Plasma levels of second-generation antipsychotics and clinical response in acute psychosis: a review of the literature

Therapeutic Drug Monitoring in Psychiatry: Enhancing Treatment Precision and Patient Outcomes

Psychiatric disorders often require pharmacological interventions to alleviate symptoms and improve quality of life. However, achieving an optimal therapeutic outcome is challenging due to several factors, including variability in the individual response, inter-individual differences in drug metabolism, and drug interactions in polytherapy. Therapeutic drug monitoring (TDM), by measuring drug concentrations in biological samples, represents a valuable tool to address these challenges, by tailoring medication regimens to each individual. This review analyzes the current landscape of TDM in psychiatric practice, highlighting its significance in optimizing drug dosages, minimizing adverse effects, and improving therapeutic efficacy. The metabolism of psychiatric medications (i.e., mood stabilizers, antipsychotics, antidepressants) often exhibits significant inter-patient variability. TDM can help address this variability by enhancing treatment personalization, facilitating early suboptimal- or toxic-level detection, and allowing for timely interventions to prevent treatment failure or adverse effects. Furthermore, this review briefly discusses technological advancements and analytical methods supporting the implementation of TDM in psychiatric settings. These innovations enable quick and cost-effective drug concentration measurements, fostering the widespread adoption of TDM as a routine practice in psychiatric care. In conclusion, the integration of TDM in psychiatry can improve treatment outcomes by individualizing medication regimens within the so-called precision medicine.

Evidence for Therapeutic Drug Monitoring of Atypical Antipsychotics

Second-generation antipsychotics (SGAs), also known as atypical antipsychotics, are a newer class of antipsychotic drugs used to treat schizophrenia, bipolar disorder, and related psychiatric conditions. The plasma concentration of antipsychotic drugs is a valid measure of the drug at its primary target structure in the brain, and therefore determines the efficacy and safety of these drugs. However, despite the well-known high variability in pharmacokinetics of these substances, psychiatric medication is usually administered in uniform dosage schedules. Therapeutic drug monitoring (TDM), as the specific method that can help personalised medicine in dose adjustment according to the characteristics of the individual patient, minimizing the risk of toxicity, monitoring adherence, and increasing cost-effectiveness in the treatment, thus seems to be an elegant tool to solve this problem. Non-response to therapeutic doses, uncertain adherence to medication, suboptimal tolerability, or pharmacokinetic drug-drug interactions are typical indications for TDM of SGAs. This review aims to summarize an overview of the current knowledge and evidence of the possibilities to tailor the dosage of selected SGAs using TDM, including the necessary pharmacokinetic parameters for personalised pharmacotherapy.

Therapeutic Reference Range for Aripiprazole in Schizophrenia Revised: a Systematic Review and Metaanalysis

RATIONALE

While one of the basic axioms of pharmacology postulates that there is a relationship between the concentration and effects of a drug, the value of measuring blood levels is questioned by many clinicians. This is due to the often-missing validation of therapeutic reference ranges.

OBJECTIVES

Here, we present a prototypical meta-analysis of the relationships between blood levels of aripiprazole, its target engagement in the human brain, and clinical effects and side effects in patients with schizophrenia and related disorders.

METHODS

The relevant literature was systematically searched and reviewed for aripiprazole oral and injectable formulations. Population-based concentration ranges were computed (N = 3,373) and pharmacokinetic influences investigated.

RESULTS

Fifty-three study cohorts met the eligibility criteria. Twenty-nine studies report blood level after oral, 15 after injectable formulations, and nine were positron emission tomography studies. Conflicting evidence for a relationship between concentration, efficacy, and side effects exists (assigned level of evidence low, C; and absent, D). Population-based reference ranges are well in-line with findings from neuroimaging data and individual efficacy studies. We suggest a therapeutic reference range of 120-270 ng/ml and 180-380 ng/ml, respectively, for aripiprazole and its active moiety for the treatment of schizophrenia and related disorders.

CONCLUSIONS

High interindividual variability and the influence of CYP2D6 genotypes gives a special indication for Therapeutic Drug Monitoring of oral and long-acting aripiprazole. A starting dose of 10 mg will in most patients result in effective concentrations in blood and brain. 5 mg will be sufficient for known poor metabolizers.

