T174. ANTIPSYCHOTICS AND THE MICROBIOME

Abstract Background Gut microbial diversity is influenced by many factors including aging and environmental factors and it has an important implication on various physiologic functions and disease processes. Studying microbial communities and its diversity may be used as a predictor or biomarker for disease development. Methods In-depth literature review was conducted of literature within the last 5 years via database search of Pubmed, PsycInfo, EMBASE, and Google Scholar with Boolean combinations of the following keywords: antipsychotics AND (microbiome OR “metabolic syndrome”), microbiome AND (gender OR aging). Results 2,360 articles were initially retrieved. 27 articles remained after excluding for non-English articles and relevance. Notable findings include that patients treated with both risperidone and olanzapine have less diverse microbiomes with a higher ratio of Firmicutes to Bacteroidetes. Additionally, patients treated with olanzapine have been shown to have increased actinobacteria and increased ratio of Firmicutes to Bacteroidetes. The ratio of Firmicutes to Bacteroidetes correlates directly to the extent of olanzapine induced weight gain. Patients concurrently treated with olanzapine and antibiotics not only stopped weight gain but also reversed it. This has been a target of potential medication intervention, specifically focused on antagonism of histamine-1 and -3 receptors which is speculated to inhibit the askewed Firmicutes to Bacteroidetes ratio. Similarly, the gender differences in relative microbiome levels of Bacteroidetes are suspected to correlate to the increased olanzapine induced weight gain seen in women versus men. Additionally, patients with schizophrenia who were treated with Bifidobacterium breve A1, a probiotic supplement, showed improvements in their affective, positive, and negative symptoms. Discussion There is a large paucity of research into the relationship between the microbiome and psychotropic medications. This dynamic should be further studied within multiple populations to better understand the gut biome’s effects on psychiatric disorders.