Risperidone. A review of its pharmacology and therapeutic potential in the treatment of schizophrenia

QT Interval, Antipsychotics and Correlates Among Patients with Schizophrenia: Cross-Sectional Data from the Multicentric Real-World FACE-SZ

BACKGROUND

The life expectancy of patients with schizophrenia is reduced, partly due to cardiovascular diseases. Antipsychotics are associated with QT interval prolongation, which is a risk factor for arrhythmia and cardiac arrest. The differences between antipsychotic with regard to QT interval prolongation are not well understood.

OBJECTIVE

The aim was to compare the QT values associated with different antipsychotics within a real-world population of subjects with clinically stable forms of schizophrenia.

METHODS

The FACE-SZ cohort comprises subjects with psychotic disorders, referred to schizophrenia expert cents. QT interval was measured, as well as all treatments (psychotropic and others). The following maintenance treatment for schizophrenia was analysed cross-sectionally: aripiprazole, clozapine, haloperidol, amisulpride, olanzapine, quetiapine, risperidone. Age, sex, smoking status, body mass index, blood potassium levels, and the co-prescription of another QT-prolonging treatment were used as adjustment factors in multivariable linear regression analyses.

RESULTS

Among 792 patients, the mean corrected QT (QTc) interval in the sample of patients under monotherapy was 407 ms. The mean age was 31.7 years, and the majority were male (73.3 %). In comparison to the rest of the sample, clozapine was associated with a longer QTc interval (β = 0.012, 95% CI [0.006-0.018]), while aripiprazole was significantly associated with a shorter QTc interval (β = - 0.010, 95% CI [- 0.016 to - 0.005]). Other antipsychotics were not associated with significant variations of the QTc.

CONCLUSIONS

The prescription of antipsychotics should always be accompanied by close monitoring of the QTc interval to prevent the risk of severe cardiac arrhythmia, particularly concerning clozapine.

Risperidone In Situ Microparticles: A Review in Schizophrenia

Risperidone in situ microparticles (risperidone ISM®) is a novel long-acting prolonged-release formulation approved in the EU and USA for treating schizophrenia in adults. Once-monthly intramuscular injections of risperidone ISM® provide immediate and sustained therapeutic levels of risperidone, eliminating the need for loading doses or oral supplementation. In the pivotal PRISMA-3 trial in patients with acute schizophrenia exacerbation, risperidone ISM® significantly improved Positive and Negative Syndrome Scale (primary endpoint) and Clinical Global Impression-Severity of Illness (key secondary endpoint) total scores over the 12-week double-blind phase, with improvements observed as early as day 8. Continued treatment sustained efficacy over the 12-month open-label extension phase. Risperidone ISM® also improved social functioning and had a positive impact on health-related quality of life. Patients stable on daily oral risperidone maintained their treatment benefits after switching to monthly risperidone ISM®. Risperidone ISM® was generally well tolerated in clinical trials, with a safety profile consistent with that of oral risperidone. Its fast onset of action, without the need for oral supplementation or loading doses, makes risperidone ISM® a promising long-acting injectable that could enhance treatment adherence.

Agitation: Neurobiology and current management guidelines

There have been important updates in the guidelines for the management of agitation in emergency room settings, including psychiatric emergency services. This manuscript provides a synthesis of current recommendations, combined with a detailed breakdown of the neurobiology of agitation, linking these neuroscientific dimensions with the pharmacological profiles of the drugs recommended by practice guidelines (as well as the profiles of other important agents). Since Project BETA (Best Practices in Evaluation and Treatment of Agitation) guidelines were published in 2012 (by the American Association for Emergency Psychiatry), there have been several developments in the standard of care, including an increase in use of ketamine and droperidol. Recommended treatment strategies for clinicians will be presented, including consideration of how to address specific causes of agitation.

Sustainable and Safe N-alkylation of N-heterocycles by Propylene Carbonate under Neat Reaction Conditions

A new, eco-friendly process utilising the green solvent propylene carbonate (PC) has been developed to perform N-alkylation of N-, O- and/or S-containing heterocyclic compounds. PC in these reactions served as both the reagent and solvent. Importantly, no genotoxic alkyl halides were required. No auxiliary was necessary when using anhydrous PC. Product formation includes nucleophilic substitution with the concomitant loss of water and carbon dioxide. Substrates prepared, including the newly invented PROTAC drugs, are widely used.

A preclinical secondary pharmacology resource illuminates target-adverse drug reaction associations of marketed drugs

In vitro secondary pharmacology assays are an important tool for predicting clinical adverse drug reactions (ADRs) of investigational drugs. We created the Secondary Pharmacology Database (SPD) by testing 1958 drugs using 200 assays to validate target-ADR associations. Compared to public and subscription resources, 95% of all and 36% of active (AC50 < 1 µM) results are unique to SPD, with bias towards higher activity in public resources. Annotating drugs with free maximal plasma concentrations, we find 684 physiologically relevant unpublished off-target activities. Furthermore, 64% of putative ADRs linked to target activity in key literature reviews are not statistically significant in SPD. Systematic analysis of all target-ADR pairs identifies several putative associations supported by publications. Finally, candidate mechanisms for known ADRs are proposed based on SPD off-target activities. Here we present a freely-available resource for benchmarking ADR predictions, explaining phenotypic activity and investigating clinical properties of marketed drugs.

