Estimating the optimal dose of flupentixol decanoate in the maintenance treatment of schizophrenia-a systematic review of the literature

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: Focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialised tools are used. Three tools have been proven useful to personalise drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimise treatment effects, minimise side effects and ultimately reduce the global burden of diseases, personalised drug treatment has not yet become the standard of care in psychiatry.

Using in silico methods to determine optimal tapering regimens for decanoate-based long-acting injectable psychosis drugs

Background

Reducing the dose of psychosis drugs in a gradual hyperbolic manner may minimise withdrawal effects and risk of relapse. There is presently limited guidance on tapering decanoate-based long-acting injectable dopamine antagonists (LIDAs).

Objectives

We aimed to apply hyperbolic principles of tapering to the decanoate-based LIDAs flupentixol, zuclopenthixol and haloperidol to develop withdrawal regimens.

Design

We used in silico methodology to predict plasma drug levels and D2 occupancy for different LIDA regimens.

Methods

Existing pharmacokinetic and receptor occupancy data from nuclear neuroimaging studies were used to power modelling. Abrupt discontinuation was examined as a potential strategy, and dose reduction was modelled with pre-defined constraints used in similar work of 10 (fast regimens), 5 (moderate) and 2.5 (slow) percentage points of D2 occupancy change per month.

Results

Abrupt discontinuation of decanoate-based LIDAs leads to excessive change in D2 occupancy which violated our pre-defined constraints, potentially resulting in withdrawal symptoms and increased risk of relapse. Reduction of LIDA dose allowed hyperbolic reduction in plasma level consistent with imposed constraints on receptor occupancy reduction rate. For equivalent per-weekly LIDA dosing, more frequent administration allowed a more gradual reduction of D2 occupancy. However, switching to oral forms is required to continue hyperbolic tapering to full discontinuation; reduction to zero using only LIDA produces too large a reduction in D2 occupancy. Guidance for reduction and cessation of LIDAs according to slow, moderate and fast criteria is provided.

Conclusion

Abrupt cessation of decanoate LIDAs is not consistent with gradual hyperbolic tapering, despite their longer half-lives compared with oral formulations. Reduction to the point of full discontinuation can only be achieved by switching to oral therapy to complete the taper. These results are limited by the in silico and theoretical nature of the study, and there is a need to confirm these findings through real-world observational and interventional studies.

Reimagining old drugs with new tricks: Mechanisms, strategies and notable success stories in drug repurposing for neurological diseases

Recent evolution in drug repurposing has brought new anticipation, especially in the conflict against neurodegenerative diseases (NDDs). The traditional approach to developing novel drugs for these complex disorders is laborious, time-consuming, and often abortive. However, drug reprofiling which is the implementation of illuminating novel therapeutic applications of existing approved drugs, has shown potential as a promising strategy to accelerate the hunt for therapeutics. The advancement of computational approaches and artificial intelligence has expedited drug repurposing. These progressive technologies have enabled scientists to analyse extensive datasets and predict potential drug-disease interactions. By prospecting into the existing pharmacological knowledge, scientists can recognise potential therapeutic candidates for reprofiling, saving precious time and resources. Preclinical models have also played a pivotal role in this field, confirming the effectiveness and mechanisms of action of repurposed drugs. Several studies have occurred in recent years, including the discovery of available drugs that demonstrate significant protective effects in NDDs, relieve debilitating symptoms, or slow down the progression of the disease. These findings highlight the potential of repurposed drugs to change the landscape of NDD treatment. Here, we present an overview of recent developments and major advances in drug repurposing intending to provide an in-depth analysis of traditional drug discovery and the strategies, approaches and technologies that have contributed to drug repositioning. In addition, this chapter attempts to highlight successful case studies of drug repositioning in various therapeutic areas related to NDDs and explore the clinical trials, challenges and limitations faced by researchers in the field. Finally, the importance of drug repositioning in drug discovery and development and its potential to address discontented medical needs is also highlighted.

A proposal for reducing maximum target doses of drugs for psychosis: Reviewing dose-response literature

BACKGROUND

Presently, there is limited guidance on the maximal dosing of psychosis drugs that is based on effectiveness rather than safety or toxicity. Current maximum dosing recommendations may far exceed the necessary degree of dopamine D2 receptor blockade required to treat psychosis. This may lead to excess harm through cognitive impairment and side effects.

