Pathophysiology and management of risperidone-induced sialorrhea: case report

Background

Among antipsychotics, sialorrhea is most associated with clozapine, and when it occurs, it is uncomfortable, socially stigmatizing, and can contribute to medication non-adherence. Risperidone has a generally negligible muscarinic activity compared to clozapine, and yet, multiple reports of severe sialorrhea associated with risperidone have been reported.

Case presentation

This case report describes risperidone-induced sialorrhea that was unintentionally masked by simultaneous clonidine administration that was intended to treat hypertension. Interestingly, sialorrhea was present but mild when clonidine was present; however, when risperidone was further titrated and clonidine removed, a significant worsening of sialorrhea developed. Sialorrhea did not respond to treatment with anticholinergic medication.

Conclusion

The pathophysiology of antipsychotic-induced sialorrhea is complex and varies between antipsychotics. Risperidone-induced sialorrhea is suspected of having prominent adrenergic pathophysiology that is likely composed of highly viscoelastic saliva (high protein content), differing from the more commonly encountered clozapine-induced sialorrhea. Risperidone-induced sialorrhea is reported as more likely to respond to dose reduction and treatment with α2-adrenergic receptor agonists or β-adrenergic receptor antagonists and less likely to respond to anticholinergic (antimuscarinic) medications.

Pharmacological agents selectively acting on the channel moieties of TRPM6 and TRPM7

The transient receptor potential cation channel, subfamily M, members 6 and 7 (TRPM6 and TRPM7) are homologous membrane proteins encompassing cation channel units fused to cytosolic serine/threonine-protein kinase domains. Clinical studies and experiments with animal disease models suggested that selective inhibition of TRPM6 and TRPM7 currents might be beneficial for subjects with immune and cardiovascular disorders, tumours and other pathologies, but the suitable pharmacological toolkit remains underdeveloped. The present study identified small synthetic molecules acting specifically on the channel moieties of TRPM6 and TRPM7. Using electrophysiological analysis in conjunction with Ca²⁺ imaging, we show that iloperidone and ifenprodil inhibit the channel activity of recombinant TRPM6 with IC₅₀ values of 0.73 and 3.33 µM, respectively, without an impact on the TRPM7 channel. We also found that VER155008 suppresses the TRPM7 channel with an IC₅₀ value of 0.11 µM but does not affect TRPM6. Finally, the effects of iloperidone and VER155008 were found to be suitable for blocking native endogenous TRPM6 and TRPM7 in a collection of mouse and human cell models. Hence, the identification of iloperidone, ifenprodil, and VER155008 allows for the first time to selectively manipulate TRPM6 and TRPM7 currents.

Long-Term Treatment with Atypical Antipsychotic Iloperidone Modulates Cytochrome P450 2D (CYP2D) Expression and Activity in the Liver and Brain via Different Mechanisms

CYP2D enzymes engage in the synthesis of endogenous neuroactive substances (dopamine, serotonin) and in the metabolism of neurosteroids. The present work investigates the effect of iloperidone on CYP2D enzyme expression and activity in rat brains and livers. Iloperidone exerted a weak direct inhibitory effect on CYP2D activity in vitro in the liver and brain microsomes (K_i = 11.5 μM and K_i = 462 μM, respectively). However, a two-week treatment with iloperidone (1 mg/kg ip.) produced a significant decrease in the activity of liver CYP2D, which correlated positively with the reduced CYP2D1, CYP2D2 and CYP2D4 protein and mRNA levels. Like in the liver, iloperidone reduced CYP2D activity and protein levels in the frontal cortex and cerebellum but enhanced these levels in the nucleus accumbens, striatum and substantia nigra. Chronic iloperidone did not change the brain CYP2D4 mRNA levels, except in the striatum, where they were significantly increased. In conclusion, by affecting CYP2D activity in the brain, iloperidone may modify its pharmacological effect, via influencing the rate of dopamine and serotonin synthesis or the metabolism of neurosteroids. By elevating the CYP2D expression/activity in the substantia nigra and striatum (i.e., in the dopaminergic nigrostriatal pathway), iloperidone may attenuate extrapyramidal symptoms, while by decreasing the CYP2D activity and metabolism of neurosteroiods in the frontal cortex and cerebellum, iloperidone can have beneficial effects in the treatment of schizophrenia. In the liver, pharmacokinetic interactions involving chronic iloperidone and CYP2D substrates are likely to occur.

