Gastroenteritis - Bacterial Drug Summary

Last updated: 23 April 2026
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Antibacterial Combination

Drug Dosage Remarks
Co-trimoxazole
(Sulfamethoxazole [SMZ] and
Trimethoprim [TMZ])		 8-12 mg/kg/day PO divided 12 hourly based on TM Adverse Reactions
  • GI effects (nausea/vomiting, anorexia, diarrhea, glossitis, stomatitis, rarely antibiotic-associated diarrhea/colitis); Dermatologic effects (rash, pruritus, photosensitivity); Hypersensitivity reactions can range from mild (eg rash) to severe/life-threatening (eg Stevens-Johnson syndrome, toxic epidermal necrolysis); Urogenital effect (crystallization in the urine)
  • Rarely hematologic effects which may be more common if given for long periods or with high doses; rarely hepatic effects, renal effects; aseptic meningitis has occurred
Special Instructions
  • Maintain adequate fluid intake
  • Contraindicated in patients <2 months of age and patients with sulfonamide allergy
  • Use with extreme caution or not at all in patients with hematological disorders especially megaloblastic anemia due to folic acid deficiency
  • Use with caution in patients with renal impairment or severe hepatic dysfunction, folate deficiency (may consider administration of Calcium folinate), glucose-6-phosphate dehydrogenase deficiency

Antidiarrheals

Drug Dosage Remarks
Antidiarrheal Microorganisms
Bacillus clausii 2-3 vials PO 24 hourly Special Instructions
  • Given in interval between antibiotic doses
Lactobacillus spp
(L reuteri, L acidophilus, L rhamnosus, L sporogenes)		 450 mg PO 24 hourly Special Instructions
  • Should be taken with food
Lyophilized
Saccharomyces boulardii		 250 mg PO 12-24 hourly
Prevention of traveler’s diarrhea: Must be taken 5 days before travel		 Adverse Reactions
  • Dermatologic effects (rash, urticaria, pruritus); Other effects (flatulence, angioedema)
Special Instructions
  • Contraindicated in patients with allergies to yeast and immunocompromised
  • Use with caution in patients with diarrhea of >2 days
Antipropulsive
Loperamide1 Initial dose:
6-8 years old: 2 mg PO, then 1 mg PO after each subsequent loose stool
9-11 years old: 2 mg PO, then 1 mg PO after each subsequent loose stool
≥12 years old: 4 mg PO, then 2 mg PO after each subsequent loose stool
Max dose:
2-5 years old: 3 mg/day
6-8 years old: 4 mg/day
9-12 years old: 6 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 inflammatory bowel disease, 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
Bismuth salicylate 3-6 years old: 87 mg PO every 30 minutes -1 hour as required
6-9 years old: 175 mg PO every 30 minutes -1 hour as required
9-12 years old: 262 mg PO every 30 minutes -1 hour as required
Max dose: 8 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
Dioctahedral smectite ≥2 years old: 6-9 g/day PO in 2-3 divided doses Adverse Reactions
  • GI effect (rarely constipation)
Special Instructions
  • Should be taken alone and not with other drugs as it affects absorption of these substances
Other Antidiarrheal
Racecadotril 1.5 mg/kg PO 8 hourly
Max dose: 6 mg/kg/day
≥3-9 months old; <9 kg: 10 mg PO 8 hourly
9-30 months old; 9-13 kg: 20 mg PO 8 hourly
30 months -9 years old; 13-27 kg: 30 mg PO 8 hourly
>9 years old; >27 kg: 60 mg PO 8 hourly
Max duration: 7 days
To be given in combination with ORS		 Adverse Reactions
  • GI effects (nausea, constipation, tongue edema, lip edema); Respiratory effect (tonsillitis); Dermatologic effects (rash, erythema, prurigo, pruritus); Other effects (headache, drowsiness, angioedema, urticaria, eyelid edema, face edema)
Special Instructions
  • Ensure adequate hydration
  • Contraindicated in patients with fructose intolerance, glucose-galactose malabsorption syndrome, or sucrose-isomaltase insufficiency
  • Use with caution in patients with bloody/purulent stool and/or fever, prolonged uncontrolled vomiting, diarrhea
Other Intestinal Anti-infective
Nifuroxazide Infant <6 months old: 250 mg PO 12 hourly
Children and infant >6 months old: 250 mg PO 8 hourly
Max duration: 7 days
>15 years old: 200 mg PO 6 hourly
Max duration: 7 days		 Adverse Reactions
  • GI effects (abdominal pain, diarrhea, green pigment on tongue, feces and urine); Other effects (allergic reactions, reduction of normal microbial flora, cerebral disturbances)
Special Instructions
  • Ensure adequate hydration
  • Contraindicated in patients with bloody or mucoid stools, fever, vomiting
  • Use with caution in patients with neurological disorder
Zinc-containing Preparations
Zinc
(Zinc sulphate monohydrate, Zinc sulfate)		 <6 months old: 10 mg PO 24 hourly x 10 days
>6 months -5 years old: 20 mg PO 24 hourly x 10 days		 Adverse Reactions
  • GI effects (nausea/vomiting, bitter taste, mouth irritation)
Special Instructions
  • Take at least 1 hour before or 2 hours after meals
  • May be taken with meals to reduce GI discomfort
  • Use with caution in patients at risk for renal failure
1Combination with Simeticone (Simethicone) is available. Please see the latest MIMS for specific formulations and prescribing information.

