The atypical antipsychotics lurasidone and olanzapine exert contrasting effects on the gut microbiome and metabolic function of rats

Abstract Background and Purpose Antipsychotics such as olanzapine are associated with significant metabolic dysfunction, attributed to gut microbiome dysbiosis. A recent notion that most psychotropics are detrimental to the gut microbiome has arisen from consistent findings of metabolic adverse effects. However, unlike olanzapine, the metabolic effects of lurasidone are conflicting. Thus, this study investigates the contrasting effects of olanzapine and lurasidone on the gut microbiome to explore the hypothesis of ‘gut neutrality’ for lurasidone exposure. Experimental Approach Using Sprague–Dawley rats, the effects of olanzapine and lurasidone on the gut microbiome were explored. Faecal and blood samples were collected weekly over a 21‐day period to analyse changes to the gut microbiome and related metabolic markers. Key Results Lurasidone triggered no significant weight gain or metabolic alterations, instead positively modulating the gut microbiome through increases in mean operational taxonomical units (OTUs) and alpha diversity. This novel finding suggests an underlying mechanism for lurasidone's metabolic inertia. In contrast, olanzapine triggered a statistically significant decrease in mean OTUs, substantial compositional variation and a depletion in short‐chain fatty acid abundance. Microbiome depletion correlated with metabolic dysfunction, producing a 30% increase in weight gain, increased pro‐inflammatory cytokine expression, and increased blood glycaemic and triglyceride levels. Conclusion and Implications Our results challenge the notion that all antipsychotics disrupt the gut microbiome similarly and highlights the potential benefits of gut‐neutral antipsychotics, such as lurasidone, in managing metabolic side effects. Further research is warranted to validate these findings in humans to guide personalised pharmacological treatment regimens for schizophrenia.