Diarrhea in Adults - Infectious Drug Summary

Last updated: 23 March 2026
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Aminoglycoside

Drug Dosage Remarks
Kanamycin 1-2 g IM injection 24 hourly Adverse Reactions
  • Ototoxicity, nephrotoxicity, GI upsets
  • Rarely, shock, vitamin K and vitamin B deficiency
Special Instructions
  • Use with caution in patients with poor oral or parenteral nutrition, renal impairment, myasthenia gravis; elderly
  • Use with blood substitutes or diuretics may increase toxicity

Antibacterial Combination

Drug Dosage Remarks
Co-trimoxazole
(Sulfamethoxazole [SMZ] and  Trimethoprim
[TM]) 		800 mg SMZ/160 mg TM PO 12 hourly for 3 days Adverse Reactions
  • GI effects (nausea/vomiting, anorexia, diarrhea); Dermatologic effects (rash, pruritus, photosensitivity); Hypersensitivity reactions (rash, Stevens-Johnson syndrome); GU effect (crystallization in the urine)
Special Instructions
  • Maintain adequate fluid intake
  • Contraindicated in patients allergic to sulfonamides
  • Use with extreme caution or not at all in patients with hematological disorders

Antidiarrheals

Drug Dosage Remarks
Antidiarrheal Microorganisms
Bacillus clausii 2 billion spores/5 mL oral suspension
2-3 vials PO 24 hourly at 3–4-hour intervals		 Special Instructions
  • Given in interval between antibiotic doses
Bifidobacterium lactis1 BB-12 1 g PO 24 hourly Special Instructions
  • Avoid in patients with allergy to milk and dairy products
  • May have possible reduced effect with antibiotics
Lactobacillus acidophilus1 First day: 4 cap PO for first dose then 2 cap PO for second dose
Following days: 2 cap PO 12 hourly or
First day: 2 sachets PO for first dose then 1 sachet PO for second dose
Following days: 1 sachet PO 12 hourly 		Special Instructions
  • May be taken with or without food
  • Contents of capsule or sachet can be mixed with water
Lactobacillus reuteri 450-900 mg PO 24 hourly Special Instructions
  • Should be taken with food
Lyophilized Saccharomyces boulardii CNCM I-745 250-500 mg PO 12-24 hourly
or 282.5-565 mg PO 12 hourly
Prevention of traveler’s diarrhea: 250 mg PO 12-24 hourly
Must be taken 5 days before travel 		Adverse Reactions
  • Dermatologic effects (rash, urticaria, pruritus); Other effects (flatulence, angioedema, shock)
Special Instructions
  • Use with caution in patients with diarrhea of >2 days, pregnancy, lactation
  • Contraindicated in patients with allergies to yeast and immunocompromised
Antipropulsives
Diphenoxylate2 Initial dose: 5-10 mg PO
Followed by 2.5-5 mg PO 6-8 hourly 		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)
Special Instructions
  • Avoid in patients with jaundice, intestinal obstruction, antibiotic-associated colitis, enterotoxigenic diarrhea
  • Use with caution in patients with IBD and hepatic impairment
Loperamide3 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
  • 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
  • Use with caution in patients with hepatic impairment
Intestinal Adsorbents
Attapulgite4 Initial dose: 1,200 mg PO after each bowel movement
Max dose: 7,200 mg/day 		Adverse Reactions
  • GI effects (constipation, fecal impaction if given in large doses)
Special Instructions
  • Contraindicated in patients with severe renal or hepatic failure
  • Avoid in patients with chronic or invasive infectious diarrhea
Bismuth subsalicylate 524 mg PO every 30 minutes -1 hour as required
Max dose: 8 doses/day
or
1,048 mg PO 12 hourly
Dosage may be repeated 1 hourly if needed
Max dose: 4 doses/day 		Adverse Reactions
  • Long-term use may produce tinnitus; allergic reactions in salicylate-sensitive patients; black discoloration of the tongue/black stools from non-absorbable Bismuth salts
Special Instructions
  • Use with caution in patients with gout, renal insufficiency and those taking anticoagulants, Probenecid, Methotrexate, Aspirin-containing drugs
  • Brushing the teeth and tongue, rinsing mouth with water after each dose may help prevent tongue discoloration
Charcoal (Activated charcoal)4 500 mg-1 g PO 6-8 hourly Adverse Reactions
  • Black feces, may decrease GI motility
Special Instructions
  • May decrease the absorption of many drugs; avoid simultaneous oral therapy
Dioctahedral smectite (Diosmectite) 9-12 g/day PO in 2-4 divided doses Adverse Reactions
  • GI effects (constipation, flatulence, vomiting); Other effects (hypersensitivity reactions eg urticaria, rashes, pruritus, angioedema)
Special Instructions
  • Contraindicated in patients with fructose intolerance
  • Avoid in patients with history of severe chronic constipation, pregnancy
  • Should be taken alone and not with other drugs as it affects absorption of these substances
Kaolin4 Up to 24 g PO 24 hourly in divided doses Adverse Reactions
  • GI effect (rarely severe constipation)
Special Instructions
  • Contraindicated in patients with spastic bowel condition and intestinal obstruction
Other Antidiarrheals
Iodochlorhydroxyquinoline/Phthalylsulphathiazole Iodochlorhydroxyquinoline 0.25 mg/Phthalylsulphathiazole 0.5 mg per tab
1-2 tab PO 6 hourly for <10 days 		Adverse Reactions
  • GI effects (nausea/vomiting, abdominal discomforts, hepatotoxicity); Other effects (CNS effect, headache, acute pulmonary reaction, hemolytic anemia, skin rash)
Special Instructions
  • Use with caution in patients with kidney or liver disease, G6PD deficiency
  • Contraindicated in patients with impaired kidney or liver function, hyperthyroidism, iodine intolerance
Racecadotril 100 mg PO anytime of the day, then 100 mg PO 8 hourly until 2 normal stools are recorded
Max duration: 7 days 		Adverse Reactions
  • GI effects (nausea, constipation); CNS effects (headache, drowsiness)
Special Instructions
  • Ensure adequate hydration
  • Contraindicated in patients with bloody/purulent stool and/or fever, prolonged uncontrolled vomiting, pregnancy, lactation, fructose intolerance, sucrase-isomaltase deficiency, glucose-galactose malabsorption
1Various combination products for Bifidobacterium sp or L acidophilus are available. Please see the latest MIMS for specific formulations and prescribing information. 
2Combinations with Atropine are available. Please see the latest MIMS for specific formulations and prescribing information. 
3Combinations with Simeticone are available. Please see the latest MIMS for specific formulations and prescribing information.
4Various combinations of Attapulgite, Activated charcoal or Kaolin are available. Please see the latest MIMS for specific formulations and prescribing information.

