There is increasing evidence that chronic opioid use leads to maladaptive changes in the composition and localization of gut bacteria. OID has been linked to antinociceptive tolerance development in preclinical models and may therefore identify promising targets for new opioid-sparing strategies. Such developments are critical to curb dose escalations in the clinical setting and combat the ongoing opioid epidemic. The study was done to review the existing literature about OID, including the current evidence regarding its qualitative nature, influence on antinociceptive tolerance, and future prospects.

OID plays a role in the modulation of pain control is increasingly evident. More characterization studies are needed, particularly to improve the resolution of compositional analyses. This will greatly facilitate the identification of causal mechanisms in tolerance development. Nonetheless, the consensus of present literature points to a few prevailing themes regarding OID like a shift in GI microflora toward a phenotype that is pro-inflammatory and deleterious to epithelial barrier integrity, translocation of microbes to the gut wall and other extraintestinal sites, and a pervasive correlation between dysbiosis, activation of pro-inflammatory cascades, and development of antinociceptive tolerance. Current findings further suggest that peripheral components of the pain pathway significantly contribute to this process.

Reference: https://www.jpain.org/article/S1526-5900(19)30877-6/fulltext#seccesectitle0017