Cephalosporins

Drug Dosage Remarks
Third Generation
Cefixime >6 months old: 1.5-3 mg/kg PO 12 hourly
Severe infections: 6 mg/kg PO 12 hourly		 Adverse Reactions
  • Hypersensitivity reactions (urticaria, pruritus, rash, severe reactions eg anaphylaxis can occur); GI effects (diarrhea, nausea/vomiting, rarely antibiotic-associated diarrhea/colitis); Other effects (candidal infections, injection site inflammation)
  • High doses may be associated with CNS effects (encephalopathy, convulsions); Rarely hepatic, renal and hematologic effects have occurred
  • Prolonged prothrombin time (PT), prolonged activated partial thromboplastin time (APTT), and/or hypoprothrombinemia (with or without bleeding) have been reported and occurs most frequently with N-methylthiotetrazole (NMTT) side chain-containing cephalosporins
Special Instructions
  • May be taken with food to decrease gastric distress
  • Ceftriaxone is contraindicated in hyperbilirubinemic neonates
  • Avoid simultaneous administration of Ceftriaxone with IV Ca-containing solution
  • Use suspension containing sodium benzoate with caution in neonates as this has been associated with gasping syndrome
  • Use with caution in patients allergic to Penicillin, there may be 10% chance of cross sensitivity; and patients with renal impairment and GI disease especially with history of colitis
Cefoperazone 50-200 mg/kg/day IM/IV divided 12 hourly
Cefotaxime Neonates <7 days:
1.2-2 kg: 100 mg/kg/day IM/IV divided 12 hourly
>2 kg: 100-150 mg/kg/day IM/IV divided 8-12 hourly
Neonates >7 days:
1.2-2 kg: 150 mg/kg/day IM/IV divided 8 hourly
>2 kg: 150-200 mg/kg/day IM/IV divided 6-8 hourly
Infants and children:
100-200 mg/kg/day IM/IV divided 6-8 hourly
Ceftazidime 0-2 months old: 25-60 mg/kg/day IM/IV divided 12 hourly
>2 months old: 30-100 mg/kg/day IM/IV divided 8-12 hourly
Max dose: 6 g/day IM/IV divided 8 hourly
Ceftibuten 9 mg/kg PO 24 hourly or 4.5 mg/kg PO 12 hourly
Max dose: 400 mg/day
Ceftriaxone Infant ≤2 weeks old: 20-50 mg/kg IM/IV 24 hourly
Max dose: 50 mg/kg
2 weeks-12 years old: 20-80 mg/kg IM/IV 24 hourly
>12 yr: 1,000-2,000 mg IM/IV 24 hourly
Fourth Generation
Cefepime >2 months old and ≤40 kg: 50 mg/kg IM/IV 8-12 hourly

