Famotidine Dosing Schedule for Infants
For infants with gastroesophageal reflux disease, famotidine should be administered at 0.5 mg/kg divided into two doses given every 12 hours for infants older than 3 months, or once daily for infants younger than 3 months. 1, 2
Age-Based Dosing Frequency
The timing of famotidine administration in infants is fundamentally determined by age due to developmental differences in renal function:
Infants Under 3 Months
- Administer 0.5 mg/kg once daily 2
- Reduced dosing frequency is necessary because plasma and renal clearance of famotidine are significantly decreased in this age group compared to older infants 2
- The immature renal function in young infants results in prolonged drug elimination, making once-daily dosing appropriate 2
Infants Over 3 Months to 1 Year
- Administer 0.5 mg/kg divided into two doses every 12 hours 1, 2
- Pharmacokinetic parameters in infants older than 3 months are similar to those in children and adults, supporting twice-daily dosing 2
- The 12-hour interval aligns with the approximately 6-hour duration of acid-inhibiting effects, providing more consistent gastric acid suppression 1
Clinical Context and Rationale
The twice-daily dosing schedule (every 12 hours) for older infants is supported by pharmacodynamic data showing that gastric pH begins to increase within 30 minutes of H2-receptor antagonist administration and reaches peak plasma concentrations at 2.5 hours, with acid-inhibiting effects lasting approximately 6 hours. 1
Practical Administration Timing
- For infants over 3 months: typical schedules include morning (e.g., 8 AM) and evening (e.g., 8 PM) doses to maintain consistent acid suppression throughout the day and night 1
- For infants under 3 months: a single daily dose can be given at the same time each day, typically in the morning 2
Important Dosing Considerations
Dose Adjustment Based on Response
- While 0.5 mg/kg is the standard starting dose, some infants may require individualization based on clinical response 3
- A study demonstrated that 1.0 mg/kg may be more efficacious in some infants for reducing crying time and regurgitation frequency, though 0.5 mg/kg showed significant improvements in regurgitation frequency 3
Safety Profile
- Short-course famotidine therapy appears generally well tolerated in infants 2
- Possible adverse effects include agitation, irritability (sometimes manifested as head-rubbing), somnolence, and headache 3
- No accumulation occurs with multiple dosing when age-appropriate frequencies are used 2
Common Pitfalls to Avoid
- Do not use twice-daily dosing in infants under 3 months of age - this can lead to drug accumulation due to immature renal clearance 2
- Do not assume adult dosing schedules apply to young infants - the pharmacokinetics differ significantly in the first 3 months of life 2
- Be aware that H2-receptor antagonists can develop tachyphylaxis within 6 weeks, potentially limiting long-term efficacy 1