Neuropharmacological effect of risperidone: From chemistry to medicine

As the second-oldest atypical antipsychotic, risperidone has a long history of off-label usage for treating behavioural and psychological signs and symptoms of dementia (BPSD), such as agitation, aggressiveness, and psychosis. Risperidone has been shown in several trials to have a statistically significant benefit when used in a therapeutic context. Several lines of evidence suggest a possible role of risperidone via the antagonistic effect of Dopamine D2 and 5HT-receptor in different neurological diseases like cognitive dysfunction of schizophrenia, neuroinflammation, Huntington's disease, and sleep cycle management. Therefore, the pharmacological interactions of risperidone in all these diseases were investigated. Some reports on the use of risperidone in the treatment of dopaminergic psychosis have been slightly conflicting. However, more research is needed to evaluate the role of risperidone in the treatment of these neurological diseases.

Nanocarrier-Based Drug Delivery to Brain: Interventions of Surface Modification

Brain disorders are a prevalent and rapidly growing problem in the medical field as they adversely affect the quality of life of a human. With an increase in life expectancy, it has been reported that diseases like Alzheimer's, Parkinson's, stroke and brain tumors, along with neuropsychological disorders, are also being reported at an alarmingly high rate. Despite various therapeutic methods for treating brain disorders, drug delivery to the brain has been challenging because of a very complex Blood Brain Barrier, which precludes most drugs from entering the brain in effective concentrations. Nano-carrier-based drug delivery systems have been reported widely by researchers to overcome this barrier layer. These systems due to their small size, offer numerous advantages; however, their short residence time in the body owing to opsonization hinders their success in vivo. This review article focuses on the various aspects of modifying the surfaces of these nano-carriers with polymers, surfactants, protein, antibodies, cell-penetrating peptides, integrin binding peptides and glycoproteins such as transferrin & lactoferrin leading to enhanced residence time, desirable characteristics such as the ability to cross the blood-brain barrier (BBB), increased bioavailability in regions of the brain and targeted drug delivery.

Understanding the Effects of Antipsychotics on Appetite Control

Antipsychotic drugs (APDs) represent a cornerstone in the treatment of schizophrenia and other psychoses. The effectiveness of the first generation (typical) APDs are hampered by so-called extrapyramidal side effects, and they have gradually been replaced by second (atypical) and third-generation APDs, with less extrapyramidal side effects and, in some cases, improved efficacy. However, the use of many of the current APDs has been limited due to their propensity to stimulate appetite, weight gain, and increased risk for developing type 2 diabetes and cardiovascular disease in this patient group. The mechanisms behind the appetite-stimulating effects of the various APDs are not fully elucidated, partly because their diverse receptor binding profiles may affect different downstream pathways. It is critical to identify the molecular mechanisms underlying drug-induced hyperphagia, both because this may lead to the development of new APDs, with lower appetite-stimulating effects but also because such insight may provide new knowledge about appetite regulation in general. Hence, in this review, we discuss the receptor binding profile of various APDs in relation to the potential mechanisms by which they affect appetite.

The Opioid Interactions of the Antipsychotic Medications Risperidone and Amisulpride in Mice and Their Potential Use in the Treatment of Other Non-Psychotic Medical Conditions

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. The opioid epidemic in the USA has highlighted the need for alternative treatments for pain. Following reports on the opioid interactions of various antipsychotic medications, we speculated that the involvement of the opioid system in some of the antipsychotics' mechanism of action may suggest their potential use in the treatment of pain. Risperidone is a neuroleptic with a potent dopamine D2 and serotonin 5-HT2 receptor-blocking activity as well as a high affinity for adrenergic and histamine H1 receptors. Amisulpride is a neuroleptic which selectively blocks dopamine D2 and D3 receptors. Both had a potent antinociceptive effect on ICR mice tested with a tail flick assay. That effect on both medications was antagonized by naloxone, indicating that at least some of the antinociceptive effects were mediated by an opioid mechanism of action. Further investigation found that β-Funaltrexamine hydrochloride (β-FNA), naloxonazine, and nor-Binaltorphimine dihydrochloride (nor-BNI) reversed the antinociceptive effect of both risperidone and amisulpride. Naltrindole at a dose that blocked [D-Pen2,D-Pen5]enkephalin (DPDPE, δ analgesia) blocked notably amisplride effect and only partially reversed that of risperidone. Risperidone induced an antinociceptive effect, implying involvement of μ and κ-opioid and δ-opioid mechanisms. Amisulpride-induced antinociception was mediated through selective involvement of all three opioid receptor subtypes. These findings emphasize the need for clinical trials to assess the possibility of extending the spectrum of medications available for the treatment of pain.

Multitarget-directed therapeutics: (Urea/thiourea)2 derivatives of diverse heterocyclic-Lys conjugates

The synthesis of a new small library of molecules containing bis-urea/thiourea pendants in lysine conjugated to three different heterocycles is described. The heterocycles used in this study have benzisoxazole/piperazine/piperidine units. After a detailed antimicrobial, antioxidant, and anti-inflammatory evaluation, it was found that the most active compounds are 10, 11, 14, 15, 18, 19 and 10, 11, 19 and 8, 9, 12, 13, 16, 17, respectively. Further, it was observed that the presence of all three entities, that is, urea/thiourea, the substituent (OMe/F), as well as the heterocycle, is highly essential for exerting potent activity. Among the heterocycles, the presence of isoxazole seems to be highly beneficial for exerting good potency. In continuation, docking studies have revealed extraordinary binding efficiency for some of the active compounds. Given their potent biological results and docking score, some of the title compounds could be potential drug candidates for microbial-related diseases and provide a basis for future research into the development of molecules possessing multitask ability.

