Pharmacokinetics of haloperidol: an update

Stereoselective synthesis of O-tosyl azabicyclic derivatives via aza Prins reaction of endocyclic N-acyliminium ions: application to the total synthesis of (±)-epi-indolizidine 167B and 209D

A diastereoselective synthesis of 4-O-tosyl piperidine containing azabicyclic derivatives has been established via Prins cyclization reaction. This protocol has been applied for the total synthesis of (±)-epi-indolizidine 167B and 209D.

Population pharmacokinetic-pharmacodynamic modeling of haloperidol in patients with schizophrenia using positive and negative syndrome rating scale

The aim of this study was to develop a pharmacokinetic-pharmacodynamic (PKPD) model that quantifies the efficacy of haloperidol, accounting for the placebo effect, the variability in exposure-response, and the dropouts. Subsequently, the developed model was utilized to characterize an effective dosing strategy for using haloperidol as a comparator drug in future antipsychotic drug trials. The time course of plasma haloperidol concentrations from 122 subjects and the Positive and Negative Syndrome Scale (PANSS) scores from 473 subjects were used in this analysis. A nonlinear mixed-effects modeling approach was utilized to describe the time course of PK and PANSS scores. Bootstrapping and simulation-based methods were used for the model evaluation. A 2-compartment model adequately described the haloperidol PK profiles. The Weibull and Emax models were able to describe the time course of the placebo and the drug effects, respectively. An exponential model was used to account for dropouts. Joint modeling of the PKPD model with dropout model indicated that the probability of patients dropping out is associated with the observed high PANSS score. The model evaluation results confirmed that the precision and accuracy of parameter estimates are acceptable. Based on the PKPD analysis, the recommended oral dose of haloperidol to achieve a 30% reduction in PANSS score from baseline is 5.6 mg/d, and the corresponding steady-state effective plasma haloperidol exposure is 2.7 ng/mL. In conclusion, the developed model describes the time course of PANSS scores adequately, and a recommendation of haloperidol dose was derived for future antipsychotic drug trials.

Antifungal application of nonantifungal drugs

Candida species are the cause of 60% of all mycoses in immunosuppressed individuals, leading to ∼150,000 deaths annually due to systemic infections, whereas the current antifungal therapies either have toxic side effects or are insufficiently efficient. We performed a screening of two compound libraries, the Enzo and the Institute for Molecular Medicine Finland (FIMM) oncology collection library, for anti-Candida activity based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. From a total of 844 drugs, 26 agents showed activity against Candida albicans. Of those, 12 were standard antifungal drugs (SADs) and 7 were off-target drugs previously reported to be active against Candida spp. The remaining 7 off-target drugs, amonafide, tosedostat, megestrol acetate, melengestrol acetate, stanozolol, trifluperidol, and haloperidol, were identified with this screen. The anti-Candida activities of the new agents were investigated by three individual assays using optical density, ATP levels, and microscopy. The antifungal activities of these drugs were comparable to those of the SADs found in the screen. The aminopeptidase inhibitor tosedostat, which is currently in a clinical trial phase for anticancer therapy, displayed a broad antifungal activity against different Candida spp., including Candida glabrata. Thus, this screen reveals agents that were previously unknown to be anti-Candida agents, which allows for the design of novel therapies against invasive candidiasis.

Effect of intravenous haloperidol on the duration of delirium and coma in critically ill patients (Hope-ICU): a randomised, double-blind, placebo-controlled trial

BACKGROUND

Delirium is frequently diagnosed in critically ill patients and is associated with poor clinical outcomes. Haloperidol is the most commonly used drug for delirium despite little evidence of its effectiveness. The aim of this study was to establish whether early treatment with haloperidol would decrease the time that survivors of critical illness spent in delirium or coma.

METHODS

We did this double-blind, placebo-controlled randomised trial in a general adult intensive care unit (ICU). Critically ill patients (≥18 years) needing mechanical ventilation within 72 h of admission were enrolled. Patients were randomised (by an independent nurse, in 1:1 ratio, with permuted block size of four and six, using a centralised, secure web-based randomisation service) to receive haloperidol 2.5 mg or 0.9% saline placebo intravenously every 8 h, irrespective of coma or delirium status. Study drug was discontinued on ICU discharge, once delirium-free and coma-free for 2 consecutive days, or after a maximum of 14 days of treatment, whichever came first. Delirium was assessed using the confusion assessment method for the ICU (CAM-ICU). The primary outcome was delirium-free and coma-free days, defined as the number of days in the first 14 days after randomisation during which the patient was alive without delirium and not in coma from any cause. Patients who died within the 14 day study period were recorded as having 0 days free of delirium and coma. ICU clinical and research staff and patients were masked to treatment throughout the study. Analyses were by intention to treat. This trial is registered with the International Standard Randomised Controlled Trial Registry, number ISRCTN83567338.

FINDINGS

142 patients were randomised, 141 were included in the final analysis (71 haloperidol, 70 placebo). Patients in the haloperidol group spent about the same number of days alive, without delirium, and without coma as did patients in the placebo group (median 5 days [IQR 0-10] vs 6 days [0-11] days; p=0.53). The most common adverse events were oversedation (11 patients in the haloperidol group vs six in the placebo group) and QTc prolongation (seven patients in the haloperidol group vs six in the placebo group). No patient had a serious adverse event related to the study drug.

INTERPRETATION

These results do not support the hypothesis that haloperidol modifies duration of delirium in critically ill patients. Although haloperidol can be used safely in this population of patients, pending the results of trials in progress, the use of intravenous haloperidol should be reserved for short-term management of acute agitation.

FUNDING

National Institute for Health Research.

A naturalistic comparison of the efficacy and safety of intramuscular olanzapine and intramuscular levomepromazine in agitated elderly patients with schizophrenia

BACKGROUND

There have not been any reports in Japan clarifying the efficacy and safety of intramuscular (IM) olanzapine and IM levomepromazine in agitated elderly patients with schizophrenia. This study was a comparative investigation of the clinical efficacy and safety of IM olanzapine and IM levomepromazine in agitated elderly patients with schizophrenia at 2 hours post-dose.

