Famotidine Dosing for a 3-Year-Old Weighing 28 Pounds
For a 3-year-old child weighing 28 pounds (12.7 kg), the recommended dose of famotidine is 0.5 mg/kg twice daily, which equals approximately 6.4 mg (or 6-7 mg) twice daily, for a total daily dose of approximately 12.7 mg/day. 1
Weight-Based Dosing Calculation
- Standard pediatric dosing: The guideline-recommended dose is 1 mg/kg/day divided into 2 doses 1
- For this patient: 12.7 kg × 1 mg/kg/day = 12.7 mg/day total
- Divided dosing: 12.7 mg ÷ 2 = 6.35 mg per dose, given twice daily 1
Practical Administration Using 40 mg/5 mL Suspension
- Concentration: The suspension contains 8 mg/mL 1
- Volume per dose: 6.4 mg ÷ 8 mg/mL = 0.8 mL per dose
- Frequency: Administer 0.8 mL twice daily 1
- Maximum daily dose: Should not exceed 40 mg/day in pediatric patients 1
Evidence Supporting This Dosing
The 2013 Pediatrics guideline specifically states that famotidine dosing for children aged 1-16 years is 1 mg/kg/day divided in 2 doses, with cherry-banana-mint flavored oral suspension as the available formulation 1. This dosing recommendation is supported by pharmacokinetic studies demonstrating that 0.5 mg/kg twice daily (totaling 1 mg/kg/day) effectively heals gastroduodenal ulcers in children within 8 weeks with no side effects 2.
Pharmacodynamic Considerations
- Onset of action: Antisecretory activity begins within 1 hour of oral administration 3
- Duration of effect: Acid suppression lasts approximately 10-12 hours after oral dosing 3
- Bioavailability: Oral famotidine has approximately 50% bioavailability in children 2
Important Clinical Caveats
Tachyphylaxis warning: Prolonged use of H2-receptor antagonists like famotidine can lead to rapid tachyphylaxis (decreased effectiveness) within 6 weeks of treatment 1. If long-term acid suppression is needed beyond 6-8 weeks, consider transitioning to a proton pump inhibitor rather than increasing the famotidine dose 1.
Renal function: If this child has any degree of renal impairment, dose adjustment may be necessary as famotidine is eliminated primarily through the kidneys (approximately 70% as unchanged drug) 3. The elimination half-life is prolonged nonlinearly with decreased renal function 3.
Monitoring efficacy: The duration of gastric pH elevation varies among children, with some studies showing decreased duration of efficacy after repeated doses 4. If symptoms persist despite appropriate dosing, reassess the diagnosis rather than automatically increasing the dose 4.