Antidiarrheals

Drug	Dosage	Remarks
Antidiarrheal Microorganisms
Bifidobacterium longum¹	165-330 mg PO 24 hourly	Special Instructions May be taken with or without food
Saccharomyces boulardii	250-500 mg PO 24 hourly	Adverse Reactions Dermatologic effects (rash, urticaria, pruritus); Other effects (flatulence, angioedema, shock) Special Instructions Use with caution in patients with diarrhea >2 days, pregnancy, lactation Contraindicated in patients allergic to yeast, immunocompromised patients
Antipropulsives
Diphenoxylate/Atropine sulfate	Diphenoxylate 2.5 mg/Atropine sulfate 0.025 mg per tab 2 tab PO 6 hourly Max dose: 8 tabs/day	Adverse Reactions GI effects (anorexia, nausea/vomiting, abdominal distension, pancreatitis, paralytic ileus, toxic megacolon); Hypersensitivity reactions (urticaria, pruritus, gum swelling, angioedema); CNS effects (drowsiness, restlessness, euphoria, depression, headache, numbness) Reactions from Atropine: Dry mouth, dysphagia, pupillary dilatation with loss of accommodation, flushed and dry skin, disturbances in cardiac rate and rhythm, difficulty in micturition, constipation Special Instructions Use with caution in patients with IBD, hepatic impairment Avoid in patients with jaundice, intestinal obstruction, antibiotic-associated colitis, enterotoxigenic diarrhea
Loperamide	Initial dose: 4 mg PO Followed by 2 mg PO after each unformed stool Max dose: 16 mg/day	Adverse Reactions GI effects (abdominal pain, nausea, constipation, rarely paralytic ileus); hypersensitivity reactions Special Instructions Use with caution in patients with hepatic impairment Do not use in patients with ileus, abdominal distension, acute IBD, antibiotic-associated colitis, or any other condition for which inhibition of peristalsis must be avoided
Intestinal Adsorbent
Dioctahedral smectite (Diosmectite)	9 g/day dissolved in liquid PO divided 8-12 hourly x 7 days	Adverse Reactions Rarely constipation May decrease the absorption of many drugs; avoid simultaneous oral therapy
¹Combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Antispasmodics