METHODS

The subjects were 52 inpatients who were diagnosed with schizophrenia according to the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV. Their clinical symptoms were assessed using the Positive and Negative Syndrome Scale Excited Component (PANSS-EC), PANSS, and Agitation Calmness Evaluation Scale (ACES), and their safety was assessed using the Abnormal Involuntary Movement Scale (AIMS), Barnes Akathisia Rating Scale (BARS), Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS), and glucose test.

RESULTS

The PANSS-EC total score, the ACES score, and the glucose level significantly decreased from baseline in both the IM olanzapine group and the levomepromazine injection group; however, no between-group differences were observed. Mean change from baseline in the PANSS total score, positive score, the BARS score, and the DIEPSS total score was significantly greater in the IM olanzapine injection group compared with the levomepromazine injection group.

CONCLUSION

The results of this study suggest that agitated elderly patients rapidly respond to IM olanzapine and IM levomepromazine treatment. Furthermore, these results suggest that IM olanzapine is safer than IM levomepromazine and causes greater improvement in positive symptoms.

Significance of reductive metabolism in human intestine and quantitative prediction of intestinal first-pass metabolism by cytosolic reductive enzymes

The number of new drug candidates that are cleared via non-cytochrome P450 (P450) enzymes has increased. However, unlike oxidation by P450, the roles of reductive enzymes are less understood. The metabolism in intestine is especially not well known. The purposes of this study were to investigate the significance of reductive metabolism in human intestine, and to establish a quantitative prediction method of intestinal first-pass metabolism by cytosolic reductive enzymes, using haloperidol, mebendazole, and ziprasidone. First, we estimated the metabolic activities for these compounds in intestine and liver using subcellular fractions. Metabolic activities were detected in human intestinal cytosol (HIC) for all three compounds, and the intrinsic clearance values were higher than those in human liver cytosol for haloperidol and mebendazole. These metabolic activities in HIC were NADPH- and/or NADH-dependent. Furthermore, the metabolic activities for all three compounds in HIC were largely inhibited by menadione, which has been used as a carbonyl reductase (CBR)-selective chemical inhibitor. Therefore, considering subcellular location, cofactor requirement, and chemical inhibition, these compounds might be metabolized by CBRs in human intestine. Subsequently, we tried to quantitatively predict intestinal availability (F(g)) for these compounds using human intestinal S9 (HIS9). Our prediction model using apparent permeability of parallel artificial membrane permeability assay and metabolic activities in HIS9 could predict F(g) in humans for the three compounds well. In conclusion, CBRs might have higher metabolic activities in human intestine than in human liver. Furthermore, our prediction method of human F(g) using HIS9 is applicable to substrates of cytosolic reductive enzymes.

Therapeutic drug monitoring of common antipsychotics

The aim of this review is to provide information for interpreting outcome results from monitoring of antipsychotics in biological samples. A brief overview of the working mechanisms, pharmacological effects, drug interactions, and analytical methods of classical and atypical antipsychotics is given. Nineteen antipsychotics were selected based on their importance in the worldwide market as follows: amisulpride, aripiprazole, asenapine, bromperidol, clozapine, flupenthixol, haloperidol, iloperidone, lurasidone, olanzapine, paliperidone, perphenazine, pimozide, pipamperone, quetiapine, risperidone, sertindole, sulpiride, and zuclopenthixol. A straightforward relationship between administered dose, plasma or serum concentration, clinical outcome, or adverse effects is often lacking. Nowadays, focus lies on therapeutic drug monitoring and individualized therapy to find adequate treatment, to explain treatment failure or nonresponse, and to check patient compliance. However, extensive research in this field is still mandatory.

Psychotropic drug-drug interactions involving P-glycoprotein

Multidrug resistance P-glycoprotein (P-gp; also known as MDR1 and ABCB1) is expressed in the luminal membrane of the small intestine and blood-brain barrier, and the apical membranes of excretory cells such as hepatocytes and kidney proximal tubule epithelia. P-gp regulates the absorption and elimination of a wide range of compounds, such as digoxin, paclitaxel, HIV protease inhibitors and psychotropic drugs. Its substrate specificity is as broad as that of cytochrome P450 (CYP) 3A4, which encompasses up to 50 % of the currently marketed drugs. There has been considerable interest in variations in the ABCB1 gene as predictors of the pharmacokinetics and/or treatment outcomes of several drug classes, including antidepressants and antipsychotics. Moreover, P-gp-mediated transport activity is saturable, and is subject to modulation by inhibition and induction, which can affect the pharmacokinetics, efficacy or safety of P-gp substrates. In addition, many of the P-gp substrates overlap with CYP3A4 substrates, and several psychotropic drugs that are P-gp substrates are also CYP3A4 substrates. Therefore, psychotropic drugs that are P-gp substrates may cause a drug interaction when P-gp inhibitors and inducers are coadministered, or when psychotropic drugs or other medicines that are P-gp substrates are added to a prescription. Hence, it is clinically important to accumulate data about drug interactions through studies on P-gp, in addition to CYP3A4, to assist in the selection of appropriate psychotropic medications and in avoiding inappropriate combinations of therapeutic agents. There is currently insufficient information available on the psychotropic drug interactions related to P-gp, and therefore we summarize the recent clinical data in this review.

