Effect of combined treatment with aripiprazole and antidepressants on the MK-801-induced deficits in recognition memory in novel recognition test and on the release of monoamines in the rat frontal cortex

According to preclinical and clinical studies, the antidepressant-induced increase in the activity of atypical antipsychotics may efficiently improve the treatment of negative and some cognitive symptoms of schizophrenia. In the present study, we aimed to evaluate the effects of the antidepressants escitalopram and mirtazapine and the atypical antipsychotic drug aripiprazole, administered separately or in combination, on the MK-801-induced deficits in the recognition memory test and on the extracellular levels of monoamines and their metabolites in the rat frontal cortex. Based on the results of the behavioral tests, co-treatment with an ineffective dose of aripiprazole (0.1 mg/kg) and escitalopram (2.5 and 5 mg/kg) or mirtazapine (5 mg/kg) abolished the deficits evoked by MK-801 in the novel object recognition test, and those effects were blocked by the 5-HT_1A receptor antagonist (WAY 100,635) or the dopamine D₁ receptor antagonist (SCH 23,390). Moreover, co-treatment with aripiprazole (0.3 mg/kg) and escitalopram (5 mg/kg) significantly increased the levels of noradrenaline and serotonin, decreased the level of its metabolite, and did not alter level of dopamine, but decreased the levels of its metabolites. In addition, co-treatment with aripiprazole (0.3 mg/kg) and mirtazapine (10 mg/kg) significantly increased the level of noradrenaline, did not change the levels of dopamine and serotonin, but increased the levels of their metabolites. Based on these results, the increase in the extracellular levels of noradrenaline or serotonin in the cortex induced by co-treatment with an antidepressant and aripiprazole may be very important for the pharmacotherapy of negative and some cognitive symptoms of schizophrenia.

The effect of risperidone on the mirtazapine-induced changes in extracellular monoamines in the rat frontal cortex

BACKGROUND

The aim of our study was to understand the mechanism of clinical efficacy of the combination of an antidepressant and risperidone in drug-resistant depression.

METHODS

We studied the effect of an antidepressant (mirtazapine) and risperidone (atypical antipsychotic), given separately or jointly on extracellular levels of dopamine (DA), serotonin (5-HT) and noradrenaline (NA) in the rat frontal cortex. The animals were given a single intraperitoneal injection of risperidone (1mg/kg) and mirtazapine (10 and 20mg/kg). The release of monoamines in the rat frontal cortex was investigated using a microdialysis in freely moving animals, and monoamine levels were assayed by HPLC with coulochemical detection.

RESULTS

Risperidone increased the cortical extracellular levels of DA, 5-HT and NA. Similarly, mirtazapine dose-dependently increased the cortical extracellular levels of the monoamines studied. A combination of mirtazapine either at the higher dose (20mg/kg) or at both doses (10 and 20mg/kg) with risperidone produced a significant effect on DA and NA release, respectively compared to the effect of any drug given alone. The increase in the DA (but not NA) release induced by mirtazapine plus risperidone was partly blocked by the selective 5-HT1A antagonist WAY 100635 (0.2mg/kg).

CONCLUSIONS

Our data indicate that the increase of cortical extracellular levels of DA and NA by combined administration of mirtazapine and risperidone may be of crucial importance to the pharmacotherapy of drug resistant depression, and that, among other mechanisms, 5-HT1A, 5-HT2A, α2-adrenergic and histamine H1 receptors may play some role in this effect.

Metabolic drug interactions with newer antipsychotics: a comparative review

Newer antipsychotics introduced in clinical practice in recent years include clozapine, risperidone, olanzapine, quetiapine, sertindole, ziprasidone, aripiprazole and amisulpride. These agents are subject to drug-drug interactions with other psychotropic agents or with medications used in the treatment of concomitant physical illnesses. Most pharmacokinetic interactions with newer antipsychotics occur at the metabolic level and usually involve changes in the activity of the major drug-metabolizing enzymes involved in their biotransformation, i.e. the cytochrome P450 (CYP) monooxygenases and/or uridine diphosphate-glucuronosyltransferases (UGT). Clozapine is metabolized primarily by CYP1A2, with additional contribution by other CYP isoforms. Risperidone is metabolized primarily by CYP2D6 and, to a lesser extent, CYP3A4. Olanzapine undergoes both direct conjugation and CYP1A2-mediated oxidation. Quetiapine is metabolized by CYP3A4, while sertindole and aripiprazole are metabolized by CYP2D6 and CYP3A4. Ziprasidone pathways include aldehyde oxidase-mediated reduction and CYP3A4-mediated oxidation. Amisulpride is primarily excreted in the urine and undergoes relatively little metabolism. While novel antipsychotics are unlikely to interfere with the elimination of other drugs, co-administration of inhibitors or inducers of the major enzymes responsible for their metabolism may modify their plasma concentrations, leading to potentially significant effects. Most documented metabolic interactions involve antidepressant and anti-epileptic drugs. Of a particular clinical significance is the interaction between fluvoxamine, a potent CYP1A2 inhibitor, and clozapine. Differences in the interaction potential among the novel antipsychotics currently available may be predicted based on their metabolic pathways. The clinical relevance of these interactions should be interpreted in relation to the relative width of their therapeutic index. Avoidance of unnecessary polypharmacy, knowledge of the interaction profiles of individual agents, and careful individualization of dosage based on close evaluation of clinical response and, possibly, plasma drug concentrations are essential to prevent and minimize potentially adverse drug interactions in patients receiving newer antipsychotics.