Cephalosporin

Drug Dosage Remarks
Third Generation
Ceftriaxone Salmonella sp: 1-2 g IV 24 hourly for 3-14 days
Shigella sp:
1-2 g IV 24 hourly for 5 days 		Adverse Reactions
  • Hypersensitivity reactions (urticaria, pruritus, rash, anaphylaxis); GI effects (diarrhea, nausea/vomiting, rarely antibiotic-associated diarrhea/colitis); Other effect (candidal infections)
  • High doses may be associated with CNS effects (encephalopathy, convulsions)
  • PT, APTT and/or hypoprothrombinemia (with or without bleeding) have been reported and occur most frequently with NMTT side chain-containing cephalosporins
Special Instructions
  • May be taken with food to decrease gastric distress
  • Use with caution in patients allergic to Penicillin as there may be 10% chance of cross-sensitivity and with renal impairment

Electrolytes*

Drug Dosage Remarks
Potassium chloride (KCl) Severe deficiencies:
1,800-3,600 mg/day PO in divided doses 		Adverse Reactions
  • GI effects (nausea/vomiting, abdominal pain, diarrhea); Other effect (hyperkalemia)
Special Instructions
  • Should be taken with food
  • Monitor serum electrolytes, ECG and clinical status particularly in the presence of cardiac or renal disease and acidosis
  • Avoid in patients using K-sparing diuretics
Oral Rehydration Salt Formulation
Sodium chloride (NaCl)/Potassium chloride (KCl)/Sodium citrate/Anhydrous glucose Individualized dosage
Adjust total daily intake to meet individual needs based on thirst and response to therapy 		Adverse Reactions
  • Vomiting, hypernatremia, overhydration
Special Instructions
  • Contraindicated in patients with ≥10% dehydration and continued vomiting
  • Avoid in patients with GI obstruction, oliguric or anuric renal failure or when parenteral rehydration therapy is indicated
*Various electrolyte preparations for dehydration are available. Please see the latest MIMS for specific formulations and prescribing information.