Concentration-Effect Relationships of Psychoactive Drugs and the Problem to Calculate Therapeutic Reference Ranges

BACKGROUND

Despite the obvious potential of Therapeutic Drug Monitoring (TDM) as a tool to optimize psychopharmacotherapy, especially treatment with mood-stabilizing, antidepressant and antipsychotic drugs, acceptance of TDM as a routine tool is still limited. A serious scientific argument against the regular use of TDM is the lack of evidence for a concentration-dependent clinical effect. The aim of this review was to highlight methodological problems leading to poor or even negative concentration-effect relationships and to show how therapeutically effective concentrations of psychoactive drugs can be determined using routine TDM databases.

METHODS

Reports on concentration-effect relationships of psychoactive drugs were analyzed with regard to applied methods. From routine TDM databases of patients who had been treated with antidepressant or antipsychotic drugs and whose improvement was measured by the clinical global impressions scale, mean and median drug concentrations were calculated and compared with reference ranges recommended by TDM guidelines.

RESULTS

Few fixed-dose studies with adequate design and data analysis demonstrated a correlation between drug concentration and clinical effect for psychoactive drugs. Most studies, however, mostly retrospective analyses of TDM databases, failed to find significant concentration-effect relationships because of flexible dosing. They were not suitable for the determination of therapeutically effective drug concentrations. Using TDM databases of antidepressant and antipsychotic drug concentrations in blood of patients who were categorized as responders by the clinical global impressions score, the interquartile ranges of drug concentrations (25th-75th percent range) can be shown to be very close to the therapeutic reference ranges recommended in guidelines for TDM in psychiatry.

CONCLUSIONS

This review provides a discussion on why simple correlation analyses of psychoactive drug concentrations in blood and clinical effects are obsolete for flexible-dose studies or TDM databases. TDM databases, however, can and should be used to calculate drug concentrations in blood of patients who had responded to the drugs. Interquartile ranges can be regarded and used as preliminary therapeutic reference ranges.

Serum Concentrations of Paliperidone After Administration of the Long-Acting Injectable Formulation

Background:

The pharmacokinetics of long-acting intramuscular paliperidone in a naturalistic setting is not well documented. The objective of this study was to investigate the relationship between dose and serum concentrations of paliperidone using data from a routine therapeutic drug monitoring service.

Methods:

Serum concentration measurements in 310 samples from 110 male and 75 female patients receiving depot injections of paliperidone were retrospectively retrieved from the therapeutic drug monitoring database.

Results:

The median dose was 100 mg every 28 days. The median concentration/dose (C/D) ratio of paliperidone was 16.1 (nmol/L)/(mg/d), with a 10–90 percentile range of 7.8–31.0 (nmol/L)/(mg/d). Dose-adjusted serum concentrations were 33% higher in patients 65 years or older and more than 50% lower in patients taking the p-glycoprotein inducer carbamazepine. There were no significant effects of sex or dose on the C/D ratio. The median serum concentrations of paliperidone at the end of the dose interval were 31 nmol/L at an intramuscular dose of 50 mg/28 d, 53 nmol/L after a dose of 75 mg/28 d, 59 nmol/L after a dose of 100 mg/28 d, and 93 nmol/L after a dose of 150 mg/28 d. Forty-five percent of the measurements were lower than the suggested therapeutic range of 20–60 ng/mL (47–140 nmol/L).

Conclusions:

The data show a 4-fold interindividual difference in dose-adjusted serum concentrations within the 10–90 percentile range and illustrate the significant effects of age and p-glycoprotein induction on the pharmacokinetics of paliperidone. The study also indicates that at least in some patients, it might take longer time than anticipated to reach steady state.

