Delia Bishara

Upcoming agents for the treatment of schizophrenia: mechanism of action, efficacy and tolerability.

Since the introduction of a group of atypical antipsychotics in the 1990s, there has been a decline in the rate of new antipsychotics being introduced into clinical practice. However, with increasing safety and efficacy concerns over currently available drugs and a dearth of options available for atypical depot formulations, there is a considerable need for the development of new formulations and agents. This review examines the profile of seven antipsychotic drugs currently in the premarketing stage of development and summarizes their mechanism of action, clinical potential and safety.Asenapine is an antipsychotic with activity for multiple receptors and has potential to improve negative and cognitive symptoms of schizophrenia. Bifeprunox is a partial dopamine D2 and serotonin 5-HT1A receptor agonist showing a less than convincing efficacy profile, but which may offer safety advantages over available agents by means of a reduced risk of metabolic complications. Iloperidone is a D2 and 5-HT2A receptor antagonist requiring further studies to establish its effectiveness. It has a high affinity for α1-adrenoceptors, which can lead to associated haemodynamic adverse effects. Nemonapride is essentially a typical antipsychotic drug, similar in structure to sulpiride, which has been available for some time in Japan. It has efficacy against positive symptoms and has shown some antidepressant and anxiolytic properties, although efficacy data for it are somewhat limited. Norclozapine (N-desmethylclozapine) is a major metabolite of clozapine formed by its demethylation. Its partial agonist activity at D2 receptors has raised interest in it as an antipsychotic in its own right. In addition, it appears to have muscarinic agonist activity, which is believed to be responsible for the observed positive effects it has on cognition. It was envisaged to be effective as an adjunct to other agents or at high doses in the treatment of refractory schizophrenia, although a recent randomized, controlled study showed that it was no more effective than placebo in patients with schizophrenia experiencing an acute psychotic episode. Olanzapine pamoate depot injection has shown comparable efficacy to oral olanzapine in several studies. However, it has provoked considerable safety concerns by its association with inadvertent intravascular injection events in numerous patients. This accidental intravascular administration of olanzapine pamoate leads to excessive sedation, confusion, dizziness and altered speech. Post-injection observation periods and postmarketing surveillance are planned following the introduction of the depot. Paliperidone palmitate is the palmitate ester of paliperidone, the major metabolite of risperidone, and is formulated as a long-acting injection for intramuscular use. Its pharmacology is comparable to risperidone, having D2 and 5-HT2A receptor antagonist activity. Efficacy studies have shown positive results, and because paliperidone has no antagonistic activity at cholinergic receptors, it has low potential for anticholinergic adverse effects, including cognitive dysfunction. However, with higher doses, the frequency of extrapyramidal side effects and orthostatic hypotension have been shown to be greater than with placebo.

Once-monthly paliperidone injection for the treatment of schizophrenia

Paliperidone palmitate is a new long-acting antipsychotic injection for the treatment of acute and maintenance therapy in schizophrenia. Paliperidone (9-hydroxyrisperidone) is the major active metabolite of risperidone and acts at dopamine D2 and serotonin 5HT2A receptors. As with other atypical antipsychotics, it exhibits a high 5HT2A:D2 affinity ratio. It also has binding activity as an antagonist at α1-and α2 adrenergic receptors and H1 histaminergic receptors, but has virtually no affinity for cholinergic receptors. Paliperidone palmitate has been shown to be effective in reducing Positive and Negative Syndrome Scale total scores in four short-term trials in acute schizophrenia. It was also effective as maintenance therapy in a long-term trial in which time to recurrence of symptoms was significantly longer in paliperidone-treated patients compared with placebo. In addition, paliperidone was shown to be noninferior to risperidone long-acting injection in one study, but this noninferiority was not established in another longer study comparing the two drugs. Treatment should be initiated with 234 mg on day 1 and 156 mg on day 8, followed by a recommended monthly maintenance dose of 39–234 mg based on efficacy and tolerability. Paliperidone palmitate is generally well tolerated, although it can cause weight gain and a rise in prolactin levels, which is generally greater in women than in men. Overall, paliperidone palmitate may have advantages over other currently available long-acting injections, and therefore may be a useful alternative for the treatment of schizophrenia, although further long-term trials comparing it with active treatments are warranted.