The Effect of Chronic Iloperidone Treatment on Cytochrome P450 Expression and Activity in the Rat Liver: Involvement of Neuroendocrine Mechanisms

In order to achieve a desired therapeutic effect in schizophrenia patients and to maintain their mental wellbeing, pharmacological therapy needs to be continued for a long time, usually from the onset of symptoms and for the rest of the patients' lives. The aim of our present research is to find out the in vivo effect of chronic treatment with atypical neuroleptic iloperidone on the expression and activity of cytochrome P450 (CYP) in rat liver. Male Wistar rats received a once-daily intraperitoneal injection of iloperidone (1 mg/kg) for a period of two weeks. Twenty-four hours after the last dose, livers were excised to study cytochrome P450 expression (mRNA and protein) and activity, pituitaries were isolated to determine growth hormone-releasing hormone (GHRH), and blood was collected for measuring serum concentrations of hormones and interleukin. The results showed a broad spectrum of changes in the expression and activity of liver CYP enzymes, which are important for drug metabolism (CYP1A, CYP2B, CYP2C, and CYP3A) and xenobiotic toxicity (CYP2E1). Iloperidone decreased the expression and activity of CYP1A2, CP2B1/2, CYP2C11, and CYP3A1/2 enzymes but increased that of CYP2E1. The CYP2C6 enzyme remained unchanged. At the same time, the level of GHRH, GH, and corticosterone decreased while that of T₃ increased, with no changes in IL-2 and IL-6. The presented results indicate neuroendocrine regulation of the investigated CYP enzymes during chronic iloperidone treatment and suggest a possibility of pharmacokinetic/metabolic interactions produced by the neuroleptic during prolonged combined treatment with drugs that are substrates of iloperidone-affected CYP enzymes.

Sex-Specific Cannabidiol- and Iloperidone-Induced Neuronal Activity Changes in an In Vitro MAM Model System of Schizophrenia

Cortical circuit dysfunction is thought to be an underlying mechanism of schizophrenia (SZ) pathophysiology with normalization of aberrant circuit activity proposed as a biomarker for antipsychotic efficacy. Cannabidiol (CBD) shows potential as an adjunctive antipsychotic therapy; however, potential sex effects in these drug interactions remain unknown. In the present study, we sought to elucidate sex effects of CBD coadministration with the atypical antipsychotic iloperidone (ILO) on the activity of primary cortical neuron cultures derived from the rat methylazoxymethanol acetate (MAM) model used for the study of SZ. Spontaneous network activity measurements were obtained using a multielectrode array at baseline and following administration of CBD or ILO alone, or combined. At baseline, MAM male neurons displayed increased bursting activity whereas MAM female neurons exhibited no difference in bursting activity compared to sex-matched controls. CBD administered alone showed a rapid but transient increase in neuronal activity in the MAM networks, an effect more pronounced in females. Furthermore, ILO had an additive effect on CBD-induced elevations in activity in the MAM male neurons. In the MAM female neurons, CBD or ILO administration resulted in time-dependent elevations in neuronal activity, but the short-term CBD-induced increases in activity were lost when CBD and ILO were combined. Our findings indicate that CBD induces rapid increases in cortical neuronal activity, with sex-specific drug interactions upon ILO coadministration. This suggests that sex should be a consideration when implementing adjunct therapy for treatment of SZ.