Molecular targets of atypical antipsychotics: From mechanism of action to clinical differences

The introduction of atypical antipsychotics (AAPs) since the discovery of its prototypical drug clozapine has been a revolutionary pharmacological step for treating psychotic patients as these allow a significant recovery not only in terms of hospitalization and reduction in symptoms severity, but also in terms of safety, socialization and better rehabilitation in the society. Regarding the mechanism of action, AAPs are weak D₂ receptor antagonists and they act beyond D₂ antagonism, involving other receptor targets which regulate dopamine and other neurotransmitters. Consequently, AAPs present a significant reduction of deleterious side effects like parkinsonism, hyperprolactinemia, apathy and anhedonia, which are all linked to the strong blockade of D₂ receptors. This review revisits previous and current findings within the class of AAPs and highlights the differences in terms of receptor properties and clinical activities among them. Furthermore, we propose a continuum spectrum of "atypia" that begins with risperidone (the least atypical) to clozapine (the most atypical), while all the other AAPs fall within the extremes of this spectrum. Clozapine is still considered the gold standard in refractory schizophrenia and in psychoses present in Parkinson's disease, though it has been associated with adverse effects like agranulocytosis (0.7%) and weight gain, pushing the scientific community to find new drugs as effective as clozapine, but devoid of its side effects. To achieve this, it is therefore imperative to characterize and compare in depth the very complex molecular profile of AAPs. We also introduce relatively new concepts like biased agonism, receptor dimerization and neurogenesis to identify better the old and new hallmarks of "atypia". Finally, a detailed confrontation of clinical differences among the AAPs is presented, especially in relation to their molecular targets, and new means like therapeutic drug monitoring are also proposed to improve the effectiveness of AAPs in clinical practice.

Safety of antipsychotics for the treatment of schizophrenia: a focus on the adverse effects of clozapine

Clozapine, a dibenzodiazepine developed in 1961, is a multireceptorial atypical antipsychotic approved for the treatment of resistant schizophrenia. Since its introduction, it has remained the drug of choice in treatment-resistant schizophrenia, despite a wide range of adverse effects, as it is a very effective drug in everyday clinical practice. However, clozapine is not considered as a top-of-the-line treatment because it may often be difficult for some patients to tolerate as some adverse effects can be particularly bothersome (i.e. sedation, weight gain, sialorrhea etc.) and it has some other potentially dangerous and life-threatening side effects (i.e. myocarditis, seizures, agranulocytosis or granulocytopenia, gastrointestinal hypomotility etc.). As poor treatment adherence in patients with resistant schizophrenia may increase the risk of a psychotic relapse, which may further lead to impaired social and cognitive functioning, psychiatric hospitalizations and increased treatment costs, clozapine adverse effects are a common reason for discontinuing this medication. Therefore, every effort should be made to monitor and minimize these adverse effects in order to improve their early detection and management. The aim of this paper is to briefly summarize and provide an update on major clozapine adverse effects, especially focusing on those that are severe and potentially life threatening, even if most of the latter are relatively uncommon.

Application of plasma levels of olanzapine and N-desmethyl-olanzapine to monitor metabolic parameters in patients with schizophrenia

Metabolic disturbance is a common side effect of olanzapine (OLZ); however, the relationships between plasma OLZ concentration (C_OLZ) and metabolic disturbance remain unclear. Our previous study revealed that C_OLZ≧22.77ng/mL was a positive predictor of therapeutic efficacy in patients with schizophrenia. This study aimed to investigate the roles of OLZ or N-desmethyl-olanzapine (DMO) in metabolic outcomes among OLZ-treated patients with schizophrenia. The metabolic syndrome (MS) was diagnosed based on the modified the National Cholesterol Education Program Adult Treatment Panel III criteria for Asians. HPLC-ECD analytical system was applied to determine the C_OLZ and DMO concentration (C_DMO). The absolute drug levels and concentration-to-dose ratios (C/D ratios) were tested for their correlations to metabolic parameters. Total 151 fasting blood samples from patients with schizophrenia were collected. DMO C/D ratio negatively correlated with weight, body mass index, waist circumference, and C-peptide level. The receiver operator characteristic analysis determined a threshold C_DMO>5.63ng/mL and DMO C/D ratio>0.35ng/mL/mg were negative predictors of MS. The C_OLZ/C_DMO ratio>6.03 was identified as positive predictor of MS. Combined with previous study result, we proposed that the optimal OLZ treatment should maintain C_OLZ/C_DMO ratio between 3 and 6 to maximize the clinical efficacy and minimize the metabolic side effects. Our findings suggested that therapeutic drug monitoring on OLZ and DMO is a valuable tool to monitor metabolic side effects in OLZ-treated patients with schizophrenia.

