The effect of second-generation antipsychotic withdrawal on the occurrence of vacuous chewing movements in animal models: A review.

Introduction: Abrupt discontinuation of antipsychotics is associated with an increased risk of adverse events such as extrapyramidal symptoms in humans. In animal models, vacuous chewing movements may occur after antipsychotic discontinuation. We aim to assess vacuous chewing movements after the discontinuation of second-generation antipsychotics in animal models.
Methods: PubMed, EMBASE, and Web of Science databases were searched for studies since inception until January 2, 2021. In addition, we manually searched references from included and relevant studies. Studies were included if a behavioral assessment of vacuous chewing movements (VCMs) in animal models was performed after discontinuation of a second-generation antipsychotic (SGA). Findings will be reviewed qualitatively and discussed with regard to clinical implications.
Results: 5607 studies were screened and five studies were considered eligible for the qualitative analysis. The five studies reported results of behavioral assessments of VCMs after discontinuation of clozapine, olanzapine, and risperidone. VCMs were not reported to be increased after discontinuation of clozapine and olanzapine. However, VCMs were reported to be increased after discontinuation of higher but not lower dosages of risperidone.
Discussion: These findings, based on a limited series of studies, suggest differences in the occurrence of extrapyramidal symptoms between second-generation antipsychotics. More research is needed to determine the magnitude of differences between antipsychotics and implications for clinical practice in humans.
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