›Adults
›Ondansetron 4 to 8 mg PO, IV, or ODT for vomiting
›Facilitates oral rehydration by reducing vomiting episodes
›May increase stool volume: monitor fluid balance
›Children > 4 years
›Ondansetron ODT 0.15 mg/kg per dose (max 4 mg) x 1 dose
›Single dose effective to facilitate oral rehydration
›Evidence supports use in children: reduces vomiting and IV fluid need
›Precautions
›QT prolongation risk with high doses or cardiac comorbidity
›Avoid in patients with prolonged QT on ECG
›Loperamide (adults only)
›Indication
›Acute watery non-bloody non-febrile diarrhea in adults
›Reduces stool frequency and duration of illness
›Dosing
›4 mg PO initial dose
›Then 2 mg PO after each unformed stool
›Maximum 8 mg per day for up to 48 hours
›Contraindications
›Bloody or inflammatory diarrhea: risk of toxic megacolon
›Febrile dysentery
›Children < 18 years per IDSA guidelines
›Children < 2 years: respiratory depression risk
›Bismuth subsalicylate
›Indication
›Mild antisecretory effect in viral or traveler diarrhea
›Alternative when loperamide contraindicated
›Dosing adults
›525 mg PO every 30 to 60 minutes as needed
›Maximum 8 doses in 24 hours
›Contraindications
›Children < 12 years: Reye syndrome risk from salicylate component
›Aspirin allergy or bleeding risk
›Resume oral intake within 4 to 6 hours of rehydration
›Age-appropriate regular diet recommended
›No evidence BRAT diet (banana, rice, applesauce, toast) superior to normal diet
›Normal diet shortens illness duration and improves nutritional outcomes
›Foods to avoid acutely
›High-fat and high-sugar foods
›Caffeine and alcohol
›Lactose-containing foods may transiently worsen diarrhea
›Routine lactose avoidance not universally recommended
›IV fluid indications
›Failure of oral rehydration despite antiemetics
›Severe dehydration or hemodynamic compromise
›Altered mental status precluding oral intake
›IV fluid selection
›Normal saline 0.9% or lactated Ringer isotonic solution
›Balanced crystalloids preferred to minimize hyperchloremic acidosis
›Particularly relevant in prolonged or severe illness
›Rate and volume
›Bolus 20 mL/kg for hemodynamic instability
›Maintenance rate adjusted to urine output and ongoing losses
›Electrolyte replacement guided by metabolic panel
›Potassium replacement
›Oral potassium if K+ 3.0 to 3.5 mmol/l and tolerating PO
›KCl 20 to 40 mmol PO in divided doses
›IV potassium if K+ < 3.0 mmol/l or unable to take PO
›Maximum 10 mmol/hour peripheral IV
›Cardiac monitoring during IV replacement
›Sodium correction
›Hyponatremia: correct slowly to avoid osmotic demyelination
›Maximum 8 mmol/l increase per 24 hours in chronic hyponatremia
›Faster correction acceptable in acute symptomatic hyponatremia
›Hypernatremia: correct slowly to avoid cerebral edema
›Maximum 10 mmol/l decrease per 24 hours