Therapeutic monitoring of psychotropic drugs: an outline of the AGNP-TDM expert group consensus guideline

Automated Interlaboratory Comparison of Therapeutic Drug Monitoring Data and Its Use for Evaluation of Published Therapeutic Reference Ranges

Therapeutic drug monitoring is a tool for optimising the pharmacological treatment of diseases where the therapeutic effect is difficult to measure or monitor. Therapeutic reference ranges and dose-effect relation are the main requirements for this drug titration tool. Defining and updating therapeutic reference ranges are difficult, and there is no standardised method for the calculation and clinical qualification of these. The study presents a basic model for validating and selecting routine laboratory data. The programmed algorithm was applied on data sets of antidepressants and antipsychotics from three public hospitals in Denmark. Therapeutic analytical ranges were compared with the published therapeutic reference ranges by the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) and in additional literature. For most of the drugs, the calculated therapeutic analytical ranges showed good concordance between the laboratories and to published therapeutic reference ranges. The exceptions were flupentixol, haloperidol, paroxetine, perphenazine, and venlafaxine + o-desmethyl-venlafaxine (total plasma concentration), where the range was considerably higher for the laboratory data, while the calculated range of desipramine, sertraline, ziprasidone, and zuclopenthixol was considerably lower. In most cases, we identified additional literature supporting our data, highlighting the need of a critical re-examination of current therapeutic reference ranges in Denmark. An automated approach can aid in the evaluation of current and future therapeutic reference ranges by providing additional information based on big data from multiple laboratories.

Switching Between LC-ESI-MS/MS and EMIT Methods for Routine TDM of Valproic Acid in Pediatric Patients With Epilepsy: What Clinicians and Researchers Need to Know

Background: Valproic acid (VPA) is a widely used antiseizure medication and its dosing needs to be tailored individually through therapeutic drug monitoring (TDM) to avoid or prevent toxicity. Currently, immune-enzymatic assays such as Enzyme Multiplied Immunoassay Technique (EMIT), and Liquid Chromatography (LC)-based techniques, particularly coupled to Electrospray Ionization Tandem Mass Spectrometry (LC-ESI-MS/MS), resulting a potential lack of concordance between laboratories. Methods: In this study, plasma VPA concentrations were determined for 711 pediatric patients with epilepsy by a routine EMIT assay and by a validated in-house LC-ESI-MS/MS method on the same group of samples, aimed to address the aforementioned concern. Consistency between two assays was evaluated using linear regression and Bland-Altman analysis. Results: The calibration curve was linear in the range of 5.00-300 μg/ml for LC-ESI-MS/MS method and 1.00-150 μg/ml for EMIT assay, respectively. The two methods were proven to be accurate with quality control samples. As a result, a significant correlation between two methods was obtained with a regression equation described as [ EMIT ] = 1.214 × [ LC - ESI - MS / MS ] + 3.054 (r ² = 0.9281). Bland-Altman plot showed a mean bias of 14.5 μg/ml (95% confidence interval (CI) (-0.2, 29.2) and a mean increase of 27.8% (95% CI (3.3, 52.4) measured by EMIT assay more than that measured by LC-ESI-MS/MS method. Conclusion: In conclusion, two methods were closely correlated, but EMIT assay overestimate VPA levels in human plasma compared with LC-ESI-MS/MS method. Due to the observed significant discordance between the tested methods, switching from immunoassays to LC-based techniques for TDM of VPA deserves close attention and therapeutic range of 35.0-75.0 μg/ml may be feasible. However, further studies are needed to evaluate the eligibility of this alternative range in the clinical practice. Clinicians should be informed when switching the VPA quantitation methods during the clinical practice.

Age Impacts Olanzapine Exposure Differently During Use of Oral Versus Long-Acting Injectable Formulations: An Observational Study Including 8,288 Patients

PURPOSE

Olanzapine is a commonly prescribed antipsychotic available as oral and long-acting injectable (LAI) formulations. Data are lacking on the use and safety of olanzapine-LAI in older patients. The aim of this study was to investigate the effect of increasing age on olanzapine exposure during oral versus LAI administration in a real-life setting.

METHODS

This observational study was based on routine therapeutic drug monitoring data collected during 2005-2017. As a measure of exposure, absolute concentrations and concentration/dose ratios of olanzapine were defined as outcome variables. Linear mixed-model analyzes were used to allow for inclusion of multiple samples per patient and adjustment for covariate effects.