AIMS

This analysis aimed to establish guidance for prescribers by optimally dosing drugs for psychosis based on efficacy and benefit.

METHODS

We used data from two dose-response meta-analyses and reviewed seven of the most prescribed drugs for psychosis in the UK. Where data were not available, we used appropriate comparison techniques based on D2 receptor occupancy to extrapolate our recommendations.

RESULTS

We found that the likely threshold dose for achieving remission of psychotic symptoms was often significantly below the currently licensed dose for these drugs. We therefore recommend that clinicians are cautious about exceeding our recommended doses. Individual factors, however, should be accounted for. We outline potentially relevant factors including age, ethnicity, sex, smoking status and pharmacogenetics. Additionally, we recommend therapeutic drug monitoring as a tool to determine individual pharmacokinetic variation.

CONCLUSIONS

In summary, we propose a new set of maximum target doses for psychosis drugs based on efficacy. Further research through randomised controlled trials should be undertaken to evaluate the effect of reducing doses from current licensing maximums or from doses that are above our recommendations. However, dose reductions should be implemented in a manner that accounts for and reduces the effects of drug withdrawal.

Long-Acting Injectable Antipsychotics-A Review on Formulation and In Vitro Dissolution

Long-acting injectable (LAI) neuroleptics constitute an effective therapeutical alternative for individuals suffering from persistent mental illness. These injectable pharmaceuticals help patients manage their condition better and improve long-term outcomes by preventing relapses and improving compliance. This review aims to analyse the current formulation aspects of LAI neuroleptics, with particular emphasis on analysis of drug release profiles as a critical test to guarantee drug quality and relevant therapeutical activity. While there is no officially approved procedure for depot parenteral drug formulations, various dissolution tests which were developed by LAI manufacturers are described. In vitro dissolution tests also possess a critical function in the estimation of the in vivo performance of a drug formulation. For that reason, thorough inspection of the in vitro-in vivo correlation (IVIVC) is also discussed.

Current and emerging long-acting antipsychotics for the treatment of schizophrenia

Introduction: In this review, the authors discuss the role of long-acting injectable antipsychotics (LAIs) for schizophrenia, focusing on the effectiveness and new perspectives introduced by such treatment strategy. Despite their promising pharmacokinetic features and their potential advantages in medication adherence, clinical outcomes, and medical costs, LAIs are not habitually presented as an option for patients, especially in the early phase of schizophrenia.Areas covered: This review explores the panorama of available LAIs for the treatment of schizophrenia, first-episode of psychosis, approved indications, medical costs, medication adherence, side effects, effectiveness and differences between first-generation (FGA)-LAIs and second-generation (SGA)-LAIs.Expert Opinion: LAIs differ in terms of specific indications, approved injection sites, needle size, injection volume, injection interval as well as potential drug-drug interactions, and commonly reported adverse reactions. The approved indications have expanded beyond schizophrenia to include bipolar and schizoaffective disorder. SGA-LAIs are often preferred to FGA-LAIs. FGA-LAIs although are less chosen in new patients due to the induction of cognitive and extrapyramidal side effects, even if, on the other hand, many SGA-LAIs are burden by hyperprolactinemia and weight gain. After a review of the available evidence, insight is provided into the potential and current therapeutic opportunities offered by LAI antipsychotic formulations.

Therapeutic Drug Monitoring of Long-Acting Injectable Antipsychotic Drugs

BACKGROUND

The use of therapeutic drug monitoring (TDM) to guide treatment with long-acting injectable (LAI) antipsychotics, which are increasingly prescribed, remains a matter of debate. The aim of this review was to provide a practical framework for the integration of TDM when switching from an oral formulation to the LAI counterpart, and in maintenance treatment.

METHODS

The authors critically reviewed 3 types of data: (1) positron emission tomography data evaluating dopamine (D2/D3) receptor occupancy related to antipsychotic concentrations in serum or plasma; D2/D3 receptors are embraced as target sites in the brain for antipsychotic efficacy and tolerability, (2) pharmacokinetic studies evaluating the switch from oral to LAI antipsychotics, and (3) pharmacokinetic data for LAI formulations. Based on these data, indications for TDM and therapeutic reference ranges were considered for LAI antipsychotics.