Parkinsonism in elderly users of haloperidol: associated with dose, plasma concentration, and duration of use

Factors that influence the variation in occurrence of antipsychotic-induced parkinsonism (AIP) in the elderly have not been well elucidated. The aim of this study was to investigate the association between parkinsonism in elderly users of haloperidol and prescribed dose, plasma concentration, and duration of use of haloperidol in a cross-sectional design. This study included 150 inpatients aged 65 years and older who were treated with haloperidol. Parkinsonism assessed by the Simpson Angus Scale was present in 46% of the included patients. Prescribed haloperidol dose varied from 0.3 to 5 mg/d. Plasma concentration ranged from 0.13 to 4.11 μg/L, with one outlying measurement (21.43 μg/L). Dose is moderate but significantly associated with haloperidol plasma concentration (weighted R2 = 0.32; P < 0.001). Variability in the total score on the Simpson Angus Scale could not be explained by the variability in dose, concentration (respectively R2 = 0.003 and 0.001) nor duration of use of haloperidol. Smoking showed to be not significantly protective in the development of AIP (crude odds ratio, 0.39; 95% confidence interval, 0.15-0.997; and adjusted odds ratio, 0.44; 95% confidence interval, 0.17-1.17). In a clinical practice-setting dose, neither plasma concentration nor duration of use of haloperidol is associated with an increased occurrence of AIP. This study does not support the hypothesis of the peripheral pharmacokinetic explanation for the high prevalence of AIP and differences in AIP sensitivity in the elderly during treatment with haloperidol.

Clinically significant psychotropic drug-drug interactions in the primary care setting

In recent years, the growing numbers of patients seeking care for a wide range of psychiatric illnesses in the primary care setting has resulted in an increase in the number of psychotropic medications prescribed. Along with the increased utilization of psychotropic medications, considerable variability is noted in the prescribing patterns of primary care providers and psychiatrists. Because psychiatric patients also suffer from a number of additional medical comorbidities, the increased utilization of psychotropic medications presents an elevated risk of clinically significant drug interactions in these patients. While life-threatening drug interactions are rare, clinically significant drug interactions impacting drug response or appearance of serious adverse drug reactions have been documented and can impact long-term outcomes. Additionally, the impact of genetic variability on the psychotropic drug's pharmacodynamics and/or pharmacokinetics may further complicate drug therapy. Increased awareness of clinically relevant psychotropic drug interactions can aid clinicians to achieve optimal therapeutic outcomes in patients in the primary care setting.

The blood concentration and organ distribution of haloperidol at therapeutic and toxic doses in severe fatty liver disease

The aim of this study was to investigate the difference between the pharmacokinetics of haloperidol in normal rats and in rats with fatty liver disease. A therapeutic dosage (0.1 mg/kg) and a toxic dose (15 mg/kg) of haloperidol were administrated to normal 9-week-old male rats or those with severe fatty liver disease, and the blood concentration of haloperidol was determined 15 min, 1, 2, and 3 h following haloperidol administration. The concentration of haloperidol in the organs was determined 1, 2, and 3 h after the haloperidol administration. Additionally, the volume of the portal vein blood flow was measured 3 h after haloperidol administration. When given at the therapeutic dosage, the concentrations of haloperidol in both the blood and organs of the rats with fatty liver disease were significantly higher than those in the normal rats. However, when given at the toxic level, the blood and organ haloperidol concentrations 1 h after administration tended to be lower in the rats with fatty liver disease than those in the normal rats; these lower haloperidol levels returned to be the levels in the normal rats 3 h after the administration of haloperidol. The volume of the portal vein blood flow significantly increased following the toxic haloperidol dose as compared with the volume pre-administration and following the therapeutic haloperidol dose in the normal rats. However, the volume did not change after the toxic or the therapeutic dose of haloperidol compared with pre-administration in rats with severe fatty liver disease, although it was significantly higher than in the normal rats. The pathway for haloperidol metabolism might have been saturated before the administration of haloperidol in rats with fatty liver disease; thus, it is possible that the blood concentration of haloperidol tends to be much higher in individuals with severe fatty liver disease than in those with normal livers in an inverse proportion to the dosage of haloperidol.

Human UDP-glucuronosyltransferase isoforms involved in haloperidol glucuronidation and quantitative estimation of their contribution

A major metabolic pathway of haloperidol is glucuronidation catalyzed by UDP-glucuronosyltransferase (UGT). In this study, we found that two glucuronides were formed by the incubation of haloperidol with human liver microsomes (HLM) and presumed that the major and minor metabolites (>10-fold difference) were O- and N-glucuronide, respectively. The haloperidol N-glucuronidation was catalyzed solely by UGT1A4, whereas the haloperidol O-glucuronidation was catalyzed by UGT1A4, UGT1A9, and UGT2B7. The kinetics of the haloperidol O-glucuronidation in HLM was monophasic with K(m) and V(max) values of 85 μM and 3.2 nmol · min⁻¹ · mg⁻¹, respectively. From the kinetic parameters of the recombinant UGT1A4 (K(m) = 64 μM, V(max) = 0.6 nmol · min⁻¹ · mg⁻¹), UGT1A9 (K(m) = 174 μM, V(max) = 2.3 nmol · min⁻¹ · mg⁻¹), and UGT2B7 (K(m) = 45 μM, V(max) = 1.0 nmol · min⁻¹ · mg⁻¹), we could not estimate which isoform largely contributes to the reaction. Because the haloperidol O-glucuronidation in a panel of 17 HLM was significantly correlated (r = 0.732, p < 0.01) with zidovudine O-glucuronidation, a probe activity of UGT2B7, and the activity in the pooled HLM was prominently inhibited (58% of control) by gemfibrozil, an inhibitor of UGT2B7, we surmised that the reaction would mainly be catalyzed by UGT2B7. We could successfully estimate, using the concept of the relative activity factor, that the contributions of UGT1A4, UGT1A9, and UGT2B7 in HLM were approximately 10, 20, and 70%, respectively. The present study provides new insight into haloperidol glucuronidation, concerning the causes of interindividual differences in the efficacy and adverse reactions or drug-drug interactions.