Clozapine-related EEG changes and seizures: dose and plasma-level relationships

Clozapine is a widely used atypical antipsychotic with a unique effectiveness in treatment-resistant schizophrenia. An important adverse effect is seizures, which have been observed at all stages of clozapine treatment. Valproate has traditionally been considered the drug of choice for the prophylaxis of clozapine seizures, however it may not be the most suitable choice for all patients. There is disagreement as to the best point to prescribe valproate or a suitable antiepileptic: as seizure prophylaxis at a certain clozapine dose or level, or only as remedial treatment. In this review, we examine the relevant literature with an aim to evaluate the following relationships: clozapine dose and electroencephalogram (EEG) abnormalities, plasma levels and EEG abnormalities, dose and occurrence of seizures and plasma levels and occurrence of seizures. Weighted linear regression models were fitted to investigate these relationships. There was a strong relationship between clozapine dose and plasma level and occurrence of clozapine-induced EEG abnormalities. However, a statistically significant relationship between dose and occurrence of seizures was not found. A relationship between clozapine plasma level and occurrence of seizures was not established because of the scarcity of useful data although our review found three case reports which suggested that there is a very substantial risk of seizures with clozapine plasma levels exceeding 1300  µg/l. Seizures are more common during the initiation phase of clozapine treatment, suggesting a slow titration to target plasma levels is desirable. An antiepileptic drug should be considered when the clozapine plasma level exceeds 500  µg/l, if the EEG shows clear epileptiform discharges, if seizures, myoclonic jerks or speech difficulties occur and when there is concurrent use of epileptogenic medication. The antiepileptics of choice for the treatment and prophylaxis of clozapine-induced seizures are valproate (particularly where there is mood disturbance) and lamotrigine (where there is resistance to clozapine).

Asenapine monotherapy in the acute treatment of both schizophrenia and bipolar I disorder

Asenapine is a new atypical antipsychotic agent currently under development for the treatment of schizophrenia and bipolar disorder. It has high affinity for various receptors including antagonism at 5HT2A, 5HT2B, 5HT2C, 5HT6 and 5HT7 serotonergic receptor subtypes, α1A, α2A, α2B and α2C adrenergic and D3 and D4 dopaminergic receptors. As with other atypicals, asenapine exhibits a high 5HT2A:D2 affinity ratio. Although similar to clozapine in its multi-target profile, it shows no appreciable affinity for muscarinic receptors. Asenapine has shown efficacy in alleviating both positive and negative symptoms of schizophrenia compared with placebo. Although promising, further studies are required in order to determine whether it has advantages over placebo and other antipsychotics in alleviating cognitive impairment associated with schizophrenia. It has also shown long-term efficacy comparable with olanzapine in bipolar I disorder. Asenapine is generally well tolerated and appears to be metabolically neutral. It has low propensity to cause weight gain and prolactin elevation. There were no concerns in the studies about its effects on the cardiovascular system and QTc prolongation. The incidence of extrapyramidal symptoms with asenapine however has been found to be higher than that with olanzapine. It may be a useful alternative to aripiprazole in schizophrenia and bipolar disorder in patients who are at high risk of metabolic abnormalities.

Risperidone long-acting injection: a 6-year mirror-image study of healthcare resource use

Objective:  To evaluate naturalistic use of risperidone long‐acting injection (RLAI) and its effect on healthcare resource use.