RESULTS

Olanzapine concentrations and doses from 8,288 patients (21,378 measurements) were included. The number of patients on oral treatment was 7,893 (42%, 50 years or older), while 395 were using olanzapine-LAI (27%, 50 years or older). In contrast to oral use, where the dose-adjusted concentration of olanzapine increased significantly for patients 50 years or older (P < 0.001), increasing age had no effect on olanzapine concentration following LAI administration (P = 0.550). The effects of smoking habits and gender were equal in oral and olanzapine-LAI users.

CONCLUSION

While the dose-adjusted systemic exposure of olanzapine increases by age after oral administration, these novel findings from a large patient population show that systemic exposure of olanzapine-LAI is unaffected by age, probably due to the lacking influence of age-related changes in gastrointestinal absorption and/or presystemic metabolism. From a pharmacokinetic point of view, it is therefore no reason to restrict the use of olanzapine-LAI in older patients requiring long-term treatment.

Dried Blood Spots Combined With Ultra-High-Performance Liquid Chromatography-Mass Spectrometry for the Quantification of the Antipsychotics Risperidone, Aripiprazole, Pipamperone, and Their Major Metabolites

BACKGROUND

Risperidone, aripiprazole, and pipamperone are antipsychotic drugs frequently prescribed for the treatment of comorbid behavioral problems in children with autism spectrum disorders. Therapeutic drug monitoring (TDM) could be useful to decrease side effects and to improve patient outcome. Dried blood spot (DBS) sample collection seems to be an attractive technique to develop TDM of these drugs in a pediatric population. The aim of this work was to develop and validate a DBS assay suitable for TDM and home sampling.

METHODS

Risperidone, 9-OH risperidone, aripiprazole, dehydroaripiprazole, and pipamperone were extracted from DBS and analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry using a C18 reversed-phase column with a mobile phase consisting of ammonium acetate/formic acid in water or methanol. The suitability of DBS for TDM was assessed by studying the influence of specific parameters: extraction solution, EDTA carryover, hematocrit, punching location, spot volume, and hemolysis. The assay was validated with respect to conventional guidelines for bioanalytical methods.

RESULTS

The method was linear, specific without any critical matrix effect, and with a mean recovery around 90%. Accuracy and imprecision were within the acceptance criteria in samples with hematocrit values from 30% to 45%. EDTA or hemolysis did not skew the results, and no punching carryover was observed. No significant influence of the spot volume or the punch location was observed. The antipsychotics were all stable in DBS stored 10 days at room temperature and 1 month at 4 or -80°C. The method was successfully applied to quantify the 3 antipsychotics and their metabolites in patient samples.

CONCLUSIONS

A UHPLC-MS/MS method has been successfully validated for the simultaneous quantification of risperidone, 9-OH risperidone, aripiprazole, dehydroaripiprazole, and pipamperone in DBS. The assay provided good analytical performances for TDM and clinical research applications.

Inflammation and depression: a causal or coincidental link to the pathophysiology?

This review summarises the evidence that chronic low grade inflammation triggers changes that contribute to the mental and physical ill health of patients with major depression. Inflammation, and the activation of the hypothalamic pituitary axis by stress, are normal components of the stress response but when stress is prolonged and the endocrine and immune system become chronic resulting in the activation of the peripheral macrophages, the central microglia and hypercortisolemia, the neuronal networks are damaged and become dysfunctional. The proinflammatory cytokines, in addition to activating the hypothalamic-pituitary-adrenal axis and thereby increasing cortisol synthesis, also activate the tryptophan-kynurenine pathway. This results in the synthesis of the neurotoxic N-methyl-d-aspartate (NMDA) glutamate agonist quinolinic acid and 3-hydroxykynurenine thereby enhancing oxidative stress and contributes to neurodegeneration which characterise major depression particularly in late life.While antidepressants attenuate some of the endocrine and immune changes caused by inflammation, not all therapeutically effective antidepressants do so. This suggests that drugs which specifically target the immune, endocrine and neurotransmitter systems may be more effective antidepressants.The preliminary clinical evidence that some non-steroidal anti-inflammatory drugs, such as the cyclooxygenase 2 inhibitor celecoxib, can enhance the response to standard antidepressant treatment is therefore considered and a critical assessment made of the possible limitations of such an approach to novel antidepressant development.