Pharmacological and nonpharmacological management of delirium in critically ill patients

Delirium is a common yet under-diagnosed syndrome of acute brain dysfunction, which is characterized by inattention, fluctuating mental status, altered level of consciousness, or disorganized thinking. Although our recognition of risk factors for delirium has progressed, our understanding of the underlying pathophysiologic mechanisms remains limited. Improvements in monitoring and assessment for delirium (particularly in the intensive care setting) have resulted in validated and reliable tools such as arousal scales and bedside delirium monitoring instruments. Once delirium is recognized and the modifiable risk factors are addressed, the next step in management (if delirium persists) is often pharmacological intervention. The sedatives, analgesics, and hypnotics most often used in the intensive care unit (ICU) to achieve patient comfort are all too frequently deliriogenic, resulting in a longer duration of ICU and hospital stay, and increased costs. Therefore, identification of safe and efficacious agents to reduce the incidence, duration, and severity of ICU delirium is a hot topic in critical care. Recognizing that there are no medications approved by the Food and Drug Administration (FDA) for the prevention or treatment of delirium, we chose anti-psychotics and alpha-2 agonists as the general pharmacological focus of this article because both were subjects of relatively recent data and ongoing clinical trials. Emerging pharmacological strategies for addressing delirium must be combined with nonpharmacological approaches (such as daily spontaneous awakening trials and spontaneous breathing trials) and early mobility (combined with the increasingly popular approach called: Awakening and Breathing Coordination, Delirium Monitoring, Early Mobility, and Exercise [ABCDE] of critical care) to develop evidence-based approaches that will ensure safer and faster recovery of the sickest patients in our healthcare system.

Role of Haloperidol in Palliative Medicine

Haloperidol is a butyrophenone neuroleptic agent characterized as a high-affinity dopamine antagonist, originally used for the treatment of schizophrenia. Awareness of the role dopamine plays in many symptoms in palliative care, such as nausea, vomiting, and delirium, has led to the use of dopamine antagonists such as haloperidol for the treatment of these symptoms in the palliative care setting. Listed as 1 of the 25 important drugs in palliative care, haloperidol can be administered by multiple routes and can be given without dose alteration in the setting of both renal and hepatic insufficiency. Haloperidol is extensively metabolized in the liver, with CYP3A4 the chief cytochrome oxidase responsible for metabolism. This article will review the pharmacology, pharmacokinetics, and current uses of haloperidol in palliative medicine. There will be an examination of the evidence base for the use of haloperidol in palliative medicine.

Treating nausea and vomiting in palliative care: a review

Nausea and vomiting are portrayed in the specialist palliative care literature as common and distressing symptoms affecting the majority of patients with advanced cancer and other life-limiting illnesses. However, recent surveys indicate that these symptoms may be less common and bothersome than has previously been reported. The standard palliative care approach to the assessment and treatment of nausea and vomiting is based on determining the cause and then relating this back to the "emetic pathway" before prescribing drugs such as dopamine antagonists, antihistamines, and anticholinergic agents which block neurotransmitters at different sites along the pathway. However, the evidence base for the effectiveness of this approach is meager, and may be in part because relevance of the neuropharmacology of the emetic pathway to palliative care patients is limited. Many palliative care patients are over the age of 65 years, making these agents difficult to use. Greater awareness of drug interactions and QT(c) prolongation are emerging concerns for all age groups. The selective serotonin receptor antagonists are the safest antiemetics, but are not used first-line in many countries because there is very little scientific rationale or clinical evidence to support their use outside the licensed indications. Cannabinoids may have an increasing role. Advances in interventional gastroenterology are increasing the options for nonpharmacological management. Despite these emerging issues, the approach to nausea and vomiting developed within palliative medicine over the past 40 years remains relevant. It advocates careful clinical evaluation of the symptom and the person suffering it, and an understanding of the clinical pharmacology of medicines that are available for palliating them.

In vivo binding of antipsychotics to D3 and D2 receptors: a PET study in baboons with [11C]-(+)-PHNO

Measuring the in vivo occupancy of antipsychotic drugs at dopamine D(2) and D(3) receptors separately has been difficult because of the lack of selective radiotracers. The recently developed [(11)C]-(+)-PHNO is D(3)-preferring, allowing estimates of the relative D(2) and D(3) binding of antipsychotic drugs. We used positron emission tomography (PET) imaging in baboons with [(11)C]-(+)-PHNO to examine the binding of clozapine and haloperidol to D(2) and D(3) receptors. Four animals were scanned with dynamically acquired PET and arterial plasma input functions. Test and retest scans were acquired in single scanning sessions for three subjects to assess the reproducibility of [(11)C]-(+)-PHNO scans. Four additional scans were acquired in each of three subjects following single doses of antipsychotic drugs (clozapine 0.5534 mg/kg, haloperidol 0.0109 mg/kg, two administrations per drug per subject) and compared with baseline scans. The percent change in binding (ΔBP(ND)) following challenges with antipsychotic drugs was measured. A regression model, based on published values of regional D(2) and D(3) fractions of [(11)C]-(+)-PHNO BP(ND) in six brain regions, was used to infer occupancy at D(2) and D(3) receptors. BP(ND) following antipsychotic challenge decreased in all regions. Estimated D(2) : D(3) selectivity was 2.38 for haloperidol and 5.25 for clozapine, similar to published in vitro values for haloperidol (3.03), but slightly higher for clozapine (2.82). These data suggest that acute doses of clozapine and haloperidol bind to D(3) receptors in vivo, and that the lack of D(3) occupancy by antipsychotics observed in some recent imaging studies may be because of other phenomena.

Anti-emetic drugs in oncology: pharmacology and individualization by pharmacogenetics

OBJECTIVE

Nausea and vomiting are the most distressful side effects of cytotoxic drugs in cancer patients. Antiemetics are commonly used to reduce these side effects. However, the current antiemetic efficacy is about 70-80% in patients treated with highly-emetogenic cytotoxic drugs. One of the potential factors explaining this suboptimal response is variability in genes encoding enzymes and proteins which play a role in metabolism, transport and receptors related to antiemetic drugs. Aim of this review was to describe the pharmacology and pharmacogenetic concepts of of antiemetics in oncology.

METHOD

Pharmacogenetic and pharmacology studies of antiemetics in oncology published between January 1997 and February 2010 were searched in PubMed. Furthermore, related textbooks were also used for exploring the pharmacology of antiemetic drugs. The antiemetic drugs which were searched were the 5-hydroxytryptamine 3 receptor antagonists (5-HT3RAs), dopamine antagonists, corticosteroids, benzodiazepines, cannabinoids, antihistamines and neurokinin-1 antagonists.