Risperidone augmentation of clozapine: a critical review

OBJECTIVE

Atypical antipsychotics are frequently used as augmentation agents in clozapine-resistant schizophrenic patients. Risperidone (RIS) is the one most studied as a clozapine (CLZ) adjunct. The aim of this study is to critically review all published studies regarding the efficacy and safety of RIS as an adjunctive agent in CLZ-resistant schizophrenic or schizoaffective patients.

METHODS

A MEDLINE search from January 1988 to June 2005 was conducted. Identified papers were examined against several clinical, pharmacological and methodological parameters.

RESULTS

A total of 15 studies were found (2 randomized controlled trials, 3 open-label trials (OTs) and 8 case-studies (CSs)) comprising 86 schizophrenic or schizoaffective patients (mean age 38.4 years). Mean CLZ dosage during the combined treatment was 474.2 mg/day. Plasma CLZ levels were assessed in 62 patients (72.1%). RIS was added at a mean dosage of 4.6 mg/day for a mean of 7.9 weeks. Significant improvement in psychopathology was reported for 37 patients (43%). A lower RIS dosage and a longer duration of the trial seemed to be associated with a better outcome. Main side effects reported were: extrapyramidal symptoms or akathisia (9.3%), sedation (7%) and hypersalivation (5.8%).

CONCLUSIONS

Existing evidence encourages the use of RIS as an adjunctive agent in CLZ-resistant schizophrenic or schizoaffective patients.

Randomized controlled augmentation trials in clozapine-resistant schizophrenic patients: a critical review

Approximately 40-70% of treatment-resistant schizophrenic patients fail to benefit from clozapine monotherapy or are partial responders. During the last years several clozapine adjunctive agents have come into clinical practice. This study aims to critically review all published randomized, double-blind, placebo-controlled clinical trials (RCTs) regarding the efficacy and safety of adjunctive agents in clozapine-resistant schizophrenic or schizoaffective patients. A MEDLINE search for RCTs on clozapine adjunctive agents published from January 1980 to February 2004 was conducted. All identified papers were critically reviewed and examined against several methodological features as well as clinical and pharmacological parameters. Eleven trials including 270 patients, partial or non-responders to clozapine, assessed the efficacy of sulpiride, lithium, lamotrigine, fluoxetine, glycine, d-serine, d-cycloserine and ethyl-eicosapentanoate (E-EPA) as clozapine adjuncts. There were eight parallel-group and three crossover trials. The inclusion criteria varied widely. The duration as well as the dosage of clozapine monotherapy were reported adequate in only one trial. Plasma clozapine levels were assessed in only three trials. Main side-effects reported were hypersalivation, sedation, diarrhea, nausea, hyperprolactinaemia. The outcome favored clozapine augmentation with sulpiride, lamotrigine and E-EPA. Lithium was shown to benefit only schizoaffective patients. However, the methodological shortcomings of trials analyzed limit the impact of evidence provided.

Olanzapine augmentation in treatment-resistant panic disorder: a 12-week, fixed-dose, open-label trial

The purpose of our study was to evaluate the efficacy and tolerability of low-dose olanzapine augmentation in selective serotonin reuptake inhibitor (SSRI)-resistant panic disorder (PD) with or without agoraphobia. In this 12-week, open-label study, 31 adult outpatients with treatment-resistant PD who had previously failed to respond to SSRI treatment were treated with fixed dose of olanzapine (5 mg/d) in addition to SSRI. Efficacy was assessed using the Panic Attack and Anticipatory Anxiety Scale (PAAAS), the Agoraphobic Cognitions Questionnaire (ACQ), the Hamilton Rating Scale for Anxiety (HAM-A), the Hamilton Rating Scale for Depression (HAM-D), the Global Assessment of Functioning Scale (GAF), and the Clinical Global Impression of Improvement (CGI-I). Twenty-six patients completed the trial period with a dropout rate of 16.1%. At week 12, 21 patients were responders (81.8%), and an overall improvement on all rating scales was observed in all patients both with or without agoraphobia. Fifteen patients (57.7%) achieved remission. Olanzapine was well tolerated and the most frequent adverse effects were mild-to-moderate weight gain and drowsiness. No extrapyramidal symptoms were reported. Olanzapine appears to be effective as augmentation strategy in the treatment of SSRI-resistant PD, but study limitations must be considered and placebo-controlled studies are needed.

A case of clozapine-induced tonic-clonic seizures managed with valproate: implications for clinical care

We describe a case of clozapine-induced seizures in a patient with treatment-resistant schizophrenia. She had previously been treated unsuccessfully with a number of atypical antipsychotic medications, before she was eventually started on clozapine. She experienced two separate episodes of observed fits whilst on an initial daily dose of 125 mg and, subsequently, on a daily dose of 237.5 mg. Following discontinuation of clozapine, she was rechallenged and again was observed to have seizures. Appropriate investigations ruled out any organic cause of the fits and clozapine was successfully restarted, together with sodium valproate. By the time of treatment stabilization, the patient had not experienced any further fits. These findings suggest that clozapine-induced seizures can be successfully treated, that gradual dose titration can reduce the likelihood of further episodes of seizures and that concomitant use of a suitable mood stabilizer/anti-epileptic medication can improve the outcome of treatment-resistant schizophrenia. Furthermore, the concomitant use of fluoxetine and clozapine is discouraged, with citalopram suggested as a suitable antidepressant in those depressed patients receiving clozapine.

Metabolic drug interactions with new psychotropic agents

New psychotropic drugs introduced in clinical practice in recent years include new antidepressants, such as selective serotonin reuptake inhibitors (SSRI) and 'third generation' antidepressants, and atypical antipsychotics, i.e. clozapine, risperidone, olanzapine, quetiapine, ziprasidone and amisulpride. These agents are extensively metabolized in the liver by cytochrome P450 (CYP) enzymes and are therefore susceptible to metabolically based drug interactions with other psychotropic medications or with compounds used for the treatment of concomitant somatic illnesses. New antidepressants differ in their potential for metabolic drug interactions. Fluoxetine and paroxetine are potent inhibitors of CYP2D6, fluvoxamine markedly inhibits CYP1A2 and CYP2C19, while nefazodone is a potent inhibitor of CYP3A4. These antidepressants may be involved in clinically significant interactions when coadministered with substrates of these isoforms, especially those with a narrow therapeutic index. Other new antidepressants including sertraline, citalopram, venlafaxine, mirtazapine and reboxetine are weak in vitro inhibitors of the different CYP isoforms and appear to have less propensity for important metabolic interactions. The new atypical antipsychotics do not affect significantly the activity of CYP isoenzymes and are not expected to impair the elimination of other medications. Conversely, coadministration of inhibitors or inducers of the CYP isoenzymes involved in metabolism of the various antipsychotic compounds may alter their plasma concentrations, possibly leading to clinically significant effects. The potential for metabolically based drug interactions of any new psychotropic agent may be anticipated on the basis of knowledge about the CYP enzymes responsible for its metabolism and about its effect on the activity of these enzymes. This information is essential for rational prescribing and may guide selection of an appropriate compound which is less likely to interact with already taken medication(s).

Olanzapine augmentation of paroxetine-refractory obsessive-compulsive disorder

The aim of the present study was to investigate the effect of adjunctive olanzapine in patients with obsessive-compulsive disorder (OCD) refractory to paroxetine. Twenty-one patients unresponsive to treatment with paroxetine, administered for at least 12 weeks at the dose of 60 mg/day, participated to a 12-week open-label, add-on trial with olanzapine (10 mg/day). The psychopathological state was evaluated by the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and by Clinical Global Impression (CGI). Three patients did not complete the 12-week adjunctive treatment with olanzapine. In the 18 completers, the mean Y-BOCS score decreased significantly from 27.1+/-4.0 at baseline to 20.1+/-3.9 at final evaluation (P<.001). Seven patients (38.9%) were rated as responders at final evaluation. Steady-state plasma concentrations of paroxetine were not modified during olanzapine coadministration. The drug combination was generally well tolerated and initial sedation and weight gain were the most frequent unwanted effects. Our findings confirm the results of previous studies and indicate that the addition of olanzapine to ongoing treatment with serotonin reuptake inhibitors (SRI) may be beneficial in some patients unresponsive to SRI monotherapy.