Drug	Dosage	Remarks
Belladonna Alkaloids
Atropine	0.6-1.2 mg PO at bedtime as a single dose or 0.4-0.6 mg IM/SC/IV 4-6 hourly	Adverse Reactions CV effects (tachycardia, transient bradycardia): CNS effects (delirium, agitation, amnesia); Ophthalmologic effects (photophobia, blurred vision); Other effects (pulmonary edema, urinary retention); Rarely, hypertensive crisis and seizures Potentially fatal: Asystole, MI, arrhythmia, respiratory depression, coma Special Instructions Use with caution in patients with brain damage, increased intraocular pressure, spastic paralysis, diarrhea, COPD, heart failure, hypertension and cardiac surgery Contraindicated in patients with myasthenia gravis, toxic megacolon, angle-closure glaucoma, 2nd- or 3rd-degree AV block
Hyoscine-N-butylbromide	10 mg PO 8 hourly May increase to 20 mg PO 6 hourly or 20-40 mg slow IV/IM few times a day Max dose: 100 mg/day	Adverse Reactions Urinary retention, tachycardia, allergic reactions Special Instructions Contraindicated in patients with myasthenia gravis and megacolon Avoid in patients with glaucoma, heart failure, thyrotoxicosis, difficulty in urinary process, fever and the elderly
Hyoscyamine	0.125-0.250 mg PO or sublingually 4 hourly Max dose: 1.5 mg/day or 0.25-0.5 mg IV/IM/SC injection 4 hourly	Adverse Reactions GI effects (dry mouth, nausea/vomiting, constipation, bloating); CNS effects (headache, nervousness, drowsiness, dizziness, insomnia, mental confusion/excitement); Ophthalmologic effects (blurred vision, mydriasis, cycloplegia, increased ocular tension); Other effects (urinary retention, tachycardia, palpitations, impotence, suppression of lactation, hypersensitivity reactions, decreased sweating) Special Instructions Use with caution in patients with autonomic neuropathy, hyperthyroidism, coronary heart disease (CHD), chronic heart failure (CHF), cardiac arrhythmias, hypertension, renal disease, hiatal hernia with reflux esophagitis Avoid in patients with glaucoma, obstructive uropathy, GIT disease, paralytic ileus, intestinal atony of elderly or debilitated patients, unstable CV status, severe ulcerative colitis (UC), toxic megacolon, myasthenia gravis
Papaverine Derivative
Drotaverine	40-80 mg PO 8 hourly	Adverse Reactions Nausea and vertigo Special Instructions Avoid in patients with severe liver, renal or cardiac insufficiency
Synthetic Anticholinergics
Chlordiazepoxide/Clidinium bromide	Chlordiazepoxide 5 mg/Clidinium bromide 2.5 mg per tab 1-2 tab PO 6-8 hourly	Adverse Reactions CNS effects (sedation, drowsiness, muscle weakness, ataxia. Less commonly: Slurred speech, vertigo, headache, confusion); urinary and GI disturbances. Symptoms decrease after continued use Paradoxical excitement can occur Reactions from Clidinium: Dry mouth, dysphagia, pupillary dilatation with loss of accommodation, flushed and dry skin, disturbances in cardiac rate and rhythm, difficulty in micturition, constipation Special Instructions Use with caution in patients with renal disease, hepatic disease, hypertension, CV disease, UC, hernia, reflux esophagitis; elderly and debilitated patients Contraindicated in cases of hypersensitivity, myasthenia gravis, glaucoma, obstructive uropathy, GI obstruction, paralytic ileus, unstable CV status, acute resp conditions, pregnancy and lactation May impair ability to drive or operate machinery
Dicycloverine hydrochloride (Dicyclomine)	10-20 mg PO 6-8 hourly Max dose: 160 mg/day or 10-20 mg IM 6 hourly x 1-2 days	Adverse Reactions CNS effects (dizziness, headache, insomnia); Other effects (GI disturbances, anorexia, decreased heart rate, rash) Special Instructions Use with caution in patients with cardiac disorders, renal and hepatic impairment Contraindicated in patients with GI obstruction, paralytic ileus, unstable CV status
Mebeverine hydrochloride	100 mg PO 6 hourly or 135 mg PO 8 hourly or 200 mg PO 12 hourly
Otilonium bromide	40 mg PO 8-12 hourly	Adverse Reactions CNS effects (headache, dizziness); GI effects (nausea/vomiting, epigastric pain, abdominal discomfort) Special Instructions Use with caution in patients with glaucoma, prostatic hypertrophy, pyloric stenosis
Propantheline bromide	15 mg PO 8 hourly and 30 mg PO at bedtime Max dose: 120 mg/day	Adverse Reactions GI effects (dry mouth, dysphagia, constipation): Other effects (pupillary dilatation with loss of accommodation, flushed and dry skin, disturbances in cardiac rate and rhythm, difficulty in micturition) Special Instructions Use with caution in the elderly, hepatic or renal impairment, hyperthyroidism, CHF, arrhythmias, hypertension, Avoid in patients with glaucoma, obstructive uropathy, obstructed GIT, paralytic ileus, intestinal atony, UC, toxic megacolon, myasthenia gravis, unstable CV status in acute hemorrhage
Other Drugs for Functional Bowel Disorders
Alverine citrate¹	60-120 mg PO 8 hourly	Adverse Reactions CNS effects (headache, dizziness); Other effects (nausea, itching, rash and hypersensitivity reactions) Special Instructions Contraindicated in patients with paralytic ileus
Peppermint oil¹	187-374 mg PO 8 hourly or 0.2-0.4 mL PO 8 hourly Max duration of treatment: 3 months	Adverse Reactions GI effects (heartburn, perianal irritation); CNS effect (headache); Dermatologic effects (contact dermatitis, erythema); muscle tremor Special Instructions Administer 0.5-1 hour before meals Use with caution when given with drugs that decrease hydrochloric acid in the stomach Avoid in patients with bile duct obstruction, gallbladder inflammation or liver damage
Pinaverium bromide	50-100 mg PO 8-12 hourly Max dose: 300 mg/day	Adverse Reactions Dyspepsia, skin rash Special Instructions Administer with a full glass of water with a meal or snack to minimize risk of esophageal irritation Avoid in patients with gastroesophageal reflux or hiatal hernia
¹Combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