Antipsychotic plasma levels in the assessment of poor treatment response in schizophrenia

OBJECTIVE

Treatment resistance is a challenge for the management of schizophrenia. It is not always clear whether inadequate response is secondary to medication ineffectiveness, as opposed to medication underexposure due to non-adherence or pharmacokinetic factors. We investigated the prevalence of subtherapeutic antipsychotic plasma levels in patients identified as treatment-resistant by their treating clinician.

METHOD

Between January 2012 and April 2017, antipsychotic plasma levels were measured in 99 individuals provisionally diagnosed with treatment-resistant schizophrenia by their treating clinicians, but not prescribed clozapine. Patients were followed up to determine whether they were subsequently admitted to hospital.

RESULTS

Thirty-five per cent of plasma levels were subtherapeutic, and of these, 34% were undetectable. Black ethnicity (P = 0.006) and lower dose (P < 0.001) were significantly associated with subtherapeutic/undetectable plasma levels. Individuals with subtherapeutic/undetectable levels were significantly more likely to be admitted to hospital (P = 0.02).

CONCLUSION

A significant proportion of patients considered treatment-resistant have subtherapeutic antipsychotic plasma levels, and this is associated with subsequent admission. The presence of subtherapeutic plasma levels may suggest a need to address adherence or pharmacokinetic factors as opposed to commencing clozapine treatment. While antipsychotic levels are not recommended for the routine adjustment of dosing, they may assist with the assessment of potential treatment resistance in schizophrenia.

Accuracy of Clinician Assessments of Medication Status in the Emergency Setting: A Comparison of Clinician Assessment of Antipsychotic Usage and Plasma Level Determination

PURPOSE

The present study aimed to assess the level of agreement between clinicians' routine assessments of medication status and plasma levels of commonly prescribed antipsychotic medications in patients presenting to an emergency room with an exacerbation of psychosis.

METHODS

We studied 105 patients presenting to an emergency room and admitted to an inpatient psychiatric unit with a diagnosis of schizophrenia, schizoaffective disorder, bipolar I disorder, or psychotic disorder not otherwise specified and a prior outpatient medication regimen including risperidone, olanzapine, quetiapine, aripiprazole, or paliperidone. Plasma levels of antipsychotics were drawn and sent to a specialty laboratory for testing.

FINDINGS

Of the 97 patients with usable samples, 33 (34%) were found to have therapeutic antipsychotic levels. Of these, 22 were judged by emergency room staff to be taking their medications at the appropriately prescribed doses, whereas 11 were judged not to be taking medication at all. Sixty-four patients were found to have subtherapeutic antipsychotic levels, 31 of whom had been assessed to be taking medication as prescribed. Emergency assessment of medication status predicted therapeutic and nontherapeutic antipsychotic levels at rates of 41.5% and 75%, respectively. Emergency staff assessment was statistically independent from the likelihood of having a therapeutic antipsychotic level.

IMPLICATIONS

In patients presenting to emergency rooms with exacerbations of psychosis who are subsequently admitted to an inpatient facility, common assessments of medication status are frequently misleading. Readily available methods for rapidly measuring antipsychotic plasma levels in clinical settings are needed for clinicians to make reliable assessments.

Access to credible information on schizophrenia patients' medication adherence by prescribers can change their treatment strategies: evidence from an online survey of providers

OBJECTIVE

Overestimating patients' medication adherence diminishes the ability of psychiatric care providers to prescribe the most effective treatment and to identify the root causes of treatment resistance in schizophrenia. This study was conducted to determine how credible patient drug adherence information (PDAI) might change prescribers' treatment decisions.

METHODS

In an online survey containing 8 clinical case vignettes describing patients with schizophrenia, health care practitioners who prescribe antipsychotics to patients with schizophrenia were instructed to choose a preferred treatment recommendation from a set of predefined pharmacologic and non-pharmacologic options. The prescribers were randomly assigned to an experimental or a control group, with only the experimental group receiving PDAI. The primary outcome was the prescribers' treatment choice for each case. Between-group differences were analyzed using multinomial logistic regression.