Comparison of Capillary and Venous Drug Concentrations After Administration of a Single Dose of Risperidone, Paliperidone, Quetiapine, Olanzapine, or Aripiprazole

Risperidone, paliperidone, quetiapine, olanzapine, and aripiprazole are antipsychotic drugs approved for treating various psychiatric disorders, including schizophrenia. The objective of this randomized, parallel‐group, open‐label study was to compare finger‐stick‐based capillary with corresponding venous whole‐blood and plasma concentrations for these drugs after administration of a single dose to healthy volunteers. All whole‐blood and plasma drug concentrations were measured with validated liquid chromatography–tandem mass spectrometry methods. Capillary and venous concentrations (both in plasma and whole blood) were in close agreement, although a time‐dependent difference was observed, most obviously for olanzapine and paliperidone, with slightly higher capillary versus venous drug concentrations during the first hours after administering a single dose. The observed difference between capillary and venous plasma drug concentrations is expected not to be relevant in clinical practice, considering the wide window of therapeutic concentrations and the wide range of drug concentrations in the patient population for a given dose. Based on these results, finger‐stick‐based capillary drug concentrations have been shown to approximate venous drug concentrations.

Determination of blood concentration levels of psychotropic medications in Rwandan patients

OBJECTIVES

In Rwanda, no therapeutic monitoring of psychotropic drugs is done. This results in difficult treatment optimisation and exposition to a high risk of toxicity and drug ineffectiveness for patients under treatment. This study aimed to determine blood concentration levels of psychotropic drugs in Rwandan patients and identify problems associated with the lack of therapeutic drug monitoring (TDM) of these drugs.

METHODS

The analysis was performed on 1 ml of serum sample using prazepam as internal standard. Regarding the step of sample preparation, we used a liquid-liquid extraction with a mixture of organic solvents: diethyl ether/dichloromethane/hexane/n-amyl alcohol (50/30/20/0.5:V/V). A Waters Alliance 2695 was used for analysis. The chromatography was run on a Symmetry C8 column and as mobile phase acetonitrile and phosphate buffer (pH 3.8) were used.

RESULTS

Concerning the results, serum samples from 128 patients were analysed. Twenty-one different psychotropic drugs belonging to various pharmacological classes were detected and quantified. Analytical results were put into three categories based upon therapeutic reference ranges (TRR) of various drugs: subtherapeutic, therapeutic and supratherapeutic. For a total of 237 analyses, results within TRR represented 46% while 47 and 8% of results were, respectively, below and above TRR.

CONCLUSION

It was therefore concluded that patients under psychotropic treatment in Rwanda are exposed to both the risk of drug ineffectiveness and the risk of toxicity (54%) with only 46% of results within the TRR. Consequently, TDM is needed to optimise psychotropic treatment in Rwandan patients.

Quantitation of the impact of CYP3A5 A6986G polymorphism on quetiapine pharmacokinetics by simulation of target attainment

The aim of this study was to evaluate whether genetic polymorphisms in CYP3A5 and ABCB1 are responsible for the interindividual variability observed in quetiapine pharmacokinetics. Pharmacokinetic data from a randomized crossover study evaluating 2 quetiapine 25 mg immediate-release tablets after single oral dose were used to develop a population pharmacokinetic model. The single nucleotide polymorphisms (SNPs) evaluated for the genotype effects of quetiapine pharmacokinetics were CYP3A5 A6986G and ABCB1 C3435T, along with other demographic variables and formulations. A one-compartment distribution model with linear elimination plus four transit compartments for the delayed absorption adequately described quetiapine disposition. CYP3A5 *1/*1 individuals (n = 3) had 29% increased clearance compared to *1/*3 and *3/*3 individuals. The impact of an increased clearance was evaluated by simulations. By computing the probability of target attainment (PTA) of steady-state therapeutic goal at 1-hour and 12-hour time points after 50-400 mg twice-daily regimens, the results indicated that CYP3A5 genotype has minimal impact on the PTA of the 1-hour concentrations but a significant impact on the 12-hour concentrations. The interpretation based on the simulations does not call for a genotype-based dosing scheme and is consistent with consensus guidelines for quetiapine that therapeutic drug monitoring is considered useful. Clinical Pharmacology in Drug Development.