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.

Risperidone stimulates food intake and induces body weight gain via the hypothalamic arcuate nucleus 5-HT2c receptor-NPY pathway

Aims

Many patients taking risperidone for the treatment of psychiatric disorders experience substantial body weight gain. Researchers have speculated that risperidone induces obesity by modulating central signals; however, the precise central mechanisms involved remain to be fully elucidated.

Methods

Twenty‐four C57BL/6J mice were divided into four groups: a control group; a risperidone‐treated group; a lorcaserin‐treated group; and a combined risperidone + lorcaserin‐treated group. The mice were received the corresponding treatments for 4 weeks, and their brains were collected for in situ hybridization analysis. A subset of C57BL/6J mice was administrated with risperidone or placebo, and brains were collected 60 minutes post‐treatment for determination of c‐fos activity. In addition, brains of NPY‐GFP mice treated with or without risperidone were collected to perform colocalization of NPY and c‐fos, as well as NPY and 5‐HT2c receptor using immunohistochemistry.

Results

There was significantly elevated c‐fos expression in the hypothalamic arcuate nucleus (Arc) of risperidone‐treated mice. More than 68% c‐fos‐positive neurons were NPY‐expressing neurons. Furthermore, in situ hybridization revealed that Arc NPY mRNA expression was significantly increased in the risperidone‐treated group compared with control group. Moreover, we identified that 95% 5‐HT2c receptors were colocalized with NPY positive neurons, and increased Arc NPY mRNA expression induced by risperidone was markedly reduced by cotreatment with lorcaserin, a specific 5‐HT2c receptor agonist.

Conclusion

Our findings provide critical insight into the mechanisms underlying antipsychotic‐induced obesity, which may assist the development of therapeutic strategies to address metabolic side effects of risperidone.

Altered levels of dopamine transporter in the frontal pole and dorsal striatum in schizophrenia

The dopamine hypothesis proposes that there is a hypodopaminergic state in the prefrontal cortex and a hyperdopaminergic state in the striatum of patients with schizophrenia. Evidence suggests the hyperdopaminergic state in the striatum is due to synaptic dopamine elevation, particularly in the dorsal striatum. However, the molecular mechanisms causing disrupted dopaminergic function in schizophrenia remains unclear. We postulated that the dopamine transporter (DAT), which regulates intra-synaptic dopamine concentrations by transporting dopamine from the synaptic cleft into the pre-synaptic neuron, could be involved in dopaminergic dysfunction in schizophrenia. Therefore, we measured levels of DAT in the cortex and striatum from patients with schizophrenia and controls using postmortem human brain tissue. Levels of desmethylimipramine-insensitive mazindol-sensitive [³H]mazindol binding to DAT were measured using in situ radioligand binding and autoradiography in gray matter from Brodmann’s area (BA) 10, BA 17, the dorsal striatum, and nucleus accumbens from 15 patients with schizophrenia and 15 controls. Levels of desmethylimipramine-insensitive mazindol-sensitive [³H]mazindol binding were significantly higher in BA 10 from patients with schizophrenia (p = 0.004) and significantly lower in the dorsal striatum (dorsal putamen p = 0.005; dorsal caudate p = 0.007) from those with the disorder. There were no differences in levels of desmethylimipramine-insensitive [³H]mazindol binding in BA 17 or nucleus accumbens. These data raise the possibility that high levels of DAT in BA 10 could be contributing to lower synaptic cortical dopamine, whereas lower levels of DAT could be contributing to a hyperdopaminergic state in the dorsal striatum.

Pharmacological Therapy in Panic Disorder: Current Guidelines and Novel Drugs Discovery for Treatment-resistant Patient

Panic disorder (PD) being one of the most intensively investigated anxiety disorders is considered a heterogeneous psychiatric disease which has difficulties with early diagnosis. The disorder is recurrent and usually associated with low remission rates and high rates of relapse which may exacerbated social and quality of life, causes unnecessary cost and increased risk for complication and suicide. Current pharmacotherapy for PD are available but these drugs have slow therapeutic onset, several side effects and most patients do not fully respond to these standard pharmacological treatments. Ongoing investigations indicate the need for new and promising agents for the treatment of PD. This article will cover the importance of immediate and proper treatment, the gap in the current management of PD with special emphasis on pharmacotherapy, and evidence regarding the novel anti-panic drugs including the drugs in developments such as metabotropic glutamate (mGlu 2/3) agonist and levetiracetam. Preliminary results suggest the anti-panic properties and the efficacy of duloxetine, reboxetine, mirtazapine, nefazodone, risperidone and inositol as a monotherapy drug. Apart for their effectiveness, the aforementioned compounds were generally well tolerated compared to the standard available pharmacotherapy drugs, indicating their potential therapeutic usefulness for ambivalent and hypervigilance patient. Further strong clinical trials will provide an ample support to these novel compounds as an alternative monotherapy for PD treatment-resistant patient.