Macrolide

Drug Dosage Remarks
Azithromycin Cholera: 1 g PO x 1 dose
Traveler’s diarrhea:
500 mg PO 24 hourly for 3 days or
1 g PO x 1 dose
Campylobacter sp:
500 mg PO 24 hourly for 3 days or
1 g PO x 1 dose
Shigella sp: 500 mg PO 24 hourly for 3 days 		Adverse Reactions
  • GI effects (nausea/vomiting, abdominal discomfort, diarrhea, other GI disturbances, antibiotic-associated diarrhea/colitis); Other effect (candidal infections)
  • Hypersensitivity reactions are uncommon (urticaria, pruritus, rash, rarely anaphylaxis); rarely cardiotoxicity, hepatotoxicity; dose-related tinnitus/hearing loss have occurred with some macrolides
  • Azithromycin and Clarithromycin tend to cause less GI disturbances than Erythromycin
Special Instructions
  • May take with food to decrease gastric distress
  • Use with caution in patients with hepatic or renal dysfunction

Other Antibiotics

Drug Dosage Remarks
Colistin sulfate 1.5-3 MIU PO 8 hourly Special Instructions
  • Use with caution in patients with pre-existing renal impairment, neuromuscular transmission disorder
  • Contraindicated in patients with hypersensitivity, anuria, porphyria, myasthenia gravis
Furazolidone1 100 mg PO 6 hourly for 2-5 days Adverse Reactions
  • GI effects (nausea/vomiting); CNS effects (dizziness, drowsiness, headache); Other effects (hypersensitivity, hypoglycemia, orthostatic hypotension, malaise, rashes, fever, arthralgia, brown urine, hemolytic anemia)
Special Instructions
  • Use with caution in patients with G6PD deficiency, history of alcoholism or frequent alcohol use, pregnancy and lactation
  • Contraindicated in patients with prior hypersensitivity to the drug
  • Avoid food and beverage with tryptophan or tyramine (including beer and wine), cheese, yoghurt
  • Avoid excessive amounts of caffeine and chocolate
  • Avoid concomitant administration with MAOIs
Nifuroxazide 800-1,600 mg/day PO in 2-4 divided doses for ≤7 days Adverse Reactions
  • Dermatologic effects (rash, urticaria, allergic reaction); Other effects (anaphylactic shock, Quincke’s edema)
Special Instructions
  • Use with caution in patients with liver disease, epilepsy, alcoholism, on low-salt diet, pregnancy, lactation
  • Contraindicated in patients with bloody/mucoid stool and fever, allergic to nitrofurantoin derivatives, with intolerance to lactose, sucrase-isomaltase deficiency
Rifaximin 200 mg PO 8 hourly for 3 days
Max dose:
800 mg/day for 3 days 		Adverse Reactions
  • GI effects (nausea/vomiting, urgency to pass stools, abdominal pain, bloating and distention, flatulence, constipation); CNS effects (dizziness, headache); Other effect (pyrexia)
Special Instructions
  • Contraindicated in patients allergic to Rifampicin or Rifabutin, diarrhea with fever and/or blood in stools, pregnancy, lactation
1Various combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Penicillins

Drug Dosage Remarks
Amoxicillin/clavulanic acid
(Amoxicillin/clavulanate,
Co-amoxiclav) 		250 mg/125 mg or
500 mg/125 mg PO 8 hourly 		Adverse Reactions
  • Hypersensitivity reactions (rash); GI effects (diarrhea, nausea/vomiting, hepatitis, pseudomembranous colitis); Other effects (erythema multiforme, exfoliative dermatitis, toxic epidermal necrolysis)
Special Instructions
  • Avoid in patients with Penicillin allergy
  • Use with caution in patients with renal impairment
Ampicillin 500 mg PO/IM/IV 6 hourly Adverse Reactions
  • Skin rashes which are generally urticarial or maculopapular
Special Instructions
  • Contraindicated in patients with hypersensitivity to the drug
  • Discontinue use if rash occurs
  • Use with caution in patients with infectious mononucleosis, lymphatic leukemia, HIV infection, pregnancy and lactation