RESULTS

A convenience sample (n=219) of prescribers completed the survey. For 3 nonadherent patient vignettes, respondents in the experimental group were more likely to choose a long-acting injectable antipsychotic compared with those in the control group (77.7% experimental vs 25.8% control; P<0.001). For 2 adherent but poorly controlled patient vignettes, prescribers who received PDAI were more likely to increase the antipsychotic dose compared with the control group (49.1% vs 39.1%; P<0.001). For the adherent and well-controlled patient vignette, respondents in both groups made similar treatment recommendations across all choices (P=0.099), but respondents in the experimental arm were more likely to recommend monitoring clinical stability (87.2% experimental vs 75.5% control, reference group).

CONCLUSION

The results illustrate how credible PDAI can facilitate more appropriate clinical decisions for patients with schizophrenia.

Changes in psychopathology in schizophrenia patients starting treatment with new-generation antipsychotics: therapeutic drug monitoring in a naturalistic treatment setting

Previous studies on the relationship between plasma levels of new-generation antipsychotics (NGAs) and clinical response did not account for inter- and intra-individual variability in drug levels. Therefore, the present study calculated the ratio of observed versus expected NGA plasma levels and investigated its relationship with changes in the Positive and Negative Syndrome Scale (PANSS). Data of patients starting monotherapy with a NGA were collected 2, 4, 8, and 12 weeks after initiation of treatment. Next to the assessment of changes in psychopathology (PANSS) the ratio of observed versus expected plasma level was calculated. A total number of 221 ratios were eligible for analysis. About half of them ranged from 0.5-2 and were considered "normal", whereas the others were considered either "too low" or "too high". Psychopathological symptoms improved over the course of treatment, but changes in PANSS from baseline did not correlate significantly with the ratios of observed versus expected plasma levels at any assessment. The lack of linear correlation can be explained by the fact that 92% of the observed NGA plasma levels were at ≥ 50% of the lower limit of the therapeutic reference range, i.e., within the asymptote of the logistic plasma level-effect relationship. Accordingly, our findings indicate that the great majority of patients were treated with NGA doses that led to optimal plasma levels, based on the clinical impression of the treating psychiatrist only. Thus, calculating the ratio of observed versus expected plasma level may not be necessary in a routine clinical setting.

Early treatment response predicted subsequent clinical response in patients with schizophrenia taking paliperidone extended-release

This 6-week open-labeled study investigated whether early treatment response in patients receiving paliperidone extended-release (paliperidone ER) can facilitate prediction of responses at Week 6. Patients with schizophrenia or schizoaffective disorder were administered 9mg/day of paliperidone ER during the first 2 weeks, after which the dose was adjusted clinically. They were assessed on Days 0, 4, 7, 14, 28, and 42 by the Positive and Negative Syndrome Scale (PANSS). The serum concentrations of 9-hydroxyrisperidone were examined on Days 14 and 42. Among the 41 patients enrolled, 26 were classified as responders (≧50% improvement on total PANSS scores at Week 6). In the receiver-operator curves (ROC) analyses, the changes in total PANSS scores at Week 2 appeared to show more accurate predictability compared to Day 4 and Day 7. At Week 6, no significant correlation was observed between blood 9-hydroxyrisperidone concentration and the total score or changes of PANSS scores. The results suggest that early treatment response to paliperidone ER, particularly at Week 2, can serve as a suitable outcome predictor at Week 6. Using 9mg/day paliperidone ER as an initial dose for schizophrenia treatment exhibited relatively favorable tolerability and feasibility.