RESULTS

Antipsychotic concentrations in blood exhibited interindividual variability not only under oral but also under LAI formulations because these concentrations are affected by demographic characteristics such as age and sex, genetic peculiarities, and clinical variables, including comedications and comorbidities. Reported data combined with positron emission tomography evidence indicated a trend toward lower concentrations under LAI administration than under oral medications. However, the available evidence is insufficient to recommend LAI-specific therapeutic reference ranges.

CONCLUSIONS

Although TDM evidence for newer LAI formulations is limited, this review suggests the use of TDM when switching an antipsychotic from oral to its LAI formulation. The application of TDM practice is more accurate for dose selection than the use of dose equivalents as it accounts more precisely for individual characteristics.

Side-effect monitoring of continuing LAI antipsychotic medication in UK adult mental health services

BACKGROUND

Long-acting injectable (LAI) antipsychotic medications are used to optimise treatment outcomes in schizophrenia. Guaranteed medication delivery increases the responsibility of prescribers to monitor and manage adverse effects.

METHODS

In the context of a quality improvement programme conducted by the Prescribing Observatory for Mental Health, a clinical audit addressed documented side-effect monitoring in patients prescribed continuing LAI antipsychotic medication under the care of United Kingdom adult mental health services.

RESULTS

A total of 62 mental health services submitted data on 5169 patients prescribed LAI antipsychotic medication for more than a year. An assessment of side effects had been documented in the past year in 2304 (45%) cases. Post hoc analysis showed that extrapyramidal side effects were more likely to have been assessed and found to be present in those patients prescribed LAI haloperidol, flupentixol or zuclopenthixol. There was little other targeting of assessments to the known side effects profiles of individual LAI antipsychotic medications, but when dysphoria had been assessed it was most commonly found with LAI haloperidol treatment and when weight gain, sexual and prolactin-related side effects had been assessed, they were more often identified with LAI paliperidone.

CONCLUSION

The data suggest a relatively low frequency of side-effect assessments, largely untargeted. This is likely to result in many adverse effects going unrecognised and unmanaged, thus failing to tackle their potential to confound mental state assessment and adversely affect physical health and adherence. Patients receiving LAI antipsychotic medication have regular contact with a healthcare professional who administers the medication, which provides an opportunity to potentially remedy this situation.

Pharmacokinetic Characteristics of Long-Acting Injectable Antipsychotics for Schizophrenia: An Overview

The availability of long-acting injectable (LAI) antipsychotics for the treatment of schizophrenia provides clinicians with options that deliver continuous drug exposure and may improve adherence compared with daily oral antipsychotics. However, all LAI antipsychotics have unique formulations and pharmacokinetic characteristics that have implications for medication selection, administration interval, and injection site. This review outlines key differences in drug formulations and pharmacokinetics among LAI antipsychotics. A systematic search of the PubMed database was conducted to identify physical and formulation properties and pharmacokinetic data of commercially available LAI antipsychotics, including flupentixol decanoate, fluphenazine decanoate, haloperidol decanoate, zuclopenthixol decanoate, aripiprazole monohydrate, aripiprazole lauroxil, olanzapine pamoate, paliperidone palmitate, risperidone microspheres, and risperidone polymeric microspheres. Additional information was obtained from package inserts and product monographs. Relevant data on drug properties, administration details, pharmacokinetic parameters, and oral dose equivalencies of LAI antipsychotics are summarized. Based on our analysis, formulation characteristics (e.g., vehicle medium) and administration characteristics (e.g., injection site) can affect rate of absorption and adverse effects and may factor into whether oral supplementation or an additional injection is needed. Dose adjustments may be necessary based on potential drug-drug interactions, and approximate dose equivalence with oral formulations can help inform titration when switching from oral to LAI formulations. Clinicians administering LAI antipsychotics should consider these formulation and pharmacokinetic factors to maximize clinical impact and to adjust to an individual patient's needs and treatment goals.

Newer Formulations of Risperidone: Role in the Management of Psychotic Disorders

Antipsychotic long-acting injections improve relapse prevention in psychotic disorders. Three new risperidone formulations have been developed that offer advantages over currently available risperidone-based long-acting injections. Risperidone ISM^® is a monthly intramuscular injection that does not require loading doses or concurrent oral risperidone. RBP-7000 is a monthly subcutaneous injection not requiring loading or oral supplementation. BB0817 is a 6-monthly implant of risperidone injected subcutaneously. All three preparations have been shown to be effective and well tolerated in clinical trials. A fourth formulation (TV-46000), which can be given subcutaneously every 1 or 2 months, has recently begun trials.