Safety and pharmacokinetics of atypical antipsychotics in children and adolescents

Pediatric behavioral and affective disorders often require antipsychotic therapy, in combination with psychotherapeutic interventions, for their treatment and stabilization. Although pharmacotherapy can include either typical or atypical antipsychotics, the latter are generally preferred because of their apparently lower risk of adverse effects. Recent controlled trials have demonstrated the efficacy of some of these agents (including aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, ziprasidone) in adolescent schizophrenia and children or adolescent bipolar mania, or to treat severe aggression and self-injury in the context of autism in children and adolescents. Although few studies have systematically monitored their short- and, more importantly, long-term safety, current evidence indicates that sedation, hyperprolactinemia, and metabolic abnormalities such as excess weight gain, diabetes, and related cardiovascular effects were clinically relevant adverse effects in young patients, with the individual agents differing in their propensity to induce these effects. When prescribing antipsychotics for children and adolescents, physicians should therefore be aware of the specific adverse effect profiles and patients should be closely monitored for the short- and long-term development of adverse events. In pediatric patients, the starting dose, titration plan, and maintenance dose of antipsychotics must be based on their pharmacokinetics and metabolism, as in adults. Because there are significant individual differences in drug and active metabolite(s) pharmacokinetics and metabolism, which may be further affected by a number of confounding factors (including demographic variables, phenotype and drug interactions), therapeutic drug monitoring may be a valid tool for individualizing dosage, but its interpretation should also take account of changes in pharmacodynamic sensitivity with the development during childhood and adolescence.

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.

An introduction to drug testing: the expanding role of mass spectrometry

Measurement of drugs and their metabolites in biological fluids is the foundation of both therapeutic drug monitoring (TDM) and toxicology. Though different in their application, each discipline depends upon accurate identification and quantification if the measurements are to be useful. Thousands of methods are described for drug analysis but until recently most have relied upon analytical tools, such as spectrophotometry and immunoassay, that suffer from lack of specificity and sensitivity. The introduction of methods based on mass spectrometry (MS), coupled to gas or liquid chromatography, has revolutionized these areas. The methods are proving to be robust, versatile, and economical. This chapter introduces the reader to the application of MS to TDM and toxicology, the steps that should be considered during implementation, and the processes that should be implemented to assure continued quality.

Psychotropic drug-induced weight gain and other metabolic complications in a Swiss psychiatric population

PURPOSE

To describe the weight gain-related side-effects of psychotropic drugs and their consequences on metabolic complications (hypercholesterolemia, obesity) in a Swiss cohort of psychiatric patients.

METHOD

This cross-sectional observational study was performed in an out-patient psychiatric division with patients having received for more than 3 months the following drugs: clozapine, olanzapine, quetiapine, risperidone, lithium, and/or valproate. Clinical measures and lifestyle information (smoking behaviour, physical activity) were recorded.

RESULTS

196 inclusions were completed. Weight gain (≥10% of initial weight) following drug treatment was reported in 47% of these patients. Prevalence of obesity (BMI ≥ 30), hypercholesterolemia (≥6.2 mmol/L) and low HDL-cholesterol (<1.0 mmol/L in men, <1.3 mmol/L in women) were present in 38%, 21%, and 27% of patients, respectively. A higher standardised dose, an increase of appetite following medication introduction, the type of medication (clozapine or olanzapine > quetiapine or risperidone > lithium or valproate), and the gender were shown to be significantly associated with evolution of BMI.

CONCLUSION

High prevalence of obesity and hypercholesterolemia was found in an out-patient psychiatric population and confirms drug-induced weight gain complications during long-term treatment. The results support the recently published recommendations of monitoring of metabolic side-effects during treatment with atypical antipsychotics. Moreover, the weight gain predictors found in the present study could help to highlight patients with special health care management requirement.

Medication adherence in outpatients with severe mental disorders: relation between self-reports and serum level

Medication nonadherence in severe mental disorders is an important clinical issue, but estimates vary between studies. There is a need for valid self-reports for both research and clinical practice. This study examined the level of adherence to prescribed medication in outpatients with severe mental disorders and evaluated the validity of a simple self-report rating of adherence. From an ongoing study of severe mental disorders, 280 patients with schizophrenia and bipolar disorder who were prescribed psychopharmacological agents were included. We assessed adherence with serum concentration of medicines and tested the sensitivity and specificity of a simple self-report questionnaire for patients and compared with a report from health personnel. Adherence rate defined by serum concentrations within reference level was 61.6% in the total sample, 58.4% for schizophrenia and 66.3% for bipolar disorder. The patients' self-report scores overestimated adherence, but correlated significantly to health personnel scores (r = 0.50) and to serum concentration of medication (r = 0.52); the positive predictive value was 70%, and the negative predictive value was 91%. In this naturalistic sample, outpatients with severe mental disorders showed relatively good adherence to prescribed medication, and self-report questionnaires seem to be a valid method for measuring adherence.