RESULT

The 5-HT3RAs are widely used in highly emetogenic chemotherapy in combination with dexamethasone and a neurokinin-1 antagonist, especially in acute phase. However, the dopamine antagonists and benzodiazepines were found more appropriate for use in breakthrough and anticipatory symptoms or in preventing the delayed phase of chemotherapy induced nausea and vomiting. The use of cannabinoids and antihistamines need further investigation. Only six articles on pharmacogenetics of the 5-HT3RAs in highly emetogenic chemotherapy are published. Specifically, these studies investigated the association of the efficacy of 5-HT3RAs and variants in the multi drug resistance 1 (MDR1) gene, 5-HT3A,B and C receptor genes and CYP2D6 gene. The pharmacogenetic studies of the other antiemetics were not found in this review.

CONCLUSION

It is concluded that pharmacogenetic studies with antiemetics are sparse. It is too early to implement results of pharmacogenetic association studies of antiemetic drugs in clinical practice: confirmation of early findings is required.

Fentanyl, but not haloperidol, entrains persisting circadian activity episodes when administered at 24- and 31-h intervals

Administration of several drugs of abuse on a 24-h schedule has been shown to entrain both pre-drug (anticipatory) and post-drug (evoked) circadian activity episodes that persist for several days when the drug is withheld. The present study tested the entrainment effects of fentanyl, an opioid agonist with a noted abuse liability, and haloperidol, an anti-psychotic dopamine antagonist without apparent abuse liability. Adult female Sprague-Dawley rats housed under constant light in cages with attached running wheels received repeated low, medium, or high doses of either fentanyl or haloperidol on a 24-h administration schedule followed by a 31-h schedule (Experiment 1) or solely on a 31-h schedule (Experiment 2). The results showed that all three doses of fentanyl entrained both pre-drug and post-drug episodes of wheel running when administered every 24h, and the combined pre- and post-fentanyl activity episodes persisted for at least 3 days when the drug was withheld during test days. On the 31-h schedule, fentanyl produced an "ensuing" activity episode approximately 24h post-administration, but failed to produce an anticipatory episode 29-31h post-administration. In contrast, haloperidol injections failed to produce both pre-drug episodes on the 24-h schedule and circadian ensuing episodes on the 31-h schedule, and post-haloperidol suppression of activity appeared to mask the free-running activity rhythm. Taken together, these results provide additional evidence that drugs of abuse share a common ability to entrain circadian activity episodes.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Histone H3 phosphorylation is under the opposite tonic control of dopamine D2 and adenosine A2A receptors in striatopallidal neurons

The antipsychotic agent haloperidol regulates gene transcription in striatal medium spiny neurons (MSNs) by blocking dopamine D2 receptors (D2Rs). We examined the mechanisms by which haloperidol increases the phosphorylation of histone H3, a key step in the nucleosomal response. Using bacterial artificial chromosome (BAC)-transgenic mice that express EGFP under the control of the promoter of the dopamine D1 receptor (D1R) or the D2R, we found that haloperidol induced a rapid and sustained increase in the phosphorylation of histone H3 in the striatopallidal MSNs of the dorsal striatum, with no change in its acetylation. This effect was mimicked by raclopride, a selective D2R antagonist, and prevented by the blockade of adenosine A2A receptors (A2ARs), or genetic attenuation of the A2AR-associated G protein, Galpha(olf). Mutation of the cAMP-dependent phosphorylation site (Thr34) of the 32-kDa dopamine and cAMP-regulated phosphoprotein (DARPP-32) decreased the haloperidol-induced H3 phosphorylation, supporting the role of cAMP in H3 phosphorylation. Haloperidol also induced extracellular signal-regulated kinase (ERK) phosphorylation in striatopallidal MSNs, but this effect was not implicated in H3 phosphorylation. The levels of mitogen- and stress-activated kinase 1 (MSK1), which has been reported to mediate ERK-induced H3 phosphorylation, were lower in striatopallidal than in striatonigral MSNs. Moreover, haloperidol-induced H3 phosphorylation was unaltered in MSK1-knockout mice. These data indicate that, in striatopallidal MSNs, H3 phosphorylation is controlled by the opposing actions of D2Rs and A2ARs. Thus, blockade of D2Rs promotes histone H3 phosphorylation through the A2AR-mediated activation of Galpha(olf) and inhibition of protein phosphatase-1 (PP-1) through the PKA-dependent phosphorylation of DARPP-32.

Treatment of nausea and vomiting in terminally ill cancer patients

Nausea and vomiting is a common and distressing symptom complex in patients with far-advanced cancer, affecting up to 60% of individuals at some stage of their illness. The current approach to the palliative care of patients with nausea and vomiting is based on identifying the cause, understanding its pathophysiology and knowing the pharmacology of the drugs available for its amelioration. The following six main syndromes are identified: gastric stasis, biochemical, raised intracranial pressure, vestibular, mechanical bowel obstruction and ileus. A careful history, focused physical examination and appropriate investigations are needed to elucidate the syndrome and its cause, so that therapy is rational. Drugs are the mainstay of treatment in terminal cancer, and the main classes of antiemetic agents are prokinetics, dopamine antagonists, antihistamines, anticholinergics and serotonin antagonists. Dexamethasone and octreotide are also used, especially in bowel obstruction. Non-drug measures are important in relieving the associated distress. Patients should be able to die comfortably, without tubes. Despite decades of practice affirming this approach, the evidence base is weak and well designed studies are urgently needed.

Haloperidol and risperidone have specific effects on altered pain sensitivity in the ketamine model of schizophrenia

RATIONALE

The ketamine (ket) model reflects features of schizophrenia as well as secondary symptoms such as altered pain sensitivity.

OBJECTIVES

In the present study, we investigated the effect of subchronic oral treatment with haloperidol (hal, 0.075 mg/kg) and risperidone (ris, 0.2 mg/kg) on altered pain perception and locomotor activity in this model.