Long-term effects of iloperidone on cerebral dopamine receptor subtypes

The atypical antipsychotic drug iloperidone has high affinity for a wide range of neurotransmitter receptors, including dopaminergic (DA), serotonergic, and adrenergic receptors. We examined the long-term effects of multiple doses of iloperidone on DA D1 , D2 , D3 , and D4 receptor subtypes. Sprague-Dawley adult rats (n = 8/group) received daily intraperitoneal injections of iloperiodone (0.5, 1, or 5 mg/kg) or vehicle for 4 weeks. Receptor autoradiography quantified the levels of DA receptors in medial prefrontal cortex (MPC), dorsolateral frontal cortex (DFC), caudate putamen (CPu), nucleus accumbens (NAc), and hippocampus (HIP). Four weeks of iloperidone treatment at 5 mg/kg significantly increased D1 receptors in NAc (36%) and CPu (38%). Iloperidone (1.5 and 5 mg/kg) dose-dependently increased D2 receptors in MPC (37 and 47%) and HIP (32 and 40%). Only the high dose of iloperidone (5 mg/kg) increased D2 receptors in NAc (39%) and CPu (38%). Repeated treatment with iloperidone (1.5 and 5 mg/kg) increased D4 receptors in the NAc (39 and 78%), CPu (42 and 83%) and HIP (54 and 72%). The three doses of iloperidone failed to alter D3 receptors in the brain regions examined in this study. These results suggest that iloperidone exerts region- and dose-specific effects on forebrain DA receptor subtypes, which may contribute to its therapeutic benefits in improving the positive and negative symptoms of schizophrenia with minimal extrapyramidal side effects.

Formulation and Characterization of Fast-Dissolving Sublingual Film of Iloperidone Using Box-Behnken Design for Enhancement of Oral Bioavailability

Iloperidone is a second-generation antipsychotic drug which is used for the treatment of schizophrenia and has very low aqueous solubility and bioavailability. This drug also undergoes first-pass metabolism. The aim of this work is to formulate fast-dissolving sublingual films of iloperidone to improve its bioavailability. Sublingual films were prepared by solvent casting method. Hydroxypropyl methyl cellulose E5, propylene glycol 400, and transcutol HP were optimized using Box-Behnken three-level statistical design on the basis of disintegration time and folding endurance of films. Iloperidone:hydroxypropyl-β-cyclodextrin kneaded complex was used in films instead of plain drug due to its low solubility. Optimized film was further evaluated for drug content, pH, dissolution studies, ex vivo permeation studies, and pharmacokinetic studies in rats. The optimized film disintegrated within 30 s. The in vitro dissolution of the film showed 80.3 ± 3.4% drug dissolved within first 5 min. In ex vivo permeation studies using sublingual tissue, flux achieved within first 15 min by film was around 117.1 ± 0.35 (mcg/cm²/h) which was ten times more than that of plain drug. This formulation showed excellent uniformity. AUC and C_max of film were significantly higher (p < 0.001) as compared to plain drug and relative bioavailability of the films was 148% when compared to the plain drug. Thus, this study showed optimized fast-dissolving sublingual film to improve permeation and bioavailability of iloperidone. Fast-dissolving films will be customer-friendly approach for geadiatric schizophrenic patients.

Graphic representation of pharmacology: Development of an alternative model

Introduction:

Providing clinicians with an easy to grasp and understandable representation of pharmacology is important to allow optimal clinical decisions to be made. Two of the most clinically relevant dimensions are receptor binding affinity and functional activity. The binding affinity for an agonist is described by the dissociation constant (K_A), and an antagonist by the inhibition constant (K_i). Functionally, medications can act as superagonists, agonists, partial agonists, antagonists, partial inverse agonists, or inverse agonists at several receptor sites, transporters, or ion channels. Comprehending the differences between agents is complicated by the number and types of binding sites.

Methods:

Binding and functional data are obtained from primary literature, product labels, human cloned receptor binding, and other sources. Binding affinities are converted into ratios relative to the putative primary receptor for that category of agent. Antipsychotic binding is referenced to dopamine type 2 long (D2L) receptor binding. Binding affinity ratios (BARs) generate a 6-spoked diagram, with D2L as the hub. The most avidly bound sites are the spokes, and the disk diameter represents the BAR. Where functional data are available, they are shown as a pie chart shading the binding site's disk.

Results:

Binding and function diagrams are shown for the antipsychotics where binding data are available and are compared to previous methods of pharmacologic comparisons of antipsychotics.

