Famotidine Dosing for a 31-kg Child: 2 mL per Dose