RESULTS

In reaction to 5 mg/kg morphine, ket pretreated animals showed a diminished analgesic response. Hal had no analgesic effect per se, but the compound normalised the analgesic reaction to morphine in the ket pretreated animals. The effect of ris was complex. First, there was no analgesic effect per se, and control animals showed a dose-dependent increase in the analgesic index after morphine injection. In the ket group treated with ris, the analgesic response to 5 mg/kg morphine was attenuated and in response to 10 mg/kg analgesia was comparable with that measured in controls. The reduced analgesic effect was not due to pharmacokinetic differences in morphine metabolism. After administration via drinking water in saline-injected control animals, the hal blood serum concentration was 2.6 +/- 0.45 ng/ml. In ket-injected animals, the mean serum concentration of hal amounted to 1.2 +/- 0.44 ng/ml. In the experiment using ris, animals in the control group had higher ris serum concentrations compared with ket-injected animals. In control animals, morphine dose dependently decreased locomotor activity. This effect was significantly stronger in the ket pretreated groups.

CONCLUSIONS

Hal and ris had different effects on altered pain sensitivity. It was hypothesised that these results are connected with alterations in dopamine D2 and mu opioid receptor binding.

Phospholipase C-beta1 knockout mice exhibit endophenotypes modeling schizophrenia which are rescued by environmental enrichment and clozapine administration

Phospholipase C-beta1 (PLC-beta1) is a rate-limiting enzyme implicated in postnatal-cortical development and neuronal plasticity. PLC-beta1 transduces intracellular signals from specific muscarinic, glutamate and serotonin receptors, all of which have been implicated in the pathogenesis of schizophrenia. Here, we present data to show that PLC-beta1 knockout mice display locomotor hyperactivity, sensorimotor gating deficits as well as cognitive impairment. These changes in behavior are regarded as endophenotypes homologous to schizophrenia-like symptoms in rodents. Importantly, the locomotor hyperactivity and sensorimotor gating deficits in PLC-beta1 knockout mice are subject to beneficial modulation by environmental enrichment. Furthermore, clozapine but not haloperidol (atypical and typical antipsychotics, respectively) rescues the sensorimotor gating deficit in these animals, suggesting selective predictive validity. We also demonstrate a relationship between the beneficial effects of environmental enrichment and levels of M1/M4 muscarinic acetylcholine receptor binding in the neocortex and hippocampus. Thus we have demonstrated a novel mouse model, displaying disruption of multiple postsynaptic signals implicated in the pathogenesis of schizophrenia, a relevant behavioral phenotype and associated gene-environment interactions.

Psychiatric issues in renal failure and dialysis

This article aims to bring to the fore, issues regarding the interface of psychiatry and renal failure. Depression, anxiety, suicide and delirium are common complications observed in patients with renal failure. Pharmacological management of these problems need stringent monitoring on part of the psychiatrist. This article examines the various complications that may be observed in patients with renal failure while discussing treatment approaches and also emphasizing the need for interdisciplinary team work in improving the quality of life of patients with renal failure and those on dialysis.

The aldo-keto reductase superfamily and its role in drug metabolism and detoxification

The aldo-keto reductase (AKR) superfamily comprises enzymes that catalyze redox transformations involved in biosynthesis, intermediary metabolism, and detoxification. Substrates of AKRs include glucose, steroids, glycosylation end-products, lipid peroxidation products, and environmental pollutants. These proteins adopt a (beta/alpha)(8) barrel structural motif interrupted by a number of extraneous loops and helixes that vary between proteins and bring structural identity to individual families. The human AKR family differs from the rodent families. Due to their broad substrate specificity, AKRs play an important role in the phase II detoxification of a large number of pharmaceuticals, drugs, and xenobiotics.

Peroneal nerve palsy due to compartment syndrome after facial plastic surgery

A 25-year-old white man, right after bilateral rhytidoplasty, presented with agitation, necessiting use of haloperidol. Some hours after, he developed severe pain in his legs and a diagnosis of neuroleptic malignant syndrome (NMS) was considered. Even with treatment for NMS he still complained of pain. A diagnosis of lower limb compartment syndrome (CS) was done only 12 hours after the initial event, being submitted to fasciotomy in both legs, disclosing very pale muscles, due to previous ischemia. This syndrome was not explained only by facial surgery, his position and duration of the procedure. It can be explained by a sequence of events. He had a history of pain in his legs during physical exercises, usually seen in chronic compartment syndrome. He used to take anabolizant and venlafaxine, not previously related, and the agitation could be related to serotoninergic syndrome caused by interaction between venlafaxine and haloperidol. Rhabdomyolisis could lead to oedema and ischmemia in both anterior leg compartment. This report highlights the importance of early diagnosis of compartment syndrome, otherwise, even after fasciotomy, a permanent disability secondary to peripheral nerve compression could occur.

A functional genetic polymorphism on human carbonyl reductase 1 (CBR1 V88I) impacts on catalytic activity and NADPH binding affinity

Human carbonyl reductase 1 (CBR1) metabolizes endogenous and xenobiotic substrates such as the fever mediator, prostaglandin E2 (PGE2), and the anticancer anthracycline drug, daunorubicin. We screened 33 CBR1 full-length cDNA samples from white and black liver donors and performed database analyses to identify genetic determinants of CBR1 activity. We pinpointed a single nucleotide polymorphism on CBR1 (CBR1 V88I) that encodes for a valine-to-isoleucine substitution for further characterization. We detected the CBR1 V88I polymorphism in DNA samples from individuals with African ancestry (p = 0.986, q = 0.014). Kinetic studies revealed that the CBR1 V88 and CBR1 I88 isoforms have different maximal velocities for daunorubicin (V(max) CBR1 V88, 181 +/- 13 versus V(max) CBR1 I88, 121 +/- 12 nmol/min . mg, p < 0.05) and PGE2 (V(max) CBR1 V88, 53 +/- 7 versus V(max) CBR1 I88, 35 +/- 4 nmol/min . mg, p < 0.01). Concomitantly, CBR1 V88 produced higher levels of the cardiotoxic metabolite daunorubicinol compared with CBR1 I88 (1.7-fold, p < 0.0001). Inhibition studies demonstrated that CBR1 V88 and CBR1 I88 are distinctively inhibited by the flavonoid, rutin (IC50 CBR1 V88, 54.0 +/- 0.4 microM versus IC50 CBR1 I88, 15.0 +/- 0.1 microM, p < 0.001). Furthermore, isothermal titration calorimetry analyses together with molecular modeling studies showed that CBR1 V88I results in CBR1 isoforms with different binding affinities for the cofactor NADPH (K(d) CBR1 V88, 6.3 +/- 0.6 microM versus K(d) CBR1 I88, 3.8 +/- 0.5 microM). These studies characterize the first functional genetic determinant of CBR1 activity toward relevant physiological and pharmacological substrates.

