Table 2.

Medications Used in the Treatment of Irritable Bowel Syndrome (IBS).^*

Symptoms and Medication	Initial Dose	Target Dose	Common or Serious Side Effects	Evidence		FDA-Approved
Constipation	mg/day†			For the Symptom	For IBS	For the Symptom	For IBS
Laxatives‡ and secretory stimulators
Polyethylene glycol 3350 (Miralax, Braintree Labs)	17,000	up to 34,000, twice a day	Diarrhea, bloating, cramping	+++	−
Lactulose (Kristalose, Cumberland Pharmaceuticals)	10,000–20,000	20,000–40,000	Diarrhea, bloating, cramping	+++	−
Lubiprostone (Amitiza; Takeda, Sucampo)		24 µg, twice a day	Nausea, diarrhea, headache, abdominal pain and discomfort	+++	−	Yes§	No
Prokinetics
Tegaserod (Zelnorm, Novartis)		6, twice a day	Initial diarrhea, abdominal pain, cardiovascular ischemia (rare)	+++	+++	Yes¶	Yes¶
Diarrhea
Loperamide (Imodium, McNeil)	2	2–8	Constipation	+++	−	Yes	No
Alosetron (Lotronex, GlaxoSmithKline)‖	0.5, twice a day	up to 1, twice a day	Constipation, ischemic colitis (rare)	−	+++	No	Yes
Bloating
Antibiotics
Rifaximin (Salix)		400, three times a day	Abdominal pain, diarrhea, bad taste	−	+	No	No
Probiotics**
Bifidobacterium infantis 35624 (Align, Procter & Gamble)		1 capsule per day	None	+	+	No	No
Pain
Tricyclic antidepressants††			Dry mouth, dizziness, weight gain
Amitriptyline	10, at bedtime	10–75, at bedtime		++	+	No	No
Desipramine	10, at bedtime	10–75, at bedtime		++	+	No	No
Selective serotonin-reuptake inhibitors‡‡			Sexual dysfunction, headache, nausea, sedation, insomnia, sweating, withdrawal symptoms
Paroxetine (Paxil CR, GlaxoSmithKline)		10–60		−	+	No	No
Citalopram (Lexapro, Forest)		5–20		+	+	No	No
Fluoxetine (Prozac, Eli Lilly)		20–40	Somnolence, dizziness, headaches, insomnia	+	−	No	No

^*This list is not exhaustive but includes major medications for which there is evidence from well-designed clinical trials of effectiveness for global IBS symptoms or for individual symptoms (e.g., constipation, diarrhea, or abdominal pain and discomfort). In the columns about evidence, + denotes some evidence from at least one controlled trial, ++ moderate evidence from several controlled trials or from meta-analysis of such trials, +++ strong evidence from well-designed, controlled clinical trials, and − no evidence. FDA denotes Food and Drug Administration.

^†Dosages are in milligrams per day unless otherwise noted.

^‡A wide range of osmotic and irritant laxatives, including fiber products, are available over the counter.

^§Lubiprostone is FDA-approved for the treatment of chronic constipation.

^¶Marketing of tegaserod was suspended by the FDA in March 2007 because of rare cardiovascular side effects but is now available as part of a restricted-access program for women who have constipation-predominant IBS or chronic idiopathic constipation, without known or preexisting heart problems, that is unresponsive to other medications.²¹

^‖Alosetron use is restricted to women with severe diarrhea-predominant IBS, unresponsive to other medications, owing to side effects.

^**Many probiotics are available over the counter and are not listed. Align is a probiotic for which a beneficial effect for IBS symptoms has been shown in a high-quality, randomized, controlled trial.

^††A wide range of tricyclic antidepressants with various side effects and side-effect profiles is available. Two commonly prescribed tricyclic antidepressants are listed. The doses listed are based on clinical experience.

^‡‡Many selective serotonin-reuptake inhibitors are available. Only those that have been evaluated in IBS trials are listed. Also not listed are serotonin–norepinephrine reuptake inhibitors.