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.

References

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

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