Effects of haloperidol and its pyridinium metabolite on plasma membrane permeability and fluidity in the rat brain

The use of antipsychotic drugs is limited by their tendency to produce extrapyramidal movement disorders such as tardive dyskinesia and parkinsonism. In previous reports it was speculated that extrapyramidal side effects associated with the butyrophenone neuroleptic agent haloperidol (HP) could be caused in part by the neurotoxic effect of its pyridinium metabolite (HPP(+)). Although both HPP(+) and HP have been shown to induce neurotoxic effects such as loss of cell membrane integrity, no information exists about the difference in the neurotoxic potency, especially in the potency to induce plasma membrane damage, between these two agents. In the present study, we compared the potency of the interaction of HPP(+) and HP with the plasma membrane integrity in the rat brain. Membrane permeabilization (assessed as [(18)F]2-fluoro-2-deoxy-d-glucose-6-phosphate release from brain slices) and fluidization (assessed as the reduction in the plasma membrane anisotropy of 1,6-diphenyl 1,3,5-hexatriene) were induced by HPP(+) loading (at >or=100 microM and >or=10 microM, respectively), while comparable changes were induced only at a higher concentration of HP (=1 mM). These results suggest that HPP(+) has a higher potency to induce plasma membrane damage than HP, and these actions of HPP(+) may partly underlie the pathogenesis of HP-induced extrapyramidal side effects.

Long circulating lipid nanocapsules for drug detoxification

Uncoated and poly(ethylene glycol) (PEG)-decorated lipid nanocapsules (NC) prepared from medium chain triglycerides were investigated both in vitro and in vivo as parenteral detoxifying colloids for their ability to sequester haloperidol, docetaxel and paclitaxel. In vitro studies showed that the uptake depended on the nature of the drug and the composition of NC core and shell. In the case of haloperidol, maximal affinity was achieved upon incorporation of a complexing fatty acid. In plasma lipoprotein distribution studies, the association of both haloperidol and docetaxel into triglyceride-rich lipoprotein fraction was significantly increased in the presence of NC. The ability of the NC to lower the free drug concentrations in incubation medium was confirmed by cytotoxicity studies, where the antiproliferative activity of docetaxel was significantly decreased in the presence of NC. Using docetaxel as drug model, the NC were finally evaluated for their uptake potential in mice by one of the following administration sequences between the drug solution (Taxotere, DTX) and NC: NC-DTX, PEG(NC)-DTX and DTX-PEG(NC). Irrespective of the administration sequence, the NC increased the blood levels of docetaxel due to the in situ sequestration of drug by the circulating carrier. These findings suggest that lipid NC could be used as a non-specific mode to deal with the sequestration of molecules with high affinity for oils.

Venlafaxine extended release (XR) in the treatment of panic disorder

Panic disorder is a chronic, recurrent illness, with a lifetime prevalence of about 5%. It is associated with substantial functional impairment, and studies suggest that treatment with medication alone (and no instruction in exposure to feared and avoided situations) is less than optimal. In fact, 40%-90% of patients in long-term follow-up studies in the late 1980s and early 1990s, treated with antidepressants or high potency benzodiazepines alone, remained somewhat symptomatic. Venlafaxine extended release (XR) was effective and well tolerated in both the short-term and long-term treatment of panic disorder. In 12-week trials, venlafaxine XR was significantly more effective than placebo in achieving a panic-free state (54%-70% vs 34%-48%, p Collapse

Key Words

• venlafaxine xr
• panic disorder
• anxiety disorders
• quality of life

Collapse

MESH Headings Collapse

Grants Collapse

Affiliation(s)

Kevin Kjernisted University of British Columbia Vancouver, British Columbia, Canada
Diane McIntosh

Collapse

Venlafaxine in the treatment of panic disorder

Venlafaxine XR is a novel, dual acting SNRI antidepressant, which inhibits both serotonin and norepinephrine reuptake. Controlled trials have demonstrated the efficacy and safety of venlafaxine in the treatment of panic disorder. Generally well tolerated, with side-effects that usually abate with continued treatment, venlafaxine is an important option to the SSRIs for the treatment of patients with panic disorder.

The pharmacological importance of cytochrome CYP3A4 in the palliation of symptoms: review and recommendations for avoiding adverse drug interactions

BACKGROUND

Adverse drug interactions are major causes of morbidity, hospitalizations, and mortality. The greatest risk of drug interactions occurs through in the cytochrome system. CYP3A4, the most prevalent cytochrome, accounts for 30-50% of drugs metabolized through type I enzymes.

MATERIALS AND METHODS

Palliative patients received medications for symptoms and co-morbidities, many of which are substrate, inhibitors, or promoters of CYP3A4 activity and expression. A literature review on CYP3A4 was performed pertinent to palliative medicine.

DISCUSSION

In this state of the art review, we discuss the CYP3A4 genetics, and kinetics and common medications, which are substrates or inhibitor/promoters of CYP3A4.

CONCLUSION

We made some recommendations for drug choices to avoid clinically important drug interaction.

