis using psychopathological rating scales (i.e. Hamilton Anxiety Scale, Hamilton Depression Scale, Clinical Global Impressions, Simpson and Angus EPS). It was found that (a) oral-medication titration was 3- to 4-fold more broad-ranging than i.m. medication titration, (b) oral placebo was titrated to the same extent as the oral investigational drugs, and (c) the titration schedule did not follow protocol requirements. Moreover, the average doses in all drug and placebo groups were the same. Concomitant medication like sleep inducers was found to be more closely related to doctors' habits than to actual medical need. Independent of trial and investigational drug, 10-33% of all patients received additional sleep inducers.

[Neuroleptic malignant syndrome--a case report on diagnosis, differential diagnosis and therapy of a life threatening complication of treatment with neuroleptics]

The neuroleptic malignant syndrome is a potentially lethal consequence of treatment with neuroleptics. It is possible that a patient, suffering from neuroleptic malignant syndrome now, had no such illness in the past, while being treated with neuroleptics; furthermore he may respond well to rechallenge with the original agent in the future. The malignant neuroleptic syndrome of a 29 year old man, whom we treated with benperidole, is described. The course of the disease and the differential-diagnosis is stated. The ways of treatment with bromocriptine, dantrolene sodium and amantadine, as described in the literature, are presented. As the neuroleptic malignant syndrome ist rare many cases should be collected in order to enhance the knowledge of the etiology and the pathogenesis of that life--threatening complication of treatment with neuroleptic drugs.