Serum concentrations of antidepressant drugs in a naturalistic setting: compilation based on a large therapeutic drug monitoring database

A compilation of therapeutic drug monitoring data for 15 antidepressant drugs in a naturalistic routine clinical setting is presented. A substantial number of serum concentrations, at different daily doses, are outlined, and the intraindividual and overall serum concentration coefficient of variation for a respective substance is presented. Also, concentration comparisons between women and men, and patients older or younger than 65 years are made. The drugs included are amitriptyline (n = 394), citalopram (n = 5457), clomipramine (n = 400), escitalopram (n = 3066), fluoxetine (n = 793), fluvoxamine (n = 165), mianserin (n = 1063), mirtazapine (n = 1427), moclobemide (n = 200), nortriptyline (n = 206), paroxetine (n = 1677), reboxetine (n = 85), sertraline (n = 2998), trimipramine (n = 158), and venlafaxine (n = 1781). Of the 9 drugs exhibiting linear (first order) kinetics, all but reboxetine gave a significant negative dose-to-dose-normalized correlation with concentrations, that is an increased clearance with higher dose. When dose was correlated to the metabolite:parent substance ratio for drugs exhibiting linear kinetics, citalopram and mianserin gave a positive slope, contrary to a negative slope shown for sertraline and venlafaxine. The intraindividual variations of the serum concentrations were lower than the overall variations, and the intraindividual variation of the metabolite:parent substance ratio was lower than the intraindividual variation of respective parent substance (except clomipramine and mianserin). Women had significantly higher serum concentrations than men (significant for citalopram, escitalopram, mianserin, mirtazapine, and venlafaxine), and patients older than 65 years had higher serum concentrations than the younger ones for all drugs except amitriptyline, moclobemide, and trimipramine. By presenting a comprehensive compilation of therapeutic drug monitoring data for each drug, a reference tool is created, in addition to improved pharmacokinetic knowledge of antidepressant drugs.

Pharmacokinetics of olanzapine in Chinese male schizophrenic patients with various smoking behaviors

Tobacco consumption has been recognized as a factor mediating the interindividual variations in olanzapine's pharmacokinetics and pharmacodynamics. The primary objective of this study was to describe the dose effect of smoking on the dose-plasma concentration relationship and the pharmacokinetics of oral olanzapine in male schizophrenic patients using high-performance liquid chromatography coupled with electrochemical detector. Twenty-seven male schizophrenic inpatients were recruited and were stratified into the following groups according to smoking behaviors: non-smokers (n=9), light-smokers (1-4 cigarettes per day; n=9), and heavy-smokers (>or=5 cigarettes per day; n=9). Plasma olanzapine concentrations were determined up to 120 h following a single oral dose of 10 mg olanzapine. The pharmacokinetic parameters were calculated by the non-compartment method using WinNonlin software. Results show that there was a significant correlation among non-smokers (n=9; 0.79; p=0.01) or combined with light-smokers (n=18; 0.62; p<0.01) between peak plasma olanzapine concentrations (Cmax) and their individual dose-corrected by body weight, but this correlation did not appear in heavy-smokers. There were no significant differences between non-smokers and light-smokers except for significant decreased AUC0-->120 by 45.1% in light-smokers. The mean C(max) and the mean area under the plasma concentration-time curve from time zero to 120 h (AUC0-->120) of the heavy-smoking patients was 9.3+/-4.3 ng/ml (65.2% reduction compared to the non-smokers) and 302.4+/-167.8 h ng/ml (67.6% reduction compared to the non-smokers), respectively. In summary, a daily consumption of 5 cigarettes is probably sufficient for induction of olanzapine metabolism. Smoking cessation is recommended for olanzapine therapy to have better prediction for therapeutic dosages particularly in heavy-smokers. Compared to non-smokers, heavy-smokers therefore require a 50-100% increase in olanzapine doses. Therapeutic drug monitoring will need to be considered when schizophrenic patients change their smoking behaviors.

Pharmacological validation of a chronic social stress model of depression in rats: effects of reboxetine, haloperidol and diazepam

