Ranitidine Syrup Dosing for Children
For oral ranitidine syrup in children aged 1 month to 16 years, the recommended dose is 5-10 mg/kg/day divided into 2-3 doses, with a maximum daily dose of 300 mg for treatment of GERD or peptic ulcer disease. 1
Standard Dosing Regimen
The American Academy of Pediatrics establishes the foundational dosing framework for pediatric ranitidine therapy 1:
- Dose range: 5-10 mg/kg/day 1
- Frequency: Divided into 2-3 doses per day 1
- Maximum daily dose: 300 mg 1
- Age range: 1 month to 16 years 1, 2
Age-Specific Dosing Considerations
Preterm and Term Neonates (Critical Care Setting)
Preterm infants require significantly lower doses than term neonates due to prolonged drug effect and reduced renal clearance 3:
- Preterm infants: 0.5 mg/kg twice daily (every 12 hours) 3
- Term neonates: 1.5 mg/kg three times daily (every 8 hours) 3
The time to reach maximum gastric pH is significantly longer in preterm versus term infants, and the duration of effect from a single dose is prolonged in preterm neonates 3. Plasma clearance in neonates under 1 month is considerably lower (3 mL/min/kg) compared to older children and adults, necessitating dose reduction 2.
Children 1-16 Years
For the general pediatric population, oral doses of 6-10 mg/kg/day divided into 2-3 doses maintain gastric pH >4 throughout most of the dosing interval 2. The bioavailability of oral ranitidine in pediatric patients is approximately 48%, comparable to adults 2.
Pharmacokinetic Profile in Children
Peak serum concentrations occur 2-3 hours after oral administration, with an elimination half-life of 2.5-3 hours in children with normal renal function 2:
- Cmax range: 54-492 ng/mL (depending on dose of 1-2 mg/kg) 2
- Tmax: Approximately 2.0 hours 2
- Bioavailability: 48% 2
A single 75 mg dose in children aged 4-11 years produces a median Cmax of 477 ng/mL at 2.5 hours, with intragastric pH rising within 30 minutes and remaining elevated for 5-6 hours 4.
Critical Care Dosing
For critically ill children requiring stress ulcer prophylaxis, higher and more frequent dosing is necessary 5:
- Intravenous route: 1.5 mg/kg every 6 hours achieves gastric pH ≥4 in 80% of patients 5
- Oral/NG tube route: 4 mg/kg every 12 hours 5
The higher dosing in critical care reflects increased gastric acid production and the need for consistent acid suppression 5.
Important Clinical Caveats
Non-Responders
Approximately 33% of children receiving oral ranitidine 2 mg/kg as a single dose demonstrate no measurable effect on gastric pH and volume, despite adequate serum levels 6. This suggests individual variability in receptor sensitivity or gastric acid production that may require dose adjustment or alternative therapy 6.
Tachyphylaxis
Ranitidine develops tolerance within 6 weeks of continuous use and provides only 6 hours of acid suppression, necessitating 2-3 times daily dosing 1. This is a critical limitation compared to proton pump inhibitors for long-term management 1.
Renal Impairment
Dosage reduction is necessary in children with significant renal dysfunction, as approximately 30% of the oral dose is excreted unchanged in urine 2. The elimination half-life increases proportionally with declining creatinine clearance 2.