Electrolytes*

Drug Dosage Remarks
Calcium chloride/
Glucose/Sodium bicarbonate/Sodium chloride		 Dissolve contents of 1 sachet in 200 mL or 1 L water -
Sodium chloride/Trisodium citrate/Potassium chloride/Glucose (NaCl/KCl/Trisodium citrate/Glucose anhydrous,Sodium chloride/Sodium citrate/Potassium chloride/Glucose) <2 years old: 1 sachet (5.125 g) PO for the first 2 hours, then up to 8 hourly
2-5 years old: 1 sachet (5.125 g) PO 3x for the first 2 hours, then up to 4 hourly
>5 years old: 1 sachet (5.125 g) PO 4x for the first 2 hours, then up to 3 hourly
or
Infant: 1-1.5x the usual feeding volume
Children: 200 mL PO for every loose motion		 Adverse Reactions
  • Hypernatremia, Na and water retention, nausea/vomiting
Special Instructions
  • Dissolve 1 sachet in 250 mL water
  • Use in caution in patients with renal impairment, severe dehydration, severe and prolonged diarrhea, glucose malabsorption, vomiting, inability to drink
Sodium/Potassium/Total carbohydrates/Sugar Drink 4 packs or dissolve 5 sachets in 1 L of water Special Instructions
  • Used for prevention and not as treatment for acute diarrhea in children
*Various combinations are available. Please see the latest MIMS for specific formulations and prescribing information.

Macrolides

Drug Dosage Remarks
Erythromycin 30-50 mg/kg/day PO divided 6-12 hourly Adverse Reactions
  • GI effects (nausea/vomiting, abdominal discomfort, diarrhea and other GI disturbances, antibiotic-associated diarrhea/colitis, stomatitis, infantile hypertrophic pyloric stenosis); Other effects (candidal infections, headache)
  • Hypersensitivity reactions are uncommon (urticaria, pruritus, rash, rarely anaphylaxis); Rarely cardiotoxicity, hepatotoxicity; Dose-related tinnitus/hearing loss have occurred with some macrolides
  • Azithromycin tends to cause less GI disturbances than Erythromycin
Special Instructions
  • May take with food to decrease gastric distress
  • Use with caution in patients with hepatic dysfunction
Advanced Macrolide
Azithromycin 10 mg/kg PO 24 hourly x 3 days
or
10 mg/kg PO 24 hourly x 1 day followed by 5 mg/kg PO 24 hourly x 4 days

Other Antibiotics

Drug Dosage Remarks
Rifaximin >12 years old: 200 mg PO 8 hourly x 3 days
or
400 mg PO 12 hourly x 3 days		 Adverse Reactions
  • CNS effects (dizziness, headache, nausea/vomiting); GI effects (pseudomembranous colitis, abdominal pain, bloating, constipation, diarrhea, urgency to evacuate feces, involuntary and painful/ineffective straining); Other effects (fever, overgrowth of non-susceptible organisms)
Special Instructions
  • Contraindicated in patients with infectious/traveler’s diarrhea with fever and/or bloody stools, and children <12 years old

Penicillins

Drug Dosage Remarks
Aminopenicillins with or without Beta-lactamase Inhibitors
Amoxicillin (Amoxycillin) 40-50 mg/kg/day PO divided 8 hourly
High-dose: 80-90 mg/kg/day		 Adverse Reactions
  • Hypersensitivity reactions (rash, urticaria, pruritus, severe reactions [eg anaphylaxis] can occur); GI effects (diarrhea, nausea/vomiting, rarely antibiotic-associated diarrhea/colitis); Other effect (candidal infections)
  • Rarely hematologic, renal and hepatic effects; high doses may be associated with CNS effects (encephalopathy, convulsions)
Special Instructions
  • Avoid in patients with Penicillin allergy
  • Use with caution in patients with renal impairment
Amoxicillin/clavulanic acid
(Co-amoxiclav, Amoxicillin/clavulanate)		 <3 months old: 30 mg/kg/day PO divided 12 hourly
≥3 months old: 25-50 mg/kg/day PO divided 8 hourly based on Amoxicillin or
Neonates: 25-30 mg/kg IV 8-12 hourly
≥3 months old: 25-30 mg/kg IV 6-8 hourly
Ampicillin 50-100 mg/kg/day PO divided 6 hourly or
100-200 mg/kg/day IM/IV divided 6 hourly
Ampicillin/sulbactam
(Sultamicillin [Ampicillin and Sulbactam], Sultamicillin: Pro-drug of Ampicillin/sulbactam, the 2 drugs are linked chemically with a double ester)		 <30 kg: 25-50 mg/kg/day PO divided 12 hourly based on Ampicillin or
150-300 mg/kg/day IM/IV divided 6-8 hourly