Discussion:

Use of graphic models of psychotropic pharmacology improves clinician comprehension and may serve as an aid to improve rational therapeutics and patient outcomes.

poison centers

CONTEXT

Asenapine, iloperidone and lurasidone are relatively new atypical antipsychotics. There is limited information on toxicity on pediatric exposures to these drugs. The objective of this study was to compare toxicity associated with asenapine, iloperidone and lurasidone exposures in young children.

METHODS

A retrospective study of U.S. National Poison Data System from 2010 to 2015 of single substance exposures to asenapine, iloperidone or lurasidone in children <6 years of age that were followed to known outcome was performed.

RESULTS

There were 95 asenapine, 64 iloperidone and 124 lurasidone cases that met inclusion criteria. Reason was exploratory for 96% of cases. Drowsiness/lethargy occurred most frequently with iloperidone (45%) and least often with lurasidone (8%). Two iloperidone cases had respiratory depression. For asenapine, iloperidone and lurasidone, respectively, management sites were on-site non-health care facility (non-HCF) (32%, 16%, 26%), treated/discharged from emergency department (ED) (46%, 47%, 63%), admitted to noncritical care (9%, 14%, 10%) and admitted to critical care (10%, 22%, 2%). Clinical effect duration was 8 h or less for the majority of non-HCF cases (80%) and for children treated/discharged from the ED (72%). For asenapine, iloperidone and lurasidone, coded outcomes were no effect (50%, 41%, 81%), minor effect (43%, 39%, 17%), moderate (6%, 19%, 2%) and major (0, 2%, 0).

DISCUSSION AND CONCLUSIONS

These findings suggest that in children under 6 years of age, lurasidone exposures were least serious and iloperidone exposures were most serious based on clinical effects, management sites and coded outcomes. Observation of symptomatic children in the ED for 8 h should be sufficient to make triage decisions based on persistence or resolution of clinical effects.

Iloperidone in the treatment of schizophrenia: an evidence-based review of its place in therapy

Introduction

Schizophrenia is a chronic and debilitating mental disorder that affects the patient’s and their family’s quality of life, as well as financial costs and health care settings. Despite the variety of available antipsychotics, optimal treatment outcomes are not always achieved. Novel drugs, such as iloperidone, can provide more effective, tolerable and safer strategies.

Aim

To review the evidence for the clinical impact of iloperidone on the treatment of patients with schizophrenia.

Evidence review

Clinical trials, observational studies and meta-analyses reached a common consensus that iloperidone is as effective as haloperidol, risperidone and ziprasidone in reducing schizophrenia symptoms. Similar amounts of adverse events and discontinuations were observed with iloperidone compared to placebo and active treatments. Common adverse events are mild and include dizziness, hypotension, dry mouth and weight gain. Iloperidone can induce extension of QTc interval, and clinicians should be aware of its contraindications. In long-term trials, iloperidone also showed promising safety and tolerability profiles. The low propensity to cause akathisia, extrapyramidal symptoms (EPS), increased prolactin levels or changes to metabolic laboratory parameters support its use in practice. Results showed that iloperidone prevents relapse in stabilized patients, with a time to relapse superior to placebo and similar to haloperidol. Patients using a prior antipsychotic (eg, risperidone and aripiprazole) can easily switch to iloperidone with no serious impact on safety or efficacy. However, the acquisition costs of iloperidone may hamper its use. Further evidence comparing iloperidone with other antipsychotics, and pharmacoeconomic studies would be welcome.

Place in therapy

Considering just the clinical profile of iloperidone, it represents a promising drug for treating schizophrenia, particularly in patients who are intolerant to previous antipsychotics, as well as being suitable as first-line therapy. Cost-effectiveness comparisons are needed to justify its use in clinical practice.

A placebo-controlled crossover study of iloperidone augmentation for residual anger and irritability in major depressive disorder

BACKGROUND

Even when patients experience remission with antidepressants, many continue to report anger attacks and excessive irritability despite continued treatment. Iloperidone antagonizes 5-HT-2a, D2, and alpha-1 receptors, which can have anti-aggressive effects. We examined iloperidone's safety and efficacy as an augmentation agent in outpatients with partially remitted major depressive disorder (MDD) with residual symptoms of anger and irritability.