Quinolones

Drug Dosage Remarks
Ciprofloxacin 500 mg PO 12 hourly for 3-7 days or
200-400 mg IV infusion 12 hourly over 30-60 minutes for 1-5 days
Cholera:
500 mg PO 12 hourly for 3 days or 1 g PO x 1 dose or
400 mg IV infusion 12 hourly for 3 days 		Adverse Reactions
  • GI effects (nausea/vomiting, diarrhea, abdominal pain, dyspepsia, rarely antibiotic-associated diarrhea/colitis); CNS effects (headache, dizziness, sleep disorders, restlessness, drowsiness); Dermatologic effects (rash, pruritus, photosensitivity); Hypersensitivity reactions (rash, Stevens-Johnson syndrome)
  • Some quinolones have the potential to prolong the QT interval
Special Instructions
  • Administer at least 2 hours before or 3-4 hours after Al- or Mg-containing antacids, dietary supplements containing Zn, Ca or Fe or buffered Didanosine preparations
  • Avoid exposure to strong sunlight or tanning beds
  • Use with caution in patients with epilepsy or history of CNS disorders, impaired renal or hepatic function and G6PD deficiency
Levofloxacin 250-500 mg PO 12-24 hourly for 7-14 days
Nalidixic acid Shigellosis: 1 g PO 6 hourly for 5-7 days
Norfloxacin 400 mg PO 12 hourly for 5 days
Ofloxacin 200 mg PO 12 hourly or 400 mg PO 12-24 hourly for 1-3 days
Continue daily dosing for up to 3 days if symptoms are not resolved after 24 hours with single dose or
300-600 mg/day PO in 2-3 divided doses
Pefloxacin 400 mg PO 12 hourly
Prulifloxacin 200-300 mg PO 12 hourly

Tetracyclines

Drug Dosage Remarks
Doxycycline Cholera: 300 mg PO x 1 dose as prophylaxis or 100 mg PO 12 hourly on day 1 then 50 mg PO 12 hourly or 100 mg PO 24 hourly
Traveler's diarrhea: 200 mg PO on first day of travel as single dose, followed by 100 mg PO 24 hourly
Yersinia sp: 100 mg IV 12 hourly 		Adverse Reactions
  • GI effects (nausea/vomiting, diarrhea, antibiotic-associated diarrhea/colitis, dysphagia, esophageal ulceration when taken with an insufficient amount of liquid); Dermatologic effect (photosensitivity); Other effects (candidal infections, discoloration of teeth, interference with bone growth in pregnant women)
  • Hypersensitivity reactions have occurred
Special Instructions
  • Lymecycline and Tetracycline: Taken on an empty stomach
    • Take with plenty of fluid while sitting or standing and well before retiring to bed
  • Avoid long exposure to sunlight or tanning beds
  • Avoid in pregnant women, in patients with systemic lupus erythematosus (SLE)
  • Use with caution in patients with renal or hepatic impairment
Lymecycline Cholera: 300 mg PO 12 hourly
Minocycline Cholera: 200 mg PO initially then 100 mg PO 12 hourly
Tetracycline Mild to moderate infections:
500 mg PO 12 hourly or 250 mg PO 6 hourly
Severe infections: 500 mg PO 6 hourly
Cholera: 500 mg PO 6 hourly for 3 days

Vaccines, Antisera & Immunologicals

Drug Dosage Remarks
Bivalent killed whole cells of
Vibrio cholerae O1 and O139 strains 		Cholera: 2 doses of 1.5 mL PO given at 2-week interval Adverse Reactions
  • GI effects (abdominal pain, loose stools, nausea/vomiting, dry mouth); Dermatologic effects (rash, pruritus); Other effects (fever, weakness, cough, vertigo)
Special Instructions
  • Transient increases in viral load in immunization of HIV-infected patients
  • Contraindicated in patients with acute illness or hypersensitivity to formaldehyde
  • Killed bivalent whole cells of V cholerae O1 and O139: Not recommended during pregnancy and lactation
  • Not be used as replacement for cholera therapy
Monovalent killed Vibrio
cholerae O1 Inaba and Ogawa, classic and El Tor strains, cholera toxin B 		Cholera: 2 doses of 3 mL PO administered at 1- to 6-week interval, single booster dose after 2 years
ETEC: 2 doses of 3 mL PO administered at 1- to 6-week interval
Live attenuated 
Vibrio cholerae strain CVD 103-HgR 		Cholera: Single dose of
100 mL PO for a minimum of 10 days prior potential exposure to cholera 		Adverse Reactions
  • GI effects (abdominal pain, loose stools, nausea/vomiting); Other effects (tiredness, headache, lack of appetite)
Special Instructions
  • Safety and effectiveness have not been established in immunocompromised individuals; use with caution when considering to administer to individuals with immunocompromised close contacts
  • Contraindicated in patients with severe allergic reaction to any of its ingredients or to a prior dose of any cholera vaccine
  • Avoid concomitant administration with systemic antibiotics; do not administer to patients who have received oral or parenteral antibiotics within 14 days prior to vaccination
  • Maternal use/breastfeeding is not expected to result in fetal/child exposure to the drug

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.  

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