Chronic social stress is one of the most important factors responsible for precipitation of depressive disorder in humans. In recent years, the impact of social stress on the development of psychopathologies has been thoroughly investigated in preclinical animal studies. We have shown recently that behavioural effects of chronic social stress in rats can be reversed by citalopram and fluoxetine. This study has been designed for further pharmacological validation of the chronic social stress paradigm as a model of depressive symptoms in rats. For this, rats were subjected to 5 weeks of daily social defeat and were in parallel treatment for a clinically relevant period of 4 weeks with the antidepressant drug reboxetine (40 mg/kg/day) and the neuroleptic drug haloperidol (2 mg/kg/day). The anxiolytic diazepam (1 mg/kg) was administered acutely at the end of the stress period. Stress caused decreased locomotor and exploratory behaviours, decreased sucrose preference and increased immobility in the forced swim test, but did not affect behaviour in the elevated plus maze. Four weeks of oral treatment with reboxetine ameliorated the adverse effects of social stress and normalized behaviours related to motivation and reward sensitivity. The treatment with haloperidol worsened the adverse effects of chronic social stress having effects similar to stress on reward and motivation-related behaviours. Diazepam reduced anxiety-related behaviours as measured in elevated plus maze in control animals having no effects on socially stressed individuals. Neither sucrose preference nor performance in forced swim test was affected by diazepam. The effectiveness and selectivity of the treatment with the antidepressant reboxetine in ameliorating socially induced behavioural disturbances supports the validity of the chronic social stress as a model of depressive-like symptoms in rats.

The role of anxiety in the development of levodopa-induced dyskinesias in an animal model of Parkinson's disease, and the effect of chronic treatment with the selective serotonin reuptake inhibitor citalopram

INTRODUCTION

Levodopa-induced dyskinesia (LID) is an inevitable complication of the long-term treatment of Parkinson's disease (PD) with levodopa. In a rat model of LID, we observed that animals of almost identical genetic but slightly different environmental backgrounds displayed a very different profile in terms of their development and severity of LID.

MATERIALS AND METHODS

We hypothesised that this heterogeneity can be attributed to different levels of anxiety in individual animals. We evaluated the basal anxiety level of rats in this study using the elevated plus maze (EPM), open field (OF) test, and plasma corticosterone level. These animals then received unilateral 6-hydroxydopamine lesions of the nigrostriatal pathway after which they were primed to develop LID. Finally, we manipulated the anxiety level of these animals by citalopram treatment over a 9-week period before they were killed.

RESULTS

Although we could not establish an association between the anxiety level of rats with either the onset or severity of LID, our results showed that citalopram was able to mediate a partial alleviation in LID after chronic treatment, and the extent of recovery was negatively correlated to the anxiety measures of individual animals. Furthermore, this citalopram-mediated LID recovery appeared to be independent of any changes in striatal cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) and cyclin-dependent kinase 5 (Cdk5) system, in contrast to our previous studies with fetal ventral mesencephalon transplants. However, chronic citalopram treatment almost completely abolished the expression of serotonin receptor 1B (5HT1B) in the striatum in animals exhibiting LID recovery.

CONCLUSIONS

These results indicate a novel association of serotonin receptors in the development of LID and contributes to the evidence that the serotonergic system may play an important role in such movements.

Effect of chronic citalopram on serotonin-related and stress-regulated genes in the dorsal raphe nucleus of the rat

Using a model of depression in which chronic social stress induces depressive-like symptoms, we investigated effects of the selective serotonin-reuptake inhibitor (SSRI) citalopram on gene expression in the dorsal raphe nucleus of male rats. Expression of tryptophan hydroxylase (TPH) protein was found to be upregulated by the stress and normalized by citalopram, while mRNAs for genes TPH 1 and 2 were differentially affected. Citalopram had no effect on serotonin transporter mRNA but reduced serotonin-1A autoreceptor mRNA in stressed animals. The SSRI prevented the stress-induced upregulation of mRNA for CREB binding protein, synaptic vesicle glycoprotein 2b and the glial N-myc downstream-regulated gene 2, but increased mRNA for neuron-specific enolase (NSE) in both stressed and unstressed animals having no effect on stress-induced upregulation of NSE protein. These findings demonstrate that in the dorsal raphe nucleus of chronically stressed rats, citalopram normalizes TPH expression and blocks stress effects on distinct genes related to neurotransmitter release and neuroplasticity.