METHODS

A total of 13 outpatients with partially remitted MDD [currently treated with selective serotonin reuptake inhibitors (SSRIs)] received four weeks of iloperidone or placebo, followed by one week of washout. Patients were then crossed over to the other treatment arm for 4 weeks. Treatment arms were randomized and double blind; and two sites were used for the study. Analyses compared treatment response using the Symptom Questionnaire (SQ) Anger/Hostility Subscale as the primary outcome measure.

RESULTS

There was no significant differential effect of iloperidone × weeks on the SQ Anger/Hostility Subscore over the course of the study, compared with placebo × weeks, regardless of administration order (p = 0.77).

CONCLUSIONS

Iloperidone did not significantly outperform placebo on measures of anger or irritability in patients with partially remitted MDD and residual anger/irritability.

Iloperidone-induced ejaculatory dysfunction: A case series

Disorders of ejaculation are the consequences of surgical procedures and with the use of various drugs. Until date, most drugs reported to induce ejaculatory dysfunctions such as retrograde ejaculation or dry orgasms share the capacity to significantly antagonize alpha 1-adrenergic receptor. Iloperidone, a new dopamine Type 2 and serotonin Type 2A antagonist similar to risperidone, provides better efficacy with lesser extra-pyramidal side effects. In addition, it also antagonize alpha 1-adrenergic receptor and alpha-2C receptors. Limited data is available for iloperidone-induced ejaculation dysfunction. This article features five schizophrenic patients which developed retrograde ejaculation during treatment with iloperidone. The ejaculatory dysfunction following treatment with iloperidone could be postulated due to blocking of alpha 1-adrenergic receptor.

Weight gain and antipsychotics: a drug safety review

INTRODUCTION

Second-generation antipsychotics (SGAs) are widely used in several psychiatric disease entities and exert to a different extent a risk for antipsychotic-induced weight gain (AIWG). As AIWG is associated with an increase in metabolic syndrome or cardiovascular events, knowledge of these risks is crucial for further monitoring and the initiation of counteractive measures.

AREAS COVERED

We searched PubMed and Web of Sciences for randomized-controlled trials and naturalistic observational studies published between 2010 and 2014 with sample sizes exceeding 100, including all marketed SGAs apart from zotepine, and providing data on weight increase. We also summarized relevant systematic reviews and meta-analyses of head-to-head comparisons.

EXPERT OPINION

Recently published data still support the hierarchical ranking of SGAs already proposed in previous reviews ranking clozapine and olanzapine as having the highest risk, followed by amisulpride, asenapine, iloperidone, paliperidone, quetiapine, risperidone and sertindole in the middle, and aripiprazole, lurasidone and ziprasidone with the lowest risk. Number needed to harm varied considerably in our meta-analysis. Younger patients and patients with a lower baseline body mass index are most vulnerable. The greatest amount of weight gain occurs within the first weeks of treatment. AIWG occurs in all diagnostic groups and is also common in treatment with first-generation antipsychotics; therefore, awareness of this adverse event is essential for anyone prescribing antipsychotics.

Rationale for iloperidone in the treatment of posttraumatic stress disorder

Multiple controlled efficacy studies are available to support the use of psychotropic medications in the treatment of posttraumatic stress disorder symptoms. Iloperidone, a recently approved atypical antipsychotic, has yet to be evaluated in such a manner. This unique agent has the highest affinity of all antipsychotics toward alpha-1 receptors. Antagonism of central nervous system alpha-1 receptors has been implicated in certain aspects of posttraumatic stress disorder, as evidenced by the beneficial role of prazosin in treating nightmares. Additional reduction in hypervigilance may occur through blockade of dopamine receptor D2 and serotonin receptors in the 5-HT2 family. Further investigation of iloperidone is warranted in the treatment of patients with posttraumatic stress disorder due to its unique receptor binding profile.

