What is the appropriate dose of ranitidine (histamine H2-receptor antagonist) for a 5.5 kg patient?

Ranitidine Dosing for a 5.5 kg Pediatric Patient

The appropriate dose of ranitidine for a 5.5 kg pediatric patient is 2-4 mg/kg/day divided every 6-8 hours, which equals approximately 11-22 mg total daily dose (or 3.7-7.3 mg per dose given three times daily). 1

IV/IM Administration Guidelines

• For parenteral administration in pediatric patients, the recommended total daily dose is 2-4 mg/kg, divided and administered every 6-8 hours, up to a maximum of 50 mg per dose 1
• For a 5.5 kg patient, this translates to:
  • Minimum dose: 2 mg/kg/day = 11 mg total daily dose
  • Maximum dose: 4 mg/kg/day = 22 mg total daily dose
  • Individual doses would be 3.7-7.3 mg given every 6-8 hours 1
• For intramuscular injection specifically, the standard pediatric dose is 1 mg/kg per dose (5.5 mg for this patient) 2

Continuous Infusion Option

• If continuous IV infusion is required, ranitidine can be added to 5% dextrose or other compatible IV solution 1
• For neonates and very small infants on ECMO, a dose of 2 mg/kg given every 12-24 hours or as a continuous infusion has been shown to increase gastric pH to >4 for at least 15 hours 1

Administration Considerations

• When administering ranitidine as an intermittent IV infusion, dilute to a concentration no greater than 0.5 mg/mL and infuse at a rate no greater than 5-7 mL/min (over 15-20 minutes) 1
• For intermittent bolus, dilute to a concentration no greater than 2.5 mg/mL and inject at a rate no greater than 4 mL/min (over 5 minutes) 1
• No dilution is necessary for intramuscular injection 1

Clinical Considerations

• Ranitidine is 4-10 times more potent than cimetidine in inhibiting gastric acid secretion 3
• When used in anaphylaxis management, ranitidine should be considered a second-line therapy to epinephrine and should never be administered alone 2
• In patients with impaired renal function, dosage adjustment may be necessary, though specific pediatric guidelines for renal impairment are not well established 1

Monitoring and Safety

• Ranitidine has an excellent safety profile with adverse events reported at rates similar to placebo in clinical trials 4
• Unlike cimetidine, ranitidine does not have antiandrogenic effects and does not alter hepatic metabolism of drugs 3, 5
• Monitor for common side effects, which are generally minimal but may include headache, dizziness, or gastrointestinal disturbances 6

Practical Dosing Recommendation

• For this 5.5 kg patient, a practical dosing regimen would be 5.5 mg (1 mg/kg) every 8 hours via IV or IM route 2, 1
• If using for anaphylaxis management, combine with diphenhydramine for superior efficacy compared to diphenhydramine alone 2