Tricyclic antidepressant pharmacology and therapeutic drug interactions updated

New data on the pharmacology of tricyclic antidepressants (TCAs), their affinities for human cloned CNS receptors and their cytochrome P450 enzyme inhibition profiles, allow improved deductions concerning their effects and interactions and indicate which of the TCAs are the most useful. The relative toxicity of TCAs continues to be more precisely defined, as do TCA interactions with selective serotonin reuptake inhibitors (SSRIs). TCA interactions with monoamine oxidase inhibitors (MAOIs) have been, historically, an uncertain and difficult question, but are now well understood, although this is not reflected in the literature. The data indicate that nortriptyline and desipramine have the most pharmacologically desirable characteristics as noradrenaline reuptake inhibitors (NRIs), and as drugs with few interactions that are also safe when coadministered with either MAOIs or SSRIs. Clomipramine is the only available antidepressant drug that has good evidence of clinically relevant serotonin and noradrenaline reuptake inhibition (SNRI). These data assist drug selection for monotherapy and combination therapy and predict reliably how and why pharmacodynamic and pharmacokinetic interactions occur. In comparison, two newer drugs proposed to have SNRI properties, duloxetine and venlafaxine, may have insufficient NRI potency to be effective SNRIs. Combinations such as sertraline and nortriptyline may therefore offer advantages over drugs like venlafaxine that have fixed ratios of SRI/NRI effects that are not ideal. However, no TCA/SSRI combination is sufficiently safe to be universally applicable without expert knowledge. Standard texts (e.g. the British National Formulary) and treatment guidelines would benefit by taking account of these new data and understandings.

Therapeutic monitoring of valproate in psychiatry: how far have we progressed?

Valproate (VPA) is a well-established anticonvulsant drug that has found increasing use as a psychotherapeutic agent. The drug is currently used in the management of bipolar, depressive, anxiety, and psychotic disorders; alcohol withdrawal and dependence; agitation associated with dementia; and borderline personality disorder. Despite such widespread use, studies focusing on the concentration-response relationship of VPA in psychiatry are limited. This article examines the rationale for therapeutic monitoring of VPA in psychiatric disorders and reviews reports of VPA concentrations measured during efficacy studies of this drug in psychiatry. Most studies have been open-labeled and uncontrolled, and have not placed the determination of a target concentration range as a primary objective. Furthermore, most studies have used the therapeutic range (50-100 mg/L) for seizure disorders to guide dosage in the psychiatric disorders, although study outcomes have suggested the need to redefine a threshold concentration in the different psychiatric conditions. With the increasing popularity of VPA as a psychotropic agent, it is clear that further investigation of the plasma concentration range associated with efficacy in psychiatric conditions is warranted.

Pharmacokinetic Variability of Aripiprazole and the Active Metabolite Dehydroaripiprazole in Psychiatric Patients

Aripiprazole is a new atypical antipsychotic drug with a partial agonist activity at dopamine 2 and serotonin 1A receptors. The metabolism of aripiprazole involves both cytochrome P450 2D6 (CYP2D6) and CYP3A4. This study investigated the pharmacokinetic variability of aripiprazole and the active metabolite dehydroaripiprazole on the basis of 155 drug monitoring samples from psychiatric patients treated with therapeutic doses of aripiprazole (10-30 mg/day). Serum concentrations of drug and metabolite were determined by liquid chromatographic and tandem mass spectrometric detection. Pharmacokinetic variability was expressed as the range in concentration/dose (C/D) ratios, and the effect of sex and occasionally coprescribed CYP2D6 or CYP3A4 inhibitors/inducers was studied. In addition, the dose-concentration relationship and combined interquartile range of concentrations obtained at low dose (10-15 mg/day) and high dose (20-30 mg/day) were described. Individual C/D ratios ranged 37-fold for aripiprazole, 78-fold for dehydroaripiprazole, and 27-fold for the active sum of aripiprazole + dehydroaripiprazole. Median C/D ratios in male and female patients differed by less than 15%, and none of the differences were significant (P > 0.14). Cases of concurrent CYP3A4 inducers/inhibitors were not found, but three patients were coprescribed the potent CYP2D6 inhibitors paroxetine or fluoxetine. No consistent difference in C/D ratio was observed in these three patients compared with the rest of the patients. There was a proportional dose-concentration relationship in the population, and the combined interquartile ranges were 230 to 960 nmol/L for aripiprazole and 330 to 1210 nmol/L for aripiprazole + dehydroaripiprazole. In conclusion, pharmacokinetic variability of aripiprazole is extensive in psychiatric patients but apparently not dependent on dose or sex. The variability of the pharmacologic active sum of aripiprazole + dehydroaripiprazole is 25% to 30% less than aripiprazole, suggesting that variability of aripiprazole is partly determined by metabolism to dehydroaripiprazole.

The effect of variable cigarette consumption on the interaction with clozapine and olanzapine

OBJECTIVE

Cigarette smoking has been shown in several studies to induce the metabolism of the cytochrome P4501A2 (CYP1A2) substrates clozapine and olanzapine. The aim of the present study was to investigate the dose-dependent effect of cigarette smoking on serum concentrations of these drugs in a naturalistic setting.