A randomised controlled trial of vitamin D and omega-3 long chain polyunsaturated fatty acids in the treatment of irritability and hyperactivity among children with autism spectrum disorder

Irritability and hyperactivity are common in children with Autism Spectrum Disorder (ASD). Because pharmacological treatments may have adverse effects, and despite limited evidence, caregivers/parents often use dietary supplements such as vitamin D and omega-3 fatty acids to address these behavioural symptoms. As a secondary objective of the VIDOMA (Vitamin D and Omega-3 in ASD) trial, we evaluated the efficacy of vitamin D, omega-3 long chain polyunsaturated fatty acid [omega-3 LCPUFA; docosahexaenoic acid (DHA)], or both on irritability and hyperactivity. New Zealand children with ASD (aged 2.5-8 years) participated in a 12-month randomized, double-blind, placebo-controlled trial of vitamin D (2000 IU/day, VID), omega-3 LCPUFA (722 mg/day DHA, OM), or both (2000 IU/day vitamin D + 722 mg/day DHA, VIDOM). The primary outcomes were the Aberrant Behaviour Checklist (ABC) domains of irritability and hyperactivity. Biomarkers (serum 25-hydroxyvitamin D [25(OH)D] and omega-3 index) and primary outcomes were measured at baseline and 12-months. Out of 111 children who completed baseline data collection, 66% completed the study (VID = 19, OM = 23, VIDOM = 15, placebo = 16). After 12 months, children receiving OM (-5.0 ± 5.0, P = 0.001) and VID (-4.0±4.9, P = 0.01) had greater reduction in irritability than placebo (0.8±6.1). Compared to placebo, children on VID also had greater reduction in hyperactivity (-5.2±6.3 vs. -0.8±5.6, P = 0.047). Serum 25(OH)D concentration (nmol/L, mean±SD) increased by 27±14 in VID and by 36±17 in VIDOM groups (P < 0.0001), and omega-3 index (%, median (25th, 75th percentiles)) by 4.4 (3.3, 5.9) in OM and by 4.0 (2.0, 6.0) in VIDOM groups (P < 0.0001), indicating a good compliance rate. The results indicate that vitamin D and omega-3 LCPUFA reduced irritability symptoms in children with ASD. Vitamin D also reduced hyperactivity symptoms in these children.

Current Concepts and Treatments of Schizophrenia

Schizophrenia is a debilitating mental illness which involves three groups of symptoms, i.e., positive, negative and cognitive, and has major public health implications. According to various sources, it affects up to 1% of the population. The pathomechanism of schizophrenia is not fully understood and current antipsychotics are characterized by severe limitations. Firstly, these treatments are efficient for about half of patients only. Secondly, they ameliorate mainly positive symptoms (e.g., hallucinations and thought disorders which are the core of the disease) but negative (e.g., flat affect and social withdrawal) and cognitive (e.g., learning and attention disorders) symptoms remain untreated. Thirdly, they involve severe neurological and metabolic side effects and may lead to sexual dysfunction or agranulocytosis (clozapine). It is generally agreed that the interactions of antipsychotics with various neurotransmitter receptors are responsible for their effects to treat schizophrenia symptoms. In particular, several G protein-coupled receptors (GPCRs), mainly dopamine, serotonin and adrenaline receptors, are traditional molecular targets for antipsychotics. Comprehensive research on GPCRs resulted in the exploration of novel important signaling mechanisms of GPCRs which are crucial for drug discovery: intentionally non-selective multi-target compounds, allosteric modulators, functionally selective compounds and receptor oligomerization. In this review, we cover current hypotheses of schizophrenia, involving different neurotransmitter systems, discuss available treatments and present novel concepts in schizophrenia and its treatment, involving mainly novel mechanisms of GPCRs signaling.

Response surface optimization, Ex vivo and In vivo investigation of nasal spanlastics for bioavailability enhancement and brain targeting of risperidone

Transnasal brain drug targeting could ensure better drug delivery to the brain through the olfactory pathway. Risperidone bioavailability is 66% in extensive metabolizers and 82% in slow metabolizers. The aim of this study is to investigate the ability of the nanovesicular spanlastics to effectively deliver risperidone through the nasal route to the brain and increase its bioavailability. Spanlastics formulae, composed of span and polyvinyl alcohol, were designed based on central composite statistical design. The planned formulae were prepared using ethanol injection method. The prepared formulae were characterized by testing their particle size, polydispersity index, zeta potential and encapsulation efficiency. The optimized formula having the lowest particle size, polydispersity index, the highest zeta potential and encapsulation efficiency was subjected to further investigations including characterization of its rheological properties, elasticity, transmission electron microscopy, in vitro diffusion, ex vivo permeation, histopathology and in vivo biodistribution. The optimized formula was composed of 5mg/mL span and 30mg/mL polyvinyl alcohol. It showed significantly higher transnasal permeation and better distribution to the brain, when compared to the used control regarding the brain targeting efficiency and the drug transport percentage (2.16 and 1.43 folds increase, respectively). The study introduced a successful and promising formula to directly and effectively carry the drug from nose to brain.

Likelihood of mechanistic roles for dopaminergic, serotonergic and glutamatergic receptors in tardive dyskinesia: A comparison of genetic variants in two independent patient populations

Objectives:

An established theory for the pathogenesis of tardive dyskinesia is disturbed dopaminergic receptor sensitivity and/or dopaminergic intracellular signaling. We examined associations between genetic variants of neurotransmitter receptors and tardive dyskinesia.

