Meta-Analysis Conundrums

For patients whose psychosis doesn’t adequately respond to antipsychotics, especially clozapine, treatment options include electroconvulsive therapy, cognitive-behavior therapy, and augmentation with another medication. Investigators have done cotreatment trials with other antipsychotics, anticonvulsant/mood stabilizers, and even the antibiotic minocycline and anti-inflammatory agents such as aspirin. The trials are small in many cases, so meta-analyses allow various trials to be pooled. Two recent publications give some new guidance but also may sow confusion.

One team examined clinical trials of the anticonvulsants lamotrigine, topirimate and valproate added to clozapine. They included 22 randomized controlled trials (RCTs) comprising 1227 subjects; 613 received clozapine alone, whereas the others received, in order of frequency, valproate, lamotrigine or topirimate. The primary outcome was change in Positive and Negative Syndrome Scale (PANSS) or Brief Psychiatric Rating Scale (BPRS) total score. The analysis showed no significant effect for lamotrigine, confirming a previous meta-analysis, but also confirming a prior analysis, topirimate was superior to clozapine alone for reduction in total, positive and negative psychotic symptoms ratings. Sodium valproate, but not magnesium valproate, was superior to clozapine alone in reducing total and positive psychotic symptom scores; it was not effective for negative symptoms. In terms of tolerability, topirimate but not valproate had a significant all-cause discontinuation rate compared to clozapine monotherapy.

One of the limitations of this pooled data set was that many of the patients were not clearly designated as having clozapine resistance; for instance, clozapine serum levels were not recorded. Another concern was that all the trials for valproate augmentation were done in China, and the generalizability to other settings and ethnic groups is uncertain.

The anticonvulsant meta-analysis is one of many that has examined antipsychotic augmentation, which prompted a group led by Christoph Correll to do a meta-meta-analysis. Summarizing this article will not do it justice, so I recommend reading it in its entirety. The investigators looked at 29 existing meta-analyses of trials of augmentation of any antipsychotic with any of 42 medications including, mood stabilizers, anticonvulsants, antidepressants, minocycline, a second antipsychotic, or various hormones such as estrogenic agents. They applied a novel method to assess the quality of the meta-analyses, AMSTAR-Plus Content. Five of the meta-analyses looked at augmentation of clozapine.

In combination with clozapine for positive symptoms of psychosis, only glycine, an amino acid which modulates the NMDA glutamate receptor, had a significant effect size. No treatments showed efficacy in combination with clozapine for total psychopathology or negative symptom scores. In combination with non-clozapine antipsychotics, lamotrigine, estrogenic agents, mirtazapine and a few others showed efficacy.

An important finding is buried in the discussion: “When all this metanalytic literature was compared regarding the quality of its meta-analyzed content, the effect sizes were inversely correlated with the study quality, reducing confidence in these affirmative recommendations.” In other words, many of the studies in this uber-study were small or contained biases, and those studies tended to overrate the effects of the adjunctive treatments. They point out that individual patients may benefit from specific interventions, but the evidence to guide treatment selection is lacking. This leaves the clinician without clear direction for the most difficult-to-treat patients. In an accompanying editorial, however, Wolfgang Fleishhacker suggests that this meta-analysis does not necessarily invalidate all preceding analyses.


Zheng W, Xiang YT, Yang XH, Xiang YQ, de Leon J. Clozapine Augmentation with Antiepileptic Drugs for Treatment-Resistant Schizophrenia: A Meta-Analysis of Randomized Controlled Trials. J Clin Psychiatry. 2017;78(5):e498-e505. Abstract

Correll CU, Rubio JM, Inczedy-Farkas G, Birnbaum ML, Kane JM, Leucht S. Efficacy of 42 Pharmacologic Cotreatment Strategies Added to Antipsychotic Monotherapy in Schizophrenia: Systematic Overview and Quality Appraisal of the Meta-Analytic Evidence. JAMA Psychiatry. 2017;74(7):675-684. Astract

Does lamotrigine augment clozapine?

Many of the patients referred to B.C psychosis Program are on clozapine or have received it in the past, and many have had a limited response. Clozapine-resistance is a big challenge for psychiatrists who manage chronic psychosis, and a recent quantitative review of clozapine augmentation strategies provides little guidance or solace. Stefan Leucht and colleagues examined randomized, masked, placebo-controlled studies

of at least two weeks duration in which another drug was added following at least four weeks of  clozapine therapy. Whenever possible, they used intention-to-treat data to calculate effect size.

The studies involved a range of medications including antidepressants, antipsychotics, glutamatergic agents, and antiepileptics. Lamotrigine is particularly of interest because Tiihonen’s group performed a meta-analysis in 2009 based on five studies that showed a significant effect for augmentation of clozapine. This group obtained unpublished data from studies that looked at lamotrigine added to a variety of antipsychotics, and intention-to-treat outcomes from the trial by Zocali, the largest study to date with 30 subjects on active therapy. Based on the 2009 meta-analysis, Goff commented that “the addition of lamotrigine in patients who remain symptomatic despite adequate clozapine treatment represents the most promising treatment option currently available.”

Although Tiihonen et al. found insignificant heterogeneity, Leucht et al. did find heterogeneity and concluded that the Zocali study was an outlier. They therefore excluded it from their final analysis. This is the crucial difference between the two meta-analyses and the reason for the sharply divergent conclusions. Four studies of lamotrigine augmentation are negative and one is positive. A closer look reveals that the Zocali trial was 24 weeks in duration, whereas the other trials were 10 to 14 weeks; could this be a crucial difference? Goff is still correct, and rather than throw lamotrigine overboard, we need a replication trial lasting 24 or 30 weeks. We know that the benefits of clozapine may take many months to be fully evident, so we should not expect that clozapine augmentation to be a quick affair.

As for other findings of the Leucht meta-analysis, sulpiride augmentation showed significant impact on both positive and negative symptoms, and citalopram showed significant impact on negative symptoms, but the findings are based on one trial each. A trial of an experimental glutamatergic agent showed a signal. This leaves us with few clear optins but some direction for further research.


Sommer IE, Begemann MJ, Temmerman A, Leucht S. Pharmacological augmentation strategies for schizophrenia patients with insufficient response to clozapine: a quantitative literature review. Schizophr Bull. Mar 21 2011; Epub ahead of print; doi:10.1093/schbul/sbr004

Tiihonen J, Wahlbeck K, Kiviniemi V. The efficacy of lamotrigine in clozapine-resistant schizophrenia: A systematic review and meta-analysis. Schizophr Res. 2009;109:10–14.

Goff DC. Review: lamotrigine may be an effective treatment for clozapine resistant schizophrenia. Evid Based Mental Health. 2009;12:111.

Zoccali R,Muscatello MR,Bruno A, Cambria R, et al. The effect of lamotrigine augmentation of clozapine in a sample of treatment-resistant schizophrenic patients: a double-blind, placebo-controlled study. Schizophr Res. 2007;93:109–116.