Olanzapine: A systematic review and meta-regression of the relationships between dose, plasma concentration, receptor occupancy and response

ObjectiveTo conduct a systematic review examining the relationships between olanzapine dose, clinical outcome, dopamine occupancy, and plasma concentration; and to evaluate the potential for therapeutic drug monitoring. MethodsA search using Embase, Medline, and Pubmed was conducted; and the literature was systematically reviewed. Studies meeting inclusion criteria were examined. The relationships between olanzapine dose, response, dopamine occupancy, and concentration were analyzed using statistical regression. ResultsTen studies were included in the analysis for dose-response. The effect size–dose relationship showed a typical dose-response curve with minimal rise in slope for doses higher than 10 mg/d. For the dose-occupancy relationship, 6 studies were included. Doses more than approximately 12 mg/d were sufficient to block 65% of striatal D2 receptors. Doses higher than 20 mg led to minimally higher receptor occupancies. Fifteen studies were included in the meta-regression of olanzapine mean concentrations. A linear relationship between mean plasma concentration and mean dose was observed. ConclusionsOur review suggests that the likelihood of a favorable response with olanzapine is maximized at doses of 10 to 15 mg/d (perhaps lower in nonsmoking females). Higher doses may be considered if 15 mg is ineffective and if plasma level is less than 20 ng/mL on that dose. There is a direct linear relationship between olanzapine dose and plasma concentration. Therapeutic drug monitoring may be useful in patients who are suspected of nonadherence, where there is potential for a drug interaction, and in patients taking 15 mg/d or more and who have not reached clinical response.

Quality of prescribing for schizophrenia: Evidence from a national audit in England and Wales

The National Audit of Schizophrenia (NAS) examined the quality of care received in England and Wales. Part of the audit set out to determine whether six prescribing standards, set by the national clinical guidelines for schizophrenia, were being implemented and to prompt improvements in care. Mental Health Trusts and Health Boards provided data obtained from case-notes for adult patients living in the community with schizophrenia or schizoaffective disorder. An audit of practice tool was developed for data collection. Most of the 5055 patients reviewed were receiving pharmacological treatment according to national guidelines. However, 15.9% of the total sample (95%CI: 14.9-16.9) were prescribed two or more antipsychotics concurrently and 10.1% of patients (95%CI: 9.3-10.9) were prescribed medication in excess of recommended limits. Overall 23.7% (95%CI: 22.5-24.8) of patients were receiving clozapine. However, there were many with treatment resistance who had no clear reason documented as to why they had not had a trial of clozapine (430/1073, 40.1%). In conclusion, whilst most people were prescribed medication in accordance with nationally agreed standards, there was considerable variation between service providers. Antipsychotic polypharmacy, high dose prescribing and clozapine underutilisation in treatment resistance were all key concerns which need to be further addressed.

Expert opinion on the management of behavioural and psychological symptoms of dementia (BPSD) and investigation into prescribing practices in the UK

The management of Behavioural and Psychological Symptoms of Dementia (BPSD) has been the subject of considerable debate over the last few years in view of the poor evidence base for pharmacological agents and concerns about their safety.

Adverse Effects of Clozapine in Older Patients: Epidemiology, Prevention and Management

Research into the use of clozapine in older people is somewhat scarce. Clozapine is associated with serious adverse effects such as agranulocytosis, seizures, myocarditis and metabolic syndrome. Other common undesirable effects such as sedation, constipation (which can be fatal), urinary incontinence and hypersalivation further limit its use. These adverse effects are particularly important for the use of clozapine in older people, who are generally more susceptible to medication-related adverse effects. Whilst clozapine should be used with caution in elderly people, strict monitoring procedures can help to prevent harmful effects through early detection, and certain management techniques exist to minimise them. This review outlines the epidemiology of clozapine-related adverse effects in older people and discusses potential prevention and management strategies.

Anticholinergic effect on cognition (AEC) of drugs commonly used in older people

Use of anticholinergic drugs in older people is associated with increased risk of cognitive decline and of dementia and death.