GIT Regulators, Antiflatulents & Anti-inflammatories

Drug	Dosage	Remarks
Sodium butyrate (Na butyrate)	150 mg PO 12 hourly x at least 3 months	Special Instructions Should be taken with food Do not use as a substitute or alternative for a healthy balanced diet Do not give to patients with swallowing difficulties
Serotonin 5-HT₄ Receptor Agonist
Tegaserod	6 mg PO 12 hourly x 4-6 weeks	Adverse Reactions CV effects (hypotension, arrhythmia); GI effects (diarrhea, abdominal pain, nausea, flatulence); CNS effects (headache, dizziness, migraine, insomnia); Other effects (leg or back pain, arthropathy, ischemic colitis) Potentially fatal: MI, stroke Special Instructions Avoid in patients with severe renal or hepatic impairment, history of bowel obstruction or symptomatic gallbladder disease, patients with diarrhea Discontinue treatment if with inadequate symptom control after 4-6 weeks
Synthetic Anticholinergic
Trimebutine	100-200 mg PO 8 hourly	Adverse Reactions GI effects (constipation, diarrhea, dyspepsia); CNS effects (dizziness, sleepiness/drowsiness, headache); Other effects (urinary retention, slight deafness) Special Instructions Elderly, pregnancy, lactation

Laxatives, Purgatives

Drug	Available Strength	Dosage	Remarks
Bulk-producing Laxatives¹
Ispaghula husk (Plantago ovata seed shells, psyllium)	Capsule	5 cap PO 12 hourly	Adverse Reactions Large quantities may temporarily increase flatulence and abdominal distension; hypersensitivity reactions; intestinal/esophageal obstruction and fecal impaction especially if swallowed dry Special Instructions Avoid in patients with difficulty swallowing, those with pre-existing fecal impaction, intestinal obstruction or colonic atony
	Bulk powder	2-3 tsp in 250 mL of liquid PO 8-24 hourly
	Smooth texture or orange flavor bulk powder	1 1/2 tsp in 250 mL of liquid PO 8-24 hourly
	3.25 g/sachet, 3.5 g/sachet, 5 g/sachet, 6 g/sachet	1 sachet in ≥150 mL of liquid PO 8-24 hourly Max dose: 6 sachets/day
Polycarbophil	500 mg/tab	2 tab PO 6 hourly Max dose: 12 tab/day
Osmotic Laxatives
Lactitol	10 g/15 mL oral syrup	15-30 mL PO 24 hourly	Adverse Reactions GI effects (abdominal discomfort, flatulence, cramps, nausea/vomiting may occur) Prolonged use or excessive dose may cause diarrhea with loss of water and electrolytes Mg-containing products could cause hypermagnesemia Special Instructions Avoid in patients with intestinal obstruction; Lactulose should not be given to patients with galactosemia
Lactulose	10 g/15 mL oral syrup	Initial dose: 15-45 mL PO 24 hourly Maintenance dose: 15-30 mL PO 24 hourly
Macrogol 4000	10 g/sachet	1-2 sachets dissolved in liquid PO 24 hourly
Magnesium hydroxide [Mg (OH)₂, Milk of magnesia]	400 mg/5 mL oral suspension	30-60 mL PO 24 hourly at bedtime
	800 mg/5 mL oral suspension	10-20 mL PO 24 hourly at bedtime
	8 g/100 mL oral suspension	30-45 mL PO 24 hourly at bedtime or morning after waking
Sorbitol	70% oral solution	30-45 mL PO 24 hourly
Other Laxative
Lubiprostone	Women ≥18 years old: 8 mcg PO 12 hourly		Adverse Reactions GI effects (abdominal distention/pain, diarrhea, flatulence, nausea/vomiting); CNS effects (headache, dizziness); Other effects (fatigue, dyspnea, peripheral edema) Special Instructions Take with food and water Contraindicated in patients with history of mechanical GI obstruction Avoid in patients with severe diarrhea
¹Various combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Other Antibiotics

