Clozapine is the only approved drug for treatment-resistant schizophrenia, but the response to the drug is often inadequate. Augmentation with other antipsychotics, anticonvulsants, and antidepressants is recommended for such patients, but there is a lack of evidence regarding the most effective therapy. This network meta-analysis was conducted to evaluate the efficacy of pharmacological agents used in the augmentation strategies in patients who were partial/ non-responders to clozapine. Relevant data were extracted from 30 randomized controlled trials through searches of electronic databases (MEDLINE/PubMed, Embase, Cochrane, clinical trial registries). PRISMA guidelines were followed for the extraction, management, analysis, and reporting of the data. The outcome measure in this study was a reduction in symptom severity according to total PANSS/BPRS and was reported as the standardized mean difference with a 95% credible interval. Bayesian network meta-analysis with random effects model and uninformative priors was conducted, and the ranking probability of each intervention was done. Meta-regression was done to assess the effect of duration on the reduction in symptom severity scores. Mirtazapine (-5.2 [95%CrI: -7.7, -2.7]) and memantine (-2.1 [95%CrI: -4.0, -0.19]] were more efficacious than placebo for augmentation of clozapine in partial/non-responders and were the most effective adjunctive agents as per SUCRA scores. Both drugs did not cause a significant increase in frequency of adverse events compared to placebo. There was a significant effect of duration on the reduction in symptom severity. There was no evident publication bias. Mirtazapine and memantine may prove beneficial for augmentation of clozapine in non/partial responders to monotherapy.
Keywords: Augmentation therapy; Clozapine; Clozapine-resistant; Schizophrenia.