Methods:

We assessed tardive dyskinesia in Caucasian psychiatric inpatients from Siberia (N = 431) and a long-stay population from the Netherlands (N = 168). These patients were genotyped for 43 tag single nucleotide polymorphisms in five neurotransmitter receptor genes, and the results for the two populations were compared.

Results:

Several significant associations with tardive dyskinesia were identified, but only GRIN2A (rs1345423) was found in both patient populations. This lack of agreement was probably due to the small effect size of the associations, the multiple testing and the small sample size of the Dutch patient population. After reviewing the literature, we propose that the constitutive stimulatory activity of serotonergic type 2 receptors may be relevant.

Conclusions:

Inactivity of the serotonergic, type 2C receptor or blockade of these receptors by atypical antipsychotic drugs may decrease the vulnerability to develop tardive dyskinesia.

Individual differences in in vitro and in vivo metabolic clearances of antipsychotic risperidone from Japanese subjects genotyped for cytochrome P450 2D6 and 3A5

OBJECTIVE

There are conflicting reports regarding the effects of cytochrome P450 (P450, CYP) genotypes on the plasma concentrations of risperidone and its pharmacologically active metabolite, 9-hydroxyrisperidone (paliperidone), in clinical patients. The aim of this study was to investigate individual differences in the metabolic clearance of risperidone in vitro and in vivo.

METHODS

In vitro liver microsomal risperidone 9-hydroxylation activities and in vivo plasma concentrations of risperidone and paliperidone were investigated in 15 male and 12 female Japanese subjects (mean age 52 years, range: 24-75 years) genotyped for CYP2D6 and CYP3A5.

RESULTS

CYP2D6 intermediate and poor metabolizers showed significantly lower liver microsomal risperidone 9-hydroxylation activities than extensive metabolizers did at 5 μM of risperidone; this difference was not evident at 50 μM of risperidone. The recombinant CYP3A5 Vmax/Km value for risperidone 9-hydroxylation was 30% that of CYP3A4, and liver microsomes from CYP3A5 expressers had similar risperidone 9-hydroxylation activities to those of CYP3A5 poor expressers. The plasma concentration/dose ratios for risperidone and paliperidone in 27 Japanese patients were not significantly influenced by the CYP2D6 or CYP3A5 genotypes.

CONCLUSIONS

Individual differences in metabolic clearance of risperidone under the present conditions were not significantly influenced by the genotypes of CYP2D6 or CYP3A5.

Development of Risperidone PLGA Microspheres

The aim of this study was to design and evaluate biodegradable PLGA microspheres for sustained delivery of Risperidone, with an eventual goal of avoiding combination therapy for the treatment of schizophrenia. Two PLGA copolymers (50 : 50 and 75 : 25) were used to prepare four microsphere formulations of Risperidone. The microspheres were characterized by several in vitro techniques. In vivo studies in male Sprague-Dawley rats at 20 and 40 mg/kg doses revealed that all formulations exhibited an initial burst followed by sustained release of the active moiety. Additionally, formulations prepared with 50 : 50 PLGA had a shorter duration of action and lower cumulative AUC levels than the 75 : 25 PLGA microspheres. A simulation of multiple dosing at weekly or 15-day regimen revealed pulsatile behavior for all formulations with steady state being achieved by the second dose. Overall, the clinical use of Formulations A, B, C, or D will eliminate the need for combination oral therapy and reduce time to achieve steady state, with a smaller washout period upon cessation of therapy. Results of this study prove the suitability of using PLGA copolymers of varying composition and molecular weight to develop sustained release formulations that can tailor in vivo behavior and enhance pharmacological effectiveness of the drug.

Bioequivalence and pharmacokinetic evaluation of two formulations of risperidone 2 mg : an open-label, single-dose, fasting, randomized-sequence, two-way crossover study in healthy male Chinese volunteers

BACKGROUND

Risperidone is a benzisoxazole derivate and is effective in the treatment of schizophrenia and other psychiatric illnesses in adults and children. Although there are a few reports in the literature regarding the pharmacokinetic characteristics of risperidone, insufficient data on its pharmacokinetic properties in a Chinese population are available.

OBJECTIVE

To meet the requirements for marketing a new generic product, this study was designed to compare the pharmacokinetic properties and bioequivalence of two 2 mg tablet formulations of risperidone: a newly developed generic formulation (test) and a branded formulation (reference) in healthy adult male Chinese volunteers.

METHODS

A single-dose, open-label, randomized-sequence, 2 × 2 crossover study was conducted in fasted healthy male Chinese volunteers. Eligible participants were randomly assigned in a 1:1 ratio to receive 1 tablet (2 mg each) of the test formulation (Risperidone tablet; Dr. Reddy's Laboratories Ltd., Hyderabad, India) or the reference formulation (Risperdal(®) tablet; Xian-Janssen Pharmaceutical Ltd., Xi-an, China), followed by a 2-week washout period and subsequent administration of the alternate formulation. The study drugs were administered after a 10-hour overnight fast. Plasma samples were collected over 96 hours. Plasma concentrations of the parent drug, risperidone, and its active metabolite, 9-hydroxy-risperidone, were analyzed by a liquid chromatography-tandem mass spectrometry method. The formulations would be considered bioequivalent if the 90% confidence intervals (CIs) of the natural log-transformed values were within the predetermined 80-125% equivalence range for the maximum plasma drug concentration (Cmax) and the area under the plasma concentration-time curve (AUC), in accordance with guidelines issued by the US Food and Drug Administration. Assessment of tolerability was based on recording of adverse events (AEs), monitoring of vital signs, electrocardiograms, and laboratory tests at baseline and at completion of the study.

