Irritable bowel syndrome: Epidemiology, overlap disorders, pathophysiology and treatment

Table 1 Summary of irritable bowel syndrome medications

Type	Mechanism of action	Example	Appearing dose	Efficient
IBS-D
Opioid agents	Inhibits secretion, transit	Loperamide	4 mg tid	Unknown for IBS; effective for diarrhea	First-line
		Eluxadoline	75 mg or 100 mg bid	Effective for FDA composite: 100 mg: OR, 0.87 (95%CI: 0.83-0.91); 75 mg: OR, 0.89 (95%CI: 0.84-0.94). RCTs: Effective for diarrhea and composite diarrhea + pain; not pain alone
Bile acid sequestrants	Bind to bile acids	Cholestyramine	4 g bid	Unknown: effective in open-label studies; ineffective in 1, single-center RCT
		Colestipol	-
		Colesevelam	32 mg bid
Antibiotic	Anti-inflammatory	Rifaximin	550 mg tid	Effective: In 2012 SRMA: Global: OR 1.57 (1.22 to 2.01); Bloating: OR 1.55 (1.23 to 1.96); In 2020 SRMA: FDA composite: OR: 0.92 (0.86 to 0.98) Global OR: 0.91 (0.77, 1.07)	Second-line
5-HT3	Delays colonic transit and reduces visceral pain	Alosetron	0.5-1 mg qd or 1 mg bid	Effective: Global RR 1.60 (1.49 to 1.72); Pain RR 1.30 (1.22 to 1.39); FDA composite: OR 0.69 (0.60 to 0.80)	Third-line
Receptor antagonists		Ramosetron	2.5 µg qd
IBS-C
Osmotic	Osmotic secretion	PEG3350	-	Effective: improves SBMs, CSBMs, consistency straining but not pain, bloating or incomplete evacuation	First-line
Secretory	Increased Cl- and water secretion	Lubiprostone	8 µg bid	Effective: Lubiprostone 8 µg RR: 0.85 (0.78 to 0.96) for FDA endpoint	Second-line
		Linaclotide	290 mg qd	Effective: Adequate relief IBS: RR 1.95 (1.3 to 2.9); Abdo pain: RR 1.58 (1.02 to 2.46) RR 0.81 (0.76 to 0.86) for 290 µg for FDA endpoint
		Plecanatide	3 mg/6 mg qd	Effective: Using FDA endpoint 6 mg: RR 0.87 (0.81 to 0.94); 3 mg RR 0.88 (0.82 to 0.94)
Anti-absorptive	NHE3 inhibitor stimulates Na+, water secretion	Tenapanor	15mg bid	Effective at 50 mg 2/d; NNT, 7-9 for complete SBM and combined complete SBM ≥ 30% pain reduction; 11 for abdominal pain reduction > 30% alone	Third-line
Pain
Anti-spasmodics	Inhibition of muscarinic Ach receptors or block Ca++ channels, relaxation of GI smooth muscle	Pinaverium	50 mg tid	May be effective: OR, 0.68 (95%CI: 0.57-0.71); overall NNT, 5	First-line
		Otilonium	20/40/80 mg tid
		Hyoscine	-
		Peppermint Oil	182 mg	Effective: OR, 0.43 (95%CI: 0.32-0.59); Global: RR 2.23 (95%CI: 1.78-2.81); overall NNT, 2.5; RCT of sustained release formulation: decrease pain, bloat, urgency but not total IBS scores
Antidepressants	Psychological, acting on the CNS	TCA	-	Effective: OR, 0.67 (95%CI: 0.58-0.77); for global: OR, 0.62 (95%CI: 0.43-0.88); NNT, 4 for abdominal pain	Second-line
		SSRI	-

Adapted from Camilleri et al[82]. Ach: Acetylcholine; 5-HT3: Serotonin type 3; IBS: Irritable bowel syndrome; IBS-C: Constipation; IBS-D: Diarrhea; IBS-M: Mixed symptoms; NHE3: Sodium-hydrogen exchanger 3; OR: Odds ratio; PEG 3350: Polyethylene glycol 3350; RCT: Randomized clinical trial; RR: Relative risk; Rx: Prescription; SSRI: Selective serotonin reuptake inhibitor; SBM: Spontaneous bowel movement; SRMA: Systematic review and meta-analysis; TCA: Tricyclic antidepressant.