What is the recommended dose of ranitidine (histamine H2-receptor antagonist) for children?

Ranitidine Dosing in Children

For pediatric patients requiring ranitidine, the recommended dose is 1 mg/kg per dose (range 12.5-50 mg, maximum 50 mg per dose) for intramuscular or intravenous administration in acute settings like anaphylaxis, or 2-4 mg/kg per dose orally every 12 hours for gastrointestinal indications. 1, 2

Context-Specific Dosing Recommendations

For Anaphylaxis (Acute Parenteral Administration)

• Administer 1 mg/kg per dose (12.5-50 mg range, maximum 50 mg) intramuscularly or intravenously 1, 2
• For IV administration, dilute in 5% dextrose to a total volume of 20 mL and inject over 5 minutes 1
• Critical caveat: Ranitidine is second-line therapy to epinephrine and should NEVER be administered alone in anaphylaxis 1, 2
• Combination of diphenhydramine plus ranitidine is superior to diphenhydramine alone 1, 2

For Gastrointestinal Indications (Oral Administration)

Standard dosing:

• Oral: 2-4 mg/kg per dose every 12 hours (based on indication severity) 3, 4
• Maximum single dose: 150 mg 5

Evidence-based dosing considerations:

• For mild GERD symptoms: 75 mg fixed dose (approximately 1.5-2.7 mg/kg in children 4-11 years) provides 5-6 hours of acid suppression 6
• For sustained acid suppression beyond 6 hours: Doses ≥3 mg/kg per dose are required 4
  • Low doses (<3 mg/kg) maintained gastric pH >4 for only 29% of time during hours 4-6 post-dose
  • High doses (≥3 mg/kg) maintained gastric pH >4 for 89% of time during hours 4-6 post-dose 4

For Critically Ill Children (Stress Ulcer Prophylaxis)

Intravenous administration:

• 1.5 mg/kg IV every 6 hours is most effective for maintaining gastric pH ≥4 3
  • This regimen achieved pH ≥4 for >80% of the study period in 80% of patients
  • Alternative: 4 mg/kg/day total dose (1 mg/kg every 6 hours or continuous infusion) 7

Continuous infusion option:

• 0.15 mg/kg bolus followed by 0.15 mg/kg/hour continuous infusion 7
• Both bolus and continuous infusion regimens at 4 mg/kg/day total are equally effective 7

For Neonates

Special population considerations:

• Initial dose: 2 mg/kg IV over 10 minutes 8
• Maintenance: 2 mg/kg/24 hours as continuous infusion maintains gastric pH >4 in >90% of patients 8
• Neonates have significantly prolonged elimination half-life (6.61 hours vs. 2-3 hours in older children) 8
• Dosing frequency should not exceed every 12 hours in term neonates with stable renal/hepatic function 8
• Plasma clearance in neonates <1 month is considerably lower (3 mL/min/kg) than in older children or adults 5

Important Clinical Considerations

Bioavailability and Absorption

• Oral bioavailability is approximately 48-50% in children, comparable to adults 5
• Peak levels occur 2-3 hours after oral dosing 5, 6
• Food and antacids do not significantly impair absorption 5

Renal Dosing Adjustments

• Ranitidine is primarily renally eliminated (30% unchanged in urine) 5
• In patients with creatinine clearance 25-35 mL/min, elimination half-life increases to 4.8 hours 5
• Dose reduction required in proportion to creatinine clearance reduction 5

Common Pitfalls to Avoid

1. Never use ranitidine as monotherapy for anaphylaxis - it is adjunctive only to epinephrine 1, 2
2. Avoid underdosing for sustained acid suppression - doses <3 mg/kg provide inadequate duration of effect beyond 4-6 hours 4
3. Do not use adult dosing in neonates - significantly reduced clearance requires lower doses and longer intervals 5, 8
4. Monitor gastric pH when possible - individual response varies and dose adjustment may be needed 8, 7

Route-Specific Summary

Route	Indication	Dose	Frequency
IM/IV	Anaphylaxis	1 mg/kg (max 50 mg)	As needed [1,2]
IV	Critically ill children	1.5 mg/kg	Every 6 hours [3]
IV continuous	Neonates/ECMO	2 mg/kg/24h	Continuous [8]
Oral	GERD (standard)	2-4 mg/kg	Every 12 hours [3,4]
Oral	GERD (sustained)	≥3 mg/kg (max 150 mg)	Every 12 hours [4]