RESULTS

A total of 24 healthy male Chinese volunteers (mean age 22.9 years [standard deviation (SD) 2.7, range 19.2-27.1]; weight 63.2 kg [SD 7.0, range 52.0-78.0]; and height 171.3 cm [SD 6.1, range 162.0-187.0]) were enrolled, and all completed the study. For the parent drug, risperidone, the 90% CIs of the relative values (test vs. reference) of the Cmax, AUC from time zero to time t (AUCt), and AUC from time zero to infinity (AUC∞) were 97.0-124.0%, 92.7-115.1%, and 92.8-114.2%, respectively. For the active metabolite, 9-hydroxy-risperidone, the values were 104.4-117.7%, 101.0-113.7%, and 100.4-113.4%, respectively. The two formulations met the predetermined criteria for bioequivalence. A total of 73 AEs were observed in 24 subjects during the study. The most common AE was sedation (48 events), followed by nasal reactions (14 events), postural hypotension (3 events), hypertriglyceridemia (2 events), dizziness (4 events), nausea (1 event), and anorexia (1 event). Their severity was as follows: 16 were mild, 57 were moderate, and none were severe. The majority of the AEs were considered to be related (48 events) or probably related (23 events) to the study medication. No clinically significant abnormalities on physical examination, vital sign measurements, or electrocardiographic recordings were reported. No serious AEs were reported.

CONCLUSIONS

The data from this study in healthy adult male Chinese subjects suggest that the test formulation met the regulatory criteria for bioequivalence to the reference formulation, on the basis of the rate and extent of absorption. Both formulations were well tolerated.

Individualizing clozapine and risperidone treatment for schizophrenia patients

Schizophrenia is a severe disorder that significantly affects the quality of life and total functioning of patients and their caregivers. Clozapine is the first atypical antipsychotic with fewer adverse effects and established efficacy. As a rule of thumb, risperidone is one of the most reliable and effective antipsychotics for newly diagnosed and chronic schizophrenics. Pharmacogenetic studies have identified genomic variants of candidate genes that seem to be important in the way a patient responds to treatment. The recent progress made in pharmacogenomics will improve the quality of treatment, since drug doses will be tailored to the special needs of each patient. In this article, we review the available literature attempting to delineate the role of genomic variations in clozapine and risperidone response in schizophrenic patients of various ethnicities. We conclude that pharmacogenomics for these two drugs is still not ready for implementation in the clinic.

Pharmacological and clinical profile of recently approved second-generation antipsychotics: implications for treatment of schizophrenia in older patients

Antipsychotics are frequently used in elderly patients to treat a variety of conditions, including schizophrenia. While extensively studied for their impact in younger populations, there is comparatively limited evidence about the effectiveness of these agents in older patients. Further complicating this situation are the high comorbidity rates (both psychiatric and medical) in the elderly; age-related changes in pharmacokinetics that lead to a heightened proclivity for adverse effects; and the potential for multiple, clinically relevant drug interactions. With this background in mind, we review diagnostic and treatment-related issues specific to elderly patients suffering from schizophrenia. We then focus on the potential role of the most recently approved second-generation antipsychotics, paliperidone (both the extended-release oral formulation and the long-acting injectable formulation), iloperidone, asenapine and lurasidone, given the limited clinical experience with these agents in the elderly. While there is limited data to support their safety, tolerability and efficacy in older patients with schizophrenia, each has unique characteristics that should be considered when used in this population.

Developing in vitro-in vivo correlation of risperidone immediate release tablet

The present study was aimed to predict the absorption profile of a risperidone immediate release tablet (IR) and to develop the level A in vitro-in vivo correlation (IVIVC) of the drug using the gastrointestinal simulation based on the advanced compartmental absorption and transit model implemented in GastroPlus™. Plasma concentration data, physicochemical, and pharmacokinetic properties of the drug were used in building its absorption profile in the gastrointestinal tract. Since the fraction absorbed of risperidone in simulation was more than 90% with low water solubility, the drug met the criteria of class II of the Biopharmaceutics Classification System. The IVIVC was developed based on the model built using the plasma data and the in vitro dissolution data in several dissolution media based on the Japanese Guideline for Bioequivalence Studies of Generic Products. The gastrointestinal absorption profile of risperidone was successfully predicted. A level A IVIVC was also successfully developed in all dissolution media with percent prediction error for Cmax and the area under the curve less than 10% for both reference and test drug.

Risperidone inhibits contractions induced by serotonin and histamine and reduces K+ currents in smooth muscle of human umbilical artery

Risperidone is an antipsychotic commonly used during pregnancy. Because it can cross the placental barrier, our objective was to evaluate its actions on the smooth muscle of the human umbilical artery (HUA). Risperidone preincubation (1-300 nmol/L for 20 minutes) produced a significant decrease in maximum force development induced by serotonin or histamine in HUA rings. When applied on top of stable contractions induced by these agonists risperidone produced quick relaxations (IC(50) = 1 nmol/L for serotonin and 72 nmol/L for histamine). Risperidone induced the contraction of vascular rings depolarized by 40 mmol/L extracellular K(+) but not in the case of 80 mmol/L K(+), suggesting inhibition of K(+) channels. The patch-clamp technique showed that risperidone (3 nmol/L) inhibited whole-cell K(+) currents in freshly isolated HUA smooth muscle cells. Our results are the first showing risperidone effects in human vascular smooth muscle and highlight that its use during pregnancy should be adequately monitored.

