IV Ranitidine Dosing Per Kilogram
For pediatric patients, administer IV ranitidine at 1-1.5 mg/kg every 6-8 hours, with the higher dose of 1.5 mg/kg every 6 hours preferred for critically ill children requiring reliable gastric acid suppression. 1, 2
Standard Pediatric Dosing
The FDA-approved dosing for IV ranitidine in children is 2-4 mg/kg/day divided every 6-8 hours, with a maximum single dose of 50 mg. 1 This translates to approximately 0.5-1 mg/kg per dose when given every 6-8 hours.
However, clinical evidence demonstrates this standard dosing may be insufficient:
- For critically ill pediatric patients requiring stress ulcer prophylaxis, 1.5 mg/kg IV every 6 hours is superior to lower doses for maintaining gastric pH ≥4. 2
- In a study of 40 critically ill children, 80% of patients receiving 1.5 mg/kg every 6 hours achieved adequate acid suppression (pH ≥4 for >80% of monitoring period), compared to lower success rates with 0.75 mg/kg every 6 hours. 2
- Recent data from 628 critically ill pediatric patients showed that dosing more frequently than every 8 hours is necessary to maintain therapeutic gastric pH. 3
Neonatal Dosing
For neonates (especially those on ECMO), a single dose of 2 mg/kg IV is sufficient to increase gastric pH >4 for at least 15 hours. 1, 4
- Administer 2 mg/kg every 12-24 hours, or as a continuous infusion of 2 mg/kg/24 hours. 1, 4
- The elimination half-life in neonates is approximately 6.6 hours, supporting less frequent dosing than in older children. 4
- Continuous infusion maintains more stable gastric pH than intermittent bolus dosing in this population. 4
Special Clinical Contexts
Anaphylaxis (Adjunctive Therapy)
- Children: 1 mg/kg IV (12.5-50 mg maximum) over 5 minutes as second-line therapy after epinephrine. 5, 6, 7
- Adults: 50 mg IV diluted in 5% dextrose over 5 minutes. 5, 7
- Never administer H2 antagonists alone for anaphylaxis; they are adjunctive to epinephrine. 6, 7
Continuous Infusion
- For Zollinger-Ellison or severe hypersecretory states: Start at 1 mg/kg/hour, titrating upward in 0.5 mg/kg/hour increments based on gastric acid output. 1
- Doses up to 2.5 mg/kg/hour have been used safely. 1
- For standard acid suppression in neonates: 2 mg/kg/24 hours as continuous infusion. 1, 4
Renal Impairment Adjustments
For creatinine clearance <50 mL/min, reduce dosing to 50 mg every 18-24 hours (or proportionally reduce per-kilogram doses). 1, 8
- Ranitidine elimination half-life increases approximately 3-fold in renal failure (from ~2-3 hours to 7 hours). 8
- Renal clearance correlates significantly with creatinine clearance. 8
- Time hemodialysis doses to coincide with the end of dialysis sessions. 1
Administration Guidelines
Intermittent IV bolus: Dilute to ≤2.5 mg/mL and inject over 5 minutes (no faster than 4 mL/min). 1
Intermittent IV infusion: Dilute to ≤0.5 mg/mL and infuse over 15-20 minutes. 1
Continuous infusion: Dilute to ≤2.5 mg/mL for standard dosing. 1
Critical Pitfalls
- Avoid standard every-8-hour dosing in critically ill children—more frequent dosing (every 6 hours) or continuous infusion provides superior acid suppression. 3, 2
- Monitor gastric pH directly in high-risk patients, as clinical response varies significantly with age and renal function. 3
- Younger patients and those with impaired renal function require dose adjustments—age and kidney function significantly affect achievement of therapeutic pH. 3
- The FDA maximum of 50 mg per dose applies even to larger children and adolescents. 6, 1