Drug

Dosage

Remarks

Rifaximin

550 mg PO 8 hourly x 14 days
or
800-1,200 mg/day PO divided 8-12 hourly x 7-14 days

Adverse Reactions

GI effects (abdominal pain, bloating, constipation, diarrhea, urgency to evacuate feces, nausea/vomiting, involuntary and painful or ineffective straining); CNS effects (headache, dizziness)

Special Instructions

Use with caution in patients taking estrogen contraceptives or with severe hepatic impairment
Contraindicated in patients with infectious/traveler’s diarrhea with fever and/or bloody stools; hypersensitivity to Rifampicin/Rifabutin

Other Gastrointestinal Drugs

Drug	Dosage	Remarks
Guanylate Cyclase-C Receptor Agonist
Linaclotide	Adult with IBS-C: 290 mcg PO 24 hourly	Adverse Reactions GI effects (diarrhea, abdominal pain, flatulence, abdominal distention); Other effects (viral gastroenteritis, dizziness) Special Instructions Should be taken on an empty stomach, at least 30 minutes before meals Discontinue in prolonged diarrhea (>1 week) or severe diarrhea until resolved Contraindicated in patients with chronic intestinal tract inflammatory conditions (eg Crohn’s disease and UC), elderly >65 years old, children <18 years old, pregnancy and lactation Monitor electrolytes in patients prone to disturbance of water or electrolyte balance (eg elderly, CV diseases, diabetes, hypertension)
Serotonin 5-HT₃ Receptor Antagonists
Alosetron hydrochloride	Women with IBS-D: 0.5 mg PO 12 hourly x 4 weeks If drug is well tolerated but symptoms not well controlled after 4 weeks, may increase to 1 mg PO 12 hourly x 4 weeks Max dose: 2 mg/day	Adverse Reactions Frequently constipation; less commonly GI pain/discomfort Serious complications of constipation including obstruction, ileus, impaction, toxic megacolon and secondary bowel ischemia have been reported along with rare cases of perforation Special Instructions Stop treatment if constipation develops during the initial 4 weeks until constipation resolves then re-initiate treatment with once daily dosing; discontinue treatment permanently if constipation develops with once daily dosing Discontinue therapy if IBS symptoms are not well-controlled after 4 weeks of 1 mg PO 12 hourly dose Do not use in patients with constipation; in patients with a history of severe/chronic constipation, intestinal obstruction, stricture, toxic megacolon, GI perforation and/or adhesions, ischemic colitis, impaired intestinal circulation, thrombophlebitis, hypercoagulable state, IBD or diverticulitis Do not use with CYP1A2 inhibitors, especially Fluvoxamine
Ramosetron	Men with IBS-D: 5 mcg PO 24 hourly Max dose: 10 mcg/day	Adverse Reactions GI effects (constipation, ischemic colitis, abdominal distention/pain, increased liver enzymes); shock and anaphylactoid symptoms, anemia, palpitations, back pain, headache, rash, prostatitis Special Instructions Rule out large intestinal carcinoma, IBD, and enteritis infection before therapy Use with caution in patients with history of abdominal surgery Do not use in female patients, patients with a history of chronic constipation or IBS-C

Disclaimer

All dosage recommendations are for non-pregnant and non-breastfeeding women, and non-elderly adults with normal renal and hepatic function unless otherwise stated.
Not all products are available or approved for above use in all countries.
Products listed in the Drug Summary are based on indications stated in the locally approved product monographs.
Please refer to local product monographs in Related MIMS Drugs for country-specific prescribing information.

Irritable Bowel Syndrome Drug Summary