Schizophrenia

Schizophrenia is a chronic psychiatric disorder with a heterogeneous genetic and neurobiological background that influences early brain development, and is expressed as a combination of psychotic symptoms - such as hallucinations, delusions and disorganization - and motivational and cognitive dysfunctions. The mean lifetime prevalence of the disorder is just below 1%, but large regional differences in prevalence rates are evident owing to disparities in urbanicity and patterns of immigration. Although gross brain pathology is not a characteristic of schizophrenia, the disorder involves subtle pathological changes in specific neural cell populations and in cell-cell communication. Schizophrenia, as a cognitive and behavioural disorder, is ultimately about how the brain processes information. Indeed, neuroimaging studies have shown that information processing is functionally abnormal in patients with first-episode and chronic schizophrenia. Although pharmacological treatments for schizophrenia can relieve psychotic symptoms, such drugs generally do not lead to substantial improvements in social, cognitive and occupational functioning. Psychosocial interventions such as cognitive-behavioural therapy, cognitive remediation and supported education and employment have added treatment value, but are inconsistently applied. Given that schizophrenia starts many years before a diagnosis is typically made, the identification of individuals at risk and those in the early phases of the disorder, and the exploration of preventive approaches are crucial.

Antipsychotic therapeutic drug monitoring: psychiatrists' attitudes and factors predicting likely future use

BACKGROUND

This study aimed to explore predictive factors for future use of therapeutic drug monitoring (TDM) and to further examine psychiatrists' current prescribing practices and perspectives regarding antipsychotic TDM using plasma concentrations.

METHOD

A cross-sectional study for consultant psychiatrists using a postal questionnaire was conducted in north-west England. Data were combined with those of a previous London-based study and principal axis factor analysis was conducted to identify predictors of future use of TDM.

RESULTS

Most of the 181 participants (82.9%, 95% confidence interval 76.7-87.7%) agreed that 'if TDM for antipsychotics were readily available, I would use it'. Factor analysis identified five factors from the original 35 items regarding TDM. Four of the factors significantly predicted likely future use of antipsychotic TDM and together explained 40% of the variance in a multivariate linear regression model. Likely future use increased with positive attitudes and expectations, and decreased with potential barriers, negative attitudes and negative expectations. Scientific perspectives of TDM and psychiatrist characteristics were not significant predictors.

CONCLUSION

Most senior psychiatrists indicated that they would use antipsychotic TDM if available. However, psychiatrists' attitudes and expectations and the potential barriers need to be addressed, in addition to the scientific evidence, before widespread use of antipsychotic TDM is likely in clinical practice.

Olanzapine and risperidone plasma concentration therapeutic drug monitoring: A feasibility study

BACKGROUND

This study aimed to develop a clinically acceptable method of therapeutic drug monitoring (TDM) for olanzapine and risperidone and to evaluate the feasibility of its implementation.

METHOD

A non-randomised study of inpatients from five Mental Health Trusts was conducted, with a clinical interview at the time of TDM and a subsequent 6-week follow-up review of clinical notes. The TDM intervention comprised: (a) a venous blood sample taken 12 hours post-dose, 7-10 days after drug initiation, and (b) rapid results feedback, with interpretation algorithm guidance.

RESULTS

Thirty-two participants provided samples (19 prescribed olanzapine, 13 risperidone). Twenty-six participants remained on the target drug at study end, with seven experiencing a dose change, for whom only four of the TDM results were confirmed as having been checked. Mean dose increased for olanzapine (0.9 mg/day, range 0-10) and decreased for risperidone (-0.3 mg/day, range -4-3).

CONCLUSION

TDM can be implemented as part of routine clinical practice for both drugs. However, the lack of robust supporting evidence for or against antipsychotic TDM has probably led to a lack of enthusiasm for and interest in the results. Nevertheless, the advent of less invasive measures and the targeting of patients who might be more likely to benefit may facilitate uptake.

California State Hospital Violence Assessment and Treatment (Cal-VAT) guidelines

Here we provide comprehensive guidelines for the assessment and treatment of violence and aggression of various etiologies, including psychotic aggression and impulsive aggression due to schizophrenia, mood disorders, ADHD, or trauma, and predatory aggression due to psychopathy and other personality disorders. These guidelines have been developed from a collection of prescribing recommendations, clinical trial results, and years of clinical experience in treating patients who are persistently violent or aggressive in the California Department of State Hospital System. Many of the recommendations provided in these guidelines employ off-label prescribing practices; thus, sound clinical judgment based on individual patient needs and according to institution formularies must be considered when applying these guidelines in clinical practice.