METHODS

In 73 schizophrenic patients recruited from psychiatric nursing homes, patient characteristics, smoking habits, drug dosing and serum concentrations of clozapine (n=33) and olanzapine (n=40) were registered. Concentration to dose (C/D) ratios of clozapine and olanzapine in non-smokers and subgroups of smokers were compared.

RESULTS

Fifty-nine patients (80%) were smokers and these were stratified into the following groups according to smoking habits: 1-6 (n=0), 7-12 (n=13), 13-19 (n=18) and >or=20 (n=28) cigarettes daily. While the mean ratio was twice as high in non-smokers compared to smokers for both drugs (p<0.01), the C/D ratios of clozapine and olanzapine were not significantly different between the subgroups of smokers (p >0.15). Absolute serum concentrations were also higher in non-smokers compared to smokers: 50% for clozapine (p=0.058) and 67% for olanzapine (p<0.01).

CONCLUSION

A daily consumption of 7-12 cigarettes is probably sufficient for maximum induction of clozapine and olanzapine metabolism. A 50% lower starting dose of both drugs in non-smokers seems rational to avoid side effects.

Therapeutic Monitoring of Clozapine in Australia: The Need for Consensus

In the absence of well-defined guidelines for the monitoring of plasma concentrations of clozapine, this study examined the practices of seven laboratories from four states in Australia. Laboratories analyzed 5 freeze-dried serum samples containing a mixture of clozapine and norclozapine in varying concentrations and the measurement data were analyzed for accuracy and precision. Additional information on laboratory practices was obtained through questionnaire responses. Measurement precision amongst the laboratories was good but there were significant differences in the accuracy of measurements from one laboratory. There were differences in the ranges for which assays had been validated and in suggested therapeutic ranges. These differences could have a significant impact on the interpretation of measured concentrations and patient care, and emphasize the need for consensus in this area. Repeat concentration measurements are recommended in the case of drug concentration measurements that are inconsistent with clinical observations or previous measurements.

Citalopram counteracts depressive-like symptoms evoked by chronic social stress in rats

Recently, we have described a new model of chronic social stress in rats, based on the resident-intruder paradigm. In this model, rats show behavioural changes that may be considered correlates of depressive symptoms, such as anhedonia and motivational deficits. The present study was designed for pharmacological validation of this model. Animals were socially stressed for 5 weeks and, in parallel, after the first week of stress, they were subjected to chronic (4 weeks) treatment with the antidepressant drug citalopram. The drug was administered via drinking water (30 mg/kg). The optimal dose of citalopram was determined in a pilot study. After 4 weeks of treatment, plasma levels of citalopram and its metabolite were found to be within the human therapeutic range. The effects of social stress and citalopram treatment were assessed by behavioural tests. Chronically stressed rats showed reduced locomotor and exploratory activity, reduced sucrose preference and increased immobility time in the forced swimming test. Chronic oral administration of citalopram abolished those effects and normalized behaviours related to motivation and reward sensitivity. These observations provide evidence for the predictive validity of the chronic social stress paradigm as a model of depressive symptoms in rats.

Assay of Olanzapine in Human Plasma by a Rapid and Sensitive Gas Chromatography-Nitrogen Phosphorus Selective Detection (GC-NPD) Method

A gas chromatography-nitrogen phosphorus selective detection (GC-NPD) method with a simple 1-step sample preparation was developed for the assay of the antipsychotic drug olanzapine in plasma. Within a time of analysis of 7 minutes, an HP-5 fused-silica capillary (25 m x 0.2 mm ID, 0.33-microm film thickness, 0.7 mL N2 as carrier gas) provided selectivity with respect to about 30 psychotropic drugs and the internal standard ethylolanzapine. Calibration was linear between 1 and 50 ng/mL and crossed the origin (LOD = 0.3 ng/mL). Intraday precision was 6.7%, 2.7%, and 1.4% at plasma concentrations of 1, 5, and 50 ng/mL, respectively. Interday precision was 4.6% at 20 ng/mL. Accuracy in commercial interlaboratory tests was 108.7% and 88.5%. The method also provided good accuracy in comparison with an HPLC method for patient samples (slope 1.003, r = 0.953) and spiked samples (slope 0.881, r = 0.998). GC-NPD with a simple sample preparation is regarded as an alternative for the assay of olanzapine plasma concentrations in therapeutic drug monitoring (TDM) and in pharmacokinetic studies. Smokers and patients taking concomitant carbamazepine had reduced plasma concentrations of olanzapine. Women and patients older than 60 years had increased plasma olanzapine concentrations.