Table 2.

Bacterial groups impacted by fentanyl intravenous self-administration (IVSA).

Bacterial Phylum or Genus	Results
Verrucomicrobia	Decreased after fentanyl IVSA (males, 1.25 μg/kg/infusion; p = 0.03) Increased in females vs. males before fentanyl IVSA (p = 0.01)
Prevotella	Increased after fentanyl IVSA (females, 1.25 μg/kg/infusion; p = 0.02) Decreased in females vs. males before fentanyl IVSA (p = 0.02)
Ruminococcus	Increased after fentanyl IVSA (males, 1.25 μg/kg/infusion; p = 0.03)
Akkermansia	Decreased after fentanyl IVSA (males, 1.25 μg/kg/infusion; p = 0.03) Increased in females vs. males before fentanyl IVSA (p = 0.01)