Table 2.

Changes in gut microbiota diversity with opioid treatment regimen (animal studies).

Opioid	Dose, dosing regimen	Finding	References
Morphine	25 mg pellet (4 days)	↑Staphylococcus, Enterococcus	Meng et al. (2015)
	25 mg pellet (5–7 days)	↑Enterococcaceae, Staphylococcaceae, Bacillaceae, Streptococcaceae, Erysipelotrichaceae ↓Bacteroidetes, Proteobacteria, Actinobacteria, Acidobacteria, Actinobacteria, Acidobacte	Banerjee et al. (2016)
	10 mg/kg i.p. (4 days)	↑Ruminococcus ↓Lactobacillus	Lee et al. (2018)
	25 mg pellet (3 days)	↑Flavobacterium, Enterococcus, Fusobacterium	Wang et al. (2018)
	75 mg pellet (5 days)	↑Enterobacteriales ↓Bacteroidales, Clostridiales,	Kang et al. (2017)
	5–40 mg pellet (8 days)	↑Allobaculum, Peptostreptococcaceae ↓Lactobacillus, Bifidobacterium	Zhang et al. (2019a)
	10 mg/kg i.p. (12 days)	↑Verrucomicrobia ↓Bacteroides	Zhang et al. (2021)
Oxycodone	2 mg s.c (5 days)	↑Firmicutes ↓Bacteroidetes	Simpson et al. (2020)
Hydromorphone	7.5 mg pellet (8 days)	↑Bacteroides, Enterococcus ↓Lactobacillus, Lachnospiraceae	Sharma et al. (2020)