Table 2.

Changes in the microbiome composition of subjects with OIC or with constipation not related to opioid use.

Bacteria	Opioid Treatment	Reference	Note Subject	Constipation	Reference	Note Type of Constipation
Firmicutes Bacteroidetes	↑ ↓	[165] [163]	Sprague Dawley rat (oxycodone 2 mg/kg s.c. twice a day for 5 days)	↑ ↓	[166]	Irritable bowel syndrome patients with constipation.
			C57BL/6 mouse (loperamide 9.6 mg/kg p.o., twice a day for 14 days)
Bifidobacterium, Lactobacillus	↓	[167]	C57BL/6 mouse (escalating doses of morphine from 5 to 40 mg/kg, twice/day for 8 days)	↓	[168]	Patients with functional constipation
Lactobacillus, Bacteroides and Akkermansia	↓ ↑	[169]	C57BL/6 mouse (hydromorphone 7.5 mg/kg twice a day for 8 days)	↓ ↑	[96]	Mice received fecal microbiota from patients with constipation
Bacteroidetes, Lactobacillus, and Clostridium	↓	[127]	C57BL/6 mouse (25 mg morphine pellet implanted for 3 days)	↓	[168,170]	Adult patients with functional constipation
Ruminococcus, Clostridium spp.	↑	[171]	C57BL/6 mouse (intermittent and sustained morphine)	↑	[172]	Children with functional constipation
Roseburia Enterobacteriaceae	↓ ↑	[164]	Patients (heroin or prescription opioids)	↓ ↑	[173]	Patients with constipated-irritable bowel syndrome
Roseburia	↓	[164] [174]	Patients (heroin or prescription opioids)	↓	[175] [176] [177]	Patients with severe chronic constipation Italian subjects with functional constipation
			C57BL/6 pregnant mouse (10 mg/kg hydromorphone i.p. for 3 days, on gestation days G11-G13)			Constipated Women of Reproductive Age