Impact of CYP2D6 genotype on steady-state serum concentrations of risperidone and 9-hydroxyrisperidone in patients using long-acting injectable risperidone

An increased risk of adverse effects and discontinuation of risperidone therapy is observed in patients with impaired cytochrome P450 2D6 (CYP2D6) function on oral risperidone therapy. The present study is the first to investigate the impact of CYP2D6 genotype on serum concentrations of risperidone and 9-hydroxyrisperidone in patients using injectable long-acting risperidone. Two hundred three patients were divided into groups according to administered risperidone formulation (long-acting injection; n = 90) and CYP2D6 genotype. Dose-adjusted serum concentrations were compared using the CYP2D6*1/*1 subgroup as reference. The total serum concentration of risperidone plus 9-hydroxyrisperidone was 80% (P < 0.03) and 32% (P < 0.03) higher, whereas the risperidone-9-hydroxyrisperidone ratios were 6.3-fold (P < 0.01) and 12.5-fold (P < 0.01) higher in the CYP2D6def/def (def means defective allele, ie, CYP2D6*3, *4, *5, or *6) subgroup for long-acting and oral risperidone, respectively. In conclusion, CYP2D6 genotype significantly affects the pharmacokinetics of both oral and long-acting risperidone formulations.

PLGA nanoparticle formulations of risperidone: preparation and neuropharmacological evaluation

The aim of this work was to develop extended-release poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles of risperidone and thermal-responsive in situ gel containing risperidone nanoparticles for parenteral (subcutaneous) delivery and to reduce the dose-dependent extrapyramidal side effects of risperidone. PLGA nanoparticles of risperidone were designed by nanoprecipitation method using polymeric stabilizer (Poloxamer 407). The prepared nanoparticles were characterized for particle size by photon correlation spectroscopy and atomic force microscopy. Poloxamer 407-based in situ gel containing PLGA nanoparticles of risperidone was prepared by modified cold method to control the initial rapid release from the nanoparticles. The in vivo efficacy (antipsychotic effect) of prepared formulations (nanoparticles and in situ gel containing nanoparticles) was studied by administering them subcutaneously to mice. Extrapyramidal side effects of the formulations were also studied. The particle size of the prepared nanoparticles ranged between 85 and 219 nm. About 89% to 95% drug encapsulation efficiency was achieved when risperidone was loaded at 1.7% to 8.3% by weight of the polymer. During in vivo studies prepared risperidone formulations showed an antipsychotic effect that was significantly prolonged over that of risperidone solution for up to 72 hours with fewer extrapyramidal side effects. The prolonged effect of risperidone was obtained from the risperidone formulations administered subcutaneously, and this may improve the treatment of psychotic disorders by dose reduction.

FROM THE CLINICAL EDITOR

The development of extended-release poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles of risperidone is reported in this paper, along with the development of thermal-responsive in situ gel containing risperidone nanoparticles for parenteral (subcutaneous) delivery and to reduce the dose-dependent extrapyramidal side effects. In vivo studies showed a significantly prolonged antipsychotic effect with fewer extrapyramidal side effects.

Neuroprotective effect of atypical antipsychotics in cognitive and non-cognitive behavioral impairment in animal models

Antipsychotic drugs are divided into two groups: typical and atypical. Recent clinical studies show atypical antipsychotics have advantages over typical antipsychotics in a wide variety of neuropsychiatric conditions, in terms of greater efficacy for positive and negative symptoms, beneficial effects on cognitive functioning, and fewer extra pyramidal side effects in treating schizophrenia. As such, atypical antipsychotics may be effective in the treatment of depressive symptoms associated with psychotic and mood disorders, posttraumatic stress disorder and psychosis in Alzheimer disease. In this paper, we describe the effects and potential neurochemical mechanisms of action of atypical antipsychotics in several animal models showing memory impairments and/or non-cognitive behavioral changes. The data provide new insights into the mechanisms of action of atypical antipsychotics that may broaden their clinical applications.

Course, prognosis, and management of psychosis in Parkinson's disease: are current treatments really effective?

It is essential to recognize and treat psychosis in Parkinson's disease for several reasons. Studies have shown that psychosis in Parkinson's disease patients is a strong risk factor for nursing home placement. Psychosis may be the greatest source of stress for caretakers of Parkinson's patients; it is often persistent, and its presence markedly increases mortality. Treatment of psychotic symptoms should occur only after potential medical and environmental causes of delirium have been eliminated or addressed. Initial pharmacologic changes should include limiting the patient's antiparkinsonian medications to those that are necessary to preserve motor function. Should that fail, an atypical antipsychotic is presently the treatment of choice. An emerging treatment option is acetylcholinesterase inhibitors. This article reviews what is currently known about the course, prognosis, and treatment strategies in Parkinson's disease psychosis.

