Abstract
The gut microbiome is a critical part of host homeostasis, yet its resilience following opioid exposure remains poorly understood. While opioid-induced short-term dysbiosis is well documented, the long-term recovery dynamics following oxycodone remain unclear. This study characterized the temporal dynamics of the fecal microbiota in male C57BL/6J mice following a brief 3-day oxycodone regimen (5 mg/kg, twice daily). 16S rRNA gene sequencing was performed at baseline, day 3, 10, 17, and 70. While acute post-treatment phases (day 3–10) showed subtle taxonomic shifts in Clostridium_sensu_stricto_1 and Romboutsia , significant community disruption emerged later. By day 17, beta diversity significantly differed from saline controls (p=0.002). At day 70, both alpha diversity (p=0.02) and beta diversity (p=0.007) remained significantly altered, characterized by enriched Akkermansia and Marvinbryantia alongside depleted Eubacterium_xylanophilum . These findings demonstrate that even brief oxycodone exposure triggers persistent, non-recovering dysbiosis that became detectable only after treatment cessation and persisted through day 70. This suggests that the window for microbiome recovery exceeds two months in mice (equivalent to several human years), highlighting a potential long-term risk for patients prescribed short-term opioid courses.