Quinolones

Drug Dosage Remarks
Ciprofloxacin 4-8 mg/kg IV 12 hourly Adverse Reactions
  • Hematologic effects (hemolytic anemia, agranulocytosis); CNS effects (headache, dizziness, restlessness, drowsiness, insomnia, nightmares and other sensory disturbances); GI effects (nausea/vomiting, diarrhea, abdominal pain, dyspepsia); Hepatic effects (elevated liver enzyme values, jaundice, hepatitis); Dermatologic effects (rash, pruritus, hypersensitivity-type reactions); GU effects (transient increase in serum creatinine or BUN, occasionally acute renal failure, interstitial nephritis, crystalluria); Other effects (myalgia, sweating, pain, irritation, anaphylaxis)
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
  • Use with caution in patients with epilepsy or history of CNS disorders, with or at risk for aortic aneurysm (eg patients with peripheral atherosclerotic vascular disease, hypertension, Marfan and Ehlers-Danlos syndrome)
Levofloxacin 250-500 mg PO 12-24 hourly x 10-14 days
Norfloxacin 400 mg PO 12 hourly x 5 days
Ofloxacin 200-300 mg PO 12 hourly x 5-7 days

Supplements & Adjuvant Therapy

Drug Dosage Remarks
Bovine colostrum ≥12 months old: 1 sachet (7 g) PO 24 hourly x 3 days Special Instructions
  • Mix the contents of 1 packet with 30 mL water in a cup
  • Use with caution in patients with allergy to milk and/or egg
Lactobacillus spp (L casei, L acidophilus, L rhamnosus, L bulgaricus)/Bifidobacterium spp (B breve, B infantis)/Streptococcus thermophilus1 1 sachet (1 g) PO 24 hourly x 4-7 days Special Instructions
  • Contents of the sachet may be added to food/water/milk/juice
  • Use with caution in patients with allergy to fish, soya or milk
1Various combination products are available. Please see the latest MIMS for specific formulations and prescribing information.

Tetracyclines

Drug Dosage Remarks
Doxycycline >8 years old and ≤45 kg: 4.4 mg/kg/day PO divided 12 hourly
Followed by 2.2 mg/kg/day PO divided 12 hourly		 Adverse Reactions
  • GI effects (nausea/vomiting, diarrhea, antibiotic-associated diarrhea/colitis has occurred, discoloration of teeth, dysphagia, esophageal ulceration has occurred when taken with an insufficient amount of liquid); Other effects (candidal infections, interference with skeletal development and bone growth, photosensitivity)
  • Rarely renal dysfunction, hepatotoxicity, hematologic effects, intracranial pressure with headache and visual disturbances; Hypersensitivity reactions have occurred
Special Instructions
  • Avoid long exposure to sunlight or tanning beds
  • Take with plenty of fluid while sitting or standing and before retiring to bed
  • Use with caution in renal or hepatic impairment
Tetracycline >8 years old: 25-50 mg/kg/day PO divided 6 hourly

Vaccines, Antisera & Immunologicals

Drug Dosage Remarks
Killed bivalent whole cells of Vibrio cholerae O1 and O139
(Vaccine, cholera)		 >1 year old: 2 doses of 1.5 mL PO given at 2-week interval Adverse Reactions
  • GI effects (abdominal pain, loose stools, nausea/vomiting, dry mouth); Other effects (fever, rash, pruritus, 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
  • Avoid using as replacement for cholera therapy
Vibrio cholerae O1 Inaba and Ogawa classic and El Tor strains, recombinant cholera toxin B
(Cholera toxin B subunit + Vaccine, cholera)		 Cholera:
2-6 years old: 3 doses PO administered at 1-week interval, booster dose within 6 months
>6 years old: 2 doses PO administered at 1-week interval, booster dose within 2 years
ETEC: 2 doses PO administered at 1- to 6-week interval

Disclaimer

All dosage recommendations are for children 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.