Long-term efficacy and safety of iloperidone: an update

Schizophrenia is a devastating neuropsychiatric disease with a worldwide prevalence of approximately 0.5%-1%. Since many patients do not achieve adequate symptom relief from available agents, alternate pharmacotherapeutic approaches are needed. In this context, iloperidone was recently approved by the US Food and Drug Administration for the treatment of schizophrenia. This paper first reviews its pharmacodynamic and pharmacokinetic profiles, emphasizing their clinical relevance. Next, it summarizes the literature on its acute and maintenance efficacy, safety, and tolerability. It then considers pharmacogenetic data which may help to predict response and risk of cardiac arrhythmias with this agent. Finally, it critically positions iloperidone relative to other first- and second-generation antipsychotics.

Ventricular premature contractions associated with iloperidone

Typical and atypical antipsychotic drugs are known to block potassium repolarization channels, prolong the QTc interval, and thereby predispose to ventricular tachyarrhythmias. We report a young male schizophrenic patient who experienced clinically significant and symptomatically distressing ventricular premature contractions (VPCs) in close temporal relation with iloperidone (8-16 mg/day) treatment; there had been no VPCs with prior exposure to risperidone, trihexyphenidyl, and olanzapine, nor with subsequent exposure to asenapine. We hypothesize that the VPCs may have been triggered by an alpha 2c receptor blockade-mediated cardiostimulatory action associated with iloperidone.

Iloperidone-induced Galactorrhea in a Middle-aged Female

Iloperidone, a piperidinyl-benzisoxazole derivative, is structurally related to risperidone and approved for treatment in acute stage of schizophrenia. Iloperidone is usually considered as a prolactin sparing atypical antipsychotic thereby offering treatment advantage. We aim to present the first reported case of iloperidone-induced hyperprolactinemic galactorrhea in a middle-aged female. A middle-aged female with the diagnosis of paranoid schizophrenia was treated with iloperidone up to a dosage of 8 mg/day. Three months after starting the medicine, patient developed galactorrhea for which no other medical cause could be ascertained except for increased prolactin level. Iloperidone was stopped and aripiprazole was initiated with which galactorrhea subsided and prolactin level returned to normal. Index case report amply demonstrates that Iloperidone can cause hyperprolactinemic galactorrhea even at low dosage and after considerable period into the treatment.

A review of new atypical antipsychotic launches in the United States

In this article we investigate the post-launch retail prescription trends of asenapine (Saphris(®), Merck and Co.) and iloperidone (Fanapt(®), Vanda Pharmaceuticals Inc./Novartis), two new atypical antipsychotics to launch in the United States market in October 2009 and January 2010, respectively. In the first 12 months following the asenapine launch, and in the nine months since the iloperidone launch, asenapine and iloperidone have secured 0.22 and 0.10 percent of the total prescription market; however, both products nearly double those respective shares when total prescriptions are isolated to new patient prescriptions (0.44% for asenapine and 0.17% for iloperidone). Since launch, asenapine has shown stronger signs of growth, largely attributed to its approval in multiple indications as compared to iloperidone's single indication.

New atypical antipsychotics for schizophrenia: iloperidone

The optimal treatment of schizophrenia poses a challenge to develop more effective treatments and safer drugs, to overcome poor compliance, discontinuation and frequent switching with available antipsychotics. Iloperidone is a new dopamine type 2/serotonin type 2A (D(2)/5-HT(2A)) antagonist structurally related to risperidone, expected to give better efficacy with less extrapyramidal symptoms than D(2) receptor antagonist antipsychotics. In double-blind phase III trials iloperidone reduced the symptoms of schizophrenia at oral doses from 12 to 24 mg. It was more effective than placebo in reducing positive and negative syndrome total score and Brief Psychiatric Rating scale scores; it was as effective as haloperidol and risperidone in post-hoc analysis. Its long-term efficacy was equivalent to that of haloperidol. The most common adverse events were dizziness, dry mouth, dyspepsia and somnolence, with few extrapyramidal symptoms and metabolic changes in short- and long-term studies in adults. Akathisia was rare, but prolongation of the corrected QT (QTc) interval was comparable to haloperidol and ziprasidone, which is of particular concern. Further comparative studies are needed to clarify the benefit/risk profile of iloperidone and its role in the treatment of schizophrenia.