Pharmacogenetics, drug-metabolizing enzymes, and clinical practice

The application of pharmacogenetics holds great promise for individualized therapy. However, it has little clinical reality at present, despite many claims. The main problem is that the evidence base supporting genetic testing before therapy is weak. The pharmacology of the drugs subject to inherited variability in metabolism is often complex. Few have simple or single pathways of elimination. Some have active metabolites or enantiomers with different activities and pathways of elimination. Drug dosing is likely to be influenced only if the aggregate molar activity of all active moieties at the site of action is predictably affected by genotype or phenotype. Variation in drug concentration must be significant enough to provide "signal" over and above normal variation, and there must be a genuine concentration-effect relationship. The therapeutic index of the drug will also influence test utility. After considering all of these factors, the benefits of prospective testing need to be weighed against the costs and against other endpoints of effect. It is not surprising that few drugs satisfy these requirements. Drugs (and enzymes) for which there is a reasonable evidence base supporting genotyping or phenotyping include suxamethonium/mivacurium (butyrylcholinesterase), and azathioprine/6-mercaptopurine (thiopurine methyltransferase). Drugs for which there is a potential case for prospective testing include warfarin (CYP2C9), perhexiline (CYP2D6), and perhaps the proton pump inhibitors (CYP2C19). No other drugs have an evidence base that is sufficient to justify prospective testing at present, although some warrant further evaluation. In this review we summarize the current evidence base for pharmacogenetics in relation to drug-metabolizing enzymes.

Correlation of haloperidol levels between submandibular saliva and brain in the rat

OBJECTIVE

The clinical usefulness of therapeutic drug monitoring (TDM) for haloperidol using blood samples has to be validated. Despite the potential advantage of TDM using saliva, there are few reports comparing drug levels in saliva and blood. Additionally, the relation between haloperidol levels in saliva and brain, the target organ of this drug, has not been reported. We compared haloperidol levels in rat submandibular saliva, plasma and brain.

DESIGN

Haloperidol was administered through the femoral vein (0.25 mg/kg). Submandibular saliva was collected 30 min after drug administration. To stimulate secretion, the chorda (parasympathetic) and superior cervical ganglion (sympathetic) were electrically stimulated, and pilocarpine was administered. The concentration of haloperidol in saliva, plasma and brain homogenate was determined.

RESULTS

Haloperidol levels in saliva elicited by any stimuli significantly correlated with levels in the brain and plasma. The correlation of haloperidol between saliva and brain was higher than that between plasma and brain. Immunohistochemistry showed that haloperidol was secreted from striated duct cells within the submandibular gland.

CONCLUSION

These results suggested that haloperidol was specifically secreted from the striated duct system, and that salivary drug levels reflect the levels in the brain more precisely than plasma.

Use of psychotropic drugs in patients with epilepsy: interactions and seizure risk

It is now accepted that patients with epilepsy are more prone than the general population to develop psychiatric disorders, being significantly at risk due to psychosocial reasons, the presence of electrophysiologic and anatomopathologic abnormalities mainly in the limbic system, and because they are taking antiepileptic drugs which may have negative psychotropic effects. It is also known that many patients with epilepsy sometimes receive psychotropic medications on account of their psychiatric symptoms. This review focuses on the main problems that a clinician may encompass when treating psychiatric disorders in patients with epilepsy. On one hand, the effects of antiepileptic drugs on mood and behavior for a correct differential diagnosis of psychiatric symptoms. On the other hand, the main factors that may affect choice of therapy, patients' response and compliance, when prescribing antidepressants or antipsychotic drugs, drug interactions and the potential proconvulsive risk are reviewed.

Combined effects of itraconazole and CYP2D6*10 genetic polymorphism on the pharmacokinetics and pharmacodynamics of haloperidol in healthy subjects

This study was to evaluate the combined effects of the CYP3A4 inhibitor itraconazole and the CYP2D6*10 genotype on the pharmacokinetics and pharmacodynamics of haloperidol, a substrate of both CYP2D6 and CYP3A4, in healthy subjects. Nineteen healthy volunteers whose CYP2D6 genotypes were predetermined were enrolled (9 for CYP2D6*1/*1 and 10 for CYP2D6*10/*10). Four subjects (1 for CYP2D6*1/*1 and 3 for CYP2D6*10/*10) did not complete the study because of adverse events. The pharmacokinetics of haloperidol and its pharmacodynamic effects measured for QTc prolongation and neurologic side effects were evaluated after a single dose of 5 mg haloperidol following a pretreatment of placebo or itraconazole at 200 mg/d for 10 days in a randomized crossover manner. Itraconazole pretreatment increased the mean area under the time-concentration curves (AUCs) of haloperidol by 55% compared to placebo pretreatment (21.7 +/- 11.3 vs 33.5 +/- 29.3 ng h/mL). The subjects with CYP2D6*10/*10 genotype showed 81% higher AUC compared to that of subjects with CYP2D6*1/*1 genotype (27.6 +/- 22.2 vs 50.2 +/- 47.1 ng h/mL). In the presence of itraconazole, subjects with CYP2D6*10/*10 showed 3-fold higher AUC of haloperidol compared to that of placebo pretreated subjects with CYP2D6*1/*1 genotype (21.7 +/- 11.3 vs 66.7 +/- 62.1 ng h/mL; P < 0.05). The CYP2D6*10 genotype and itraconazole pretreatment decreased the oral clearance of haloperidol by 24% and 25%, respectively, but without a statistical significance. In the subjects with both CYP2D6*10 genotype and itraconazole pretreatment, however, the oral clearance was significantly decreased to 42% of subjects with wild genotype in the placebo pretreatment (4.7 +/- 3.6 vs 2.0 +/- 1.9 L/h/kg; P < 0.05). Barnes Akathisia Rating Scale (BARS) of subjects with CYP2D6*10/*10 in the presence of itraconazole pretreatment was significantly higher than that of subjects with CYP2D6*1/*1 genotype in the period of placebo pretreatment. Except for this, all other pharmacodynamic estimations did not reach to statistical significance although each CYP2D6*10 genotype and itraconazole pretreatment caused higher value of UKU side effect and BARS scores. The moderate effect of CYP2D6*10 genotype on the pharmacokinetics and pharmacodynamics of haloperidol seems to be augmented by the presence of itraconazole pretreatment.

Prolonged extra-pyramidal side effects after discontinuation of haloperidol as an antiemetic

We describe a case of prolonged extra-pyramidal side effects after discontinuation of haloperidol as an antiemetic.