In vivo evaluation of risperidone-SAIB in situ system as a sustained release delivery system in rats

The objective of this study was to evaluate a sustained release sucrose acetate isobutyrate (SAIB) in situ system formulation of risperidone (RSP) in vivo. The formulation contained SAIB, ethanol, and polylactic acid (PLA) as a release regulator. In vivo pharmacokinetics (PK) studies have shown that PLA is effective in reducing the burst effect. After a 12.5mg/kg IM injection of a 25mg/g RSP-SAIB in situ system, the C(max) was markedly reduced from 944.1+/-80.2 to 330.4+/-33.6ng/ml by increasing PLA from 1% to 10% (w/w), the T(max) were prolonged from 2 to 4.3+/-2.0h, and the area under the curve from day 0 to 2 (AUC(0-2day)) was reduced significantly from 16294.8+/-3946.4 to 7025.3+/-1979.2ngh/ml. For the RSP-SAIB in situ system including 10% PLA, the high release rates over a short period allowed therapeutic plasma concentrations to be achieved in the initial stages after activation, and sustained release of the drug led to a stable plasma concentration (by day 25, the plasma concentration was 8% of the C(max)). These initial in vivo studies suggest that RSP-SAIB in situ system is effective as a sustained delivery system.

Pathophysiology and treatment of psychosis in Parkinson's disease: a review

Psychotic symptoms in Parkinson's disease (PD) are relatively common and, in addition to creating a disturbance in patients' daily lives, have consistently been shown to be associated with poor outcome. Our understanding of the pathophysiology of psychosis in PD has expanded dramatically over the past 15 years, from an initial interpretation of symptoms as dopaminergic drug adverse effects to the current view of a complex interplay of extrinsic and disease-related factors.PD psychosis has unique clinical features, namely that it arises within a context of a clear sensorium and retained insight, there is relative prominence of visual hallucinations and progression occurs over time. PD psychosis tends to emerge later in the disease course, and disease duration represents one risk factor for its development. The use of anti-PD medications (particularly dopamine receptor agonists) has been the most widely identified risk factor for PD psychosis. Other risk factors discussed in the literature include older age, disease severity, sleep disturbance, cognitive impairment, dementia and/or depression.Recent efforts have aimed to explore the complex pathophysiology of PD psychosis, which is now known to involve an interaction between extrinsic, drug-related and intrinsic, disease-related components. The most important extrinsic factor is use of dopaminergic medication, which plays a prominent role in PD psychosis. Intrinsic factors include visual processing deficits (e.g. lower visual acuity, colour and contrast recognition deficits, ocular pathology and functional brain abnormalities identified amongst hallucinating PD patients); sleep dysregulation (e.g. sleep fragmentation and altered dream phenomena); neurochemical (dopamine, serotonin, acetylcholine, etc.) and structural abnormalities involving site-specific Lewy body deposition; and genetics (e.g. apolipoprotein E epsilon4 allele and tau H1H1 genotype). Preliminary reports have also shown a potential relationship between deep brain stimulation surgery and PD psychosis.When reduction in anti-PD medications to the lowest tolerated dose does not improve psychosis, further intervention may be warranted. Several atypical antipsychotic agents (i.e. clozapine, olanzapine) have been shown to be efficacious in reducing psychotic symptoms in PD; however, use of clozapine requires cumbersome monitoring and olanzapine leads to motor worsening. Studies of ziprasidone and aripiprazole are limited to open-label trials and case reports and are highly variable; however, it appears that while each may be effective in some patients, both are associated with adverse effects. While quetiapine has not been determined efficacious in two randomized controlled trials, it is a common first-line treatment for PD psychosis because of its tolerability, ease of use and demonstrated utility in numerous open-label reports. Cholinesterase inhibitors currently represent the most promising pharmacological alternative to antipsychotics. Tacrine is rarely tried because of hepatic toxicity, and controlled trials with donepezil have not shown significant reductions in psychotic symptoms, due perhaps to methodological limitations. However, results from an open-label study and a double-blind, placebo-controlled trial involving 188 hallucinating PD patients support the efficacy of rivastigmine. With regard to non-pharmacological interventions, case reports suggest that electroconvulsive therapy has the potential to reduce psychotic symptoms and may be considered in cases involving concurrent depression and/or medication-refractory psychosis. Limited case reports also suggest that specific antidepressants (i.e. clomipramine and citalopram) may improve psychosis in depressed patients. Finally, studies in the schizophrenia literature indicate that psychological approaches are effective in psychosis management but, to date, this strategy has been supported only qualitatively in PD, and further studies are warranted.

Five-year follow-up during antipsychotic treatment: efficacy, safety, functional and social outcome

OBJECTIVE

Explore the long-term course of schizophrenia and related disorders.

METHOD

Naturalistic study of 225 patients initially treated with risperidone (monotherapy or in combination with other psychotropic drugs) over 5 years.

RESULTS

Stable symptomatology and side effects were observed. Clinician GAF scores were 55-61, but patients' self-ratings were higher. Clinician and patient CGI scores were at the same level. Annual in-patient days decreased but days in sheltered accommodations increased still more. Only 12% of the patients studied or worked full-time. One in four had no social contacts except with staff. Eight patients died during the 5 years.

CONCLUSION

The findings underline the chronicity and seriousness of psychotic disorders in terms of social outcome and, indirectly, the low quality of life of this group of persons. Patients were generally well aware of their illness and able to sort out symptoms from drug side effects. This opens for more active involvement of patients in monitoring their own treatment.