The Tolerability of Mirtazapine Augmentation in Schizophrenic Patients Treated with Risperidone: A Preliminary Randomized Placebo-controlled Trial

Mirtazapine in schizophrenia - an undeservedly overlooked option?

Mirtazapine has often been prescribed as add-on treatment for schizophrenia in patients with suboptimal response to conventional treatments. In this review, we evaluate the existing evidence for efficacy and effectiveness of add-on mirtazapine in schizophrenia and reappraise the practical and theoretical aspects of mirtazapine-antipsychotic combinations. In randomized controlled trials (RCTs), mirtazapine demonstrated favourable effects on negative and cognitive (although plausibly not depressive) symptoms, with no risk of psychotic exacerbation. Mirtazapine also may have a desirable effect on antipsychotic-induced sexual dysfunction, but seems not to alleviate extrapyramidal symptoms, at least if combined with second-generation antipsychotics. It is noteworthy that all published RCTs have been underpowered and relatively short in duration. In the only large pragmatic effectiveness study that provided analyses by add-on antidepressant, only mirtazapine was associated with both decreased rate of hospital admissions and number of in-patient days. Mirtazapine hardly affects the pharmacokinetics of antipsychotics. However, possible pharmacodynamic interactions (sedation and metabolic offence) should be borne in mind. The observed desired clinical effects of mirtazapine may be due to its specific receptor-blocking properties. Alternative theoretical explanations include its possible neuroprotective effect. Further well-designed RCTs and real-world effectiveness studies are needed to determine whether add-on mirtazapine should be recommended for difficult-to-treat schizophrenia.

Mirtazapine adjunct for people with schizophrenia

BACKGROUND

Many individuals who have a diagnosis of schizophrenia experience a range of distressing and debilitating symptoms. These can include positive symptoms (such as delusions, hallucinations, disorganised speech), cognitive symptoms (such as trouble focusing or paying attention or using information to make decisions), and negative symptoms (such as diminished emotional expression, avolition, alogia, and anhedonia). Antipsychotic drugs are often only partially effective, particularly in treating negative symptoms, indicating the need for additional treatment. Mirtazapine is an antidepressant drug that when taken in addition to an antipsychotic may offer some benefit for negative symptoms.

OBJECTIVES

To systematically assess the effects of mirtazapine as adjunct treatment for people with schizophrenia.

SEARCH METHODS

The Information Specialist of Cochrane Schizophrenia searched the Cochrane Schizophrenia Group's Study-Based Register of Trials (including registries of clinical trials) up to May 2018.

SELECTION CRITERIA

All randomised-controlled trials (RCTs) with useable data focusing on mirtazapine adjunct for people with schizophrenia.

DATA COLLECTION AND ANALYSIS

We extracted data independently. For binary outcomes, we calculated risk ratio (RR) and its 95% confidence interval (CI), on an intention-to-treat (ITT) basis. For continuous data, we estimated the mean difference (MD) between groups and its 95% CI. We employed a fixed-effect model for analyses. For included studies we assessed risk of bias and created 'Summary of findings' table using GRADE.

MAIN RESULTS

We included nine RCTs with a total of 310 participants. All studies compared mirtazapine adjunct with placebo adjunct and were of short-term duration. We considered five studies to have a high risk of bias for either incomplete outcome data, selective reporting, or other bias.Our main outcomes of interest were clinically important change in mental state (negative and positive symptoms), leaving the study early for any reason, clinically important change in global state, clinically important change in quality of life, number of days in hospital and incidence of serious adverse events.One trial defined a reduction in the Scale for the Assessment of Negative Symptoms (SANS) overall score from baseline of at least 20% as no important response for negative symptoms. There was no evidence of a clear difference between the two treatments with similar numbers of participants from each group showing no important response to treatment (RR 0.81, 95% CI 0.57 to 1.14, 1 RCT, n = 20, very low-quality evidence).Clinically important change in positive symptoms was not reported, however, clinically important change in overall mental state was reported by two trials and data for this outcome showed a favourable effect for mirtazapine (RR 0.69, 95% CI 0.51 to 0.92; I² = 75%, 2 RCTs, n = 77, very low-quality evidence). There was no evidence of a clear difference for numbers of participants leaving the study early (RR 1.03, 95% CI 0.64 to 1.66, 9 RCTs, n = 310, moderate-quality evidence), and no evidence of a clear difference in global state Clinical Global Impressions Scale (CGI) severity scores (MD -0.10, 95% CI -0.68 to 0.48, 1 RCT, n = 39, very low-quality evidence). A favourable effect for mirtazapine adjunct was found for the outcome clinically important change in akathisia (RR 0.33, 95% CI 0.20 to 0.52, 2 RCTs, n = 86, low-quality evidence; I² = 61%I). No data were reported for quality life or number of days in hospital.In addition to the main outcomes of interest, there was evidence relating to adverse events that the mirtazapine adjunct groups were associated with an increased risk of weight gain (RR 3.19, 95% CI 1.17 to 8.65, 4 RCTs, n = 127) and sedation/drowsiness (RR 1.64, 95% CI 1.01 to 2.68, 7 RCTs, n = 223).

AUTHORS' CONCLUSIONS

The available evidence is primarily of very low quality and indicates that mirtazapine adjunct is not clearly associated with an effect for negative symptoms, but there is some indication of a positive effect on overall mental state and akathisia. No effect was found for global state or leaving the study early and data were not available for quality of life or service use. Due to limitations of the quality and applicability of the evidence it is not possible to make any firm conclusions, the role of mirtazapine adjunct in routine clinical practice remains unclear. This underscores the need for new high-quality evidence to further evaluate mirtazapine adjunct for schizophrenia.

Randomized Controlled Trials of Add-On Antidepressants in Schizophrenia

BACKGROUND

Despite adequate treatment with antipsychotics, a substantial number of patients with schizophrenia demonstrate only suboptimal clinical outcome. To overcome this challenge, various psychopharmacological combination strategies have been used, including antidepressants added to antipsychotics.

METHODS

To analyze the efficacy of add-on antidepressants for the treatment of negative, positive, cognitive, depressive, and antipsychotic-induced extrapyramidal symptoms in schizophrenia, published randomized controlled trials assessing the efficacy of adjunctive antidepressants in schizophrenia were reviewed using the following parameters: baseline clinical characteristics and number of patients, their on-going antipsychotic treatment, dosage of the add-on antidepressants, duration of the trial, efficacy measures, and outcomes.

RESULTS

There were 36 randomized controlled trials reported in 41 journal publications (n=1582). The antidepressants used were the selective serotonin reuptake inhibitors, duloxetine, imipramine, mianserin, mirtazapine, nefazodone, reboxetin, trazodone, and bupropion. Mirtazapine and mianserin showed somewhat consistent efficacy for negative symptoms and both seemed to enhance neurocognition. Trazodone and nefazodone appeared to improve the antipsychotics-induced extrapyramidal symptoms. Imipramine and duloxetine tended to improve depressive symptoms. No clear evidence supporting selective serotonin reuptake inhibitors' efficacy on any clinical domain of schizophrenia was found. Add-on antidepressants did not worsen psychosis.

CONCLUSIONS

Despite a substantial number of randomized controlled trials, the overall efficacy of add-on antidepressants in schizophrenia remains uncertain mainly due to methodological issues. Some differences in efficacy on several schizophrenia domains seem, however, to exist and to vary by the antidepressant subgroups--plausibly due to differences in the mechanisms of action. Antidepressants may not worsen the course of psychosis. Better designed, larger, and longer randomized controlled trials are needed.

Antidepressants for cognitive impairment in schizophrenia--a systematic review and meta-analysis

BACKGROUND

Cognitive impairment in schizophrenia is disabling, but current treatment options remain limited.

OBJECTIVE

To meta-analyze the efficacy and safety of adjunctive antidepressants for cognitive impairment in schizophrenia.

DATA SOURCES AND STUDY SELECTION

PubMed, MEDLINE, PsycINFO, and Cochrane Library databases were searched until 12/2013 for randomized controlled trials comparing antidepressant augmentation of antipsychotics with placebo regarding effects on cognitive functioning in schizophrenia.

DATA EXTRACTION

Two authors independently extracted data. Standardized mean differences (SMDs) were calculated for continuous outcomes and risk ratios for categorical outcomes. SMDs of individual cognitive tests were pooled on a study level within domains (primary outcome) and across domains. When results were heterogeneous, random instead of fixed effects models were used.

RESULTS

We meta-analyzed 11 studies (duration = 8.7 ± 3.7 weeks) including 568 patients (mean age = 39.5 ± 6.9 years, males = 67.2%, illness duration = 12.5 ± 8.0 years). Antidepressants included mirtazapine (4 studies; n = 126), citalopram (2 studies; n = 231), fluvoxamine (1 study; n = 47), duloxetine (1 study; n = 40), mianserin (1 study; n = 30), bupropion (1 study; n = 61), and reboxetine (1 study; n = 33). Statistically significant, but clinically negligible, advantages were found for pooled antidepressants compared to placebo in executive function (Hedges' g = 0.17, p = 0.02) and a composite cognition score (Hedges' g = 0.095, p = 0.012). Depression improved with serotonergic antidepressants (p = 0.0009) and selective serotonin reuptake inhibitors (p = 0.009), but not with pooled antidepressants (p = 0.39). Sedation was more common with pooled antidepressants (p = 0.04).

CONCLUSION

Adjunctive antidepressants do not demonstrate clinically significant effects on cognition in schizophrenia patients, however, larger studies, preferably in euthymic schizophrenia patients and using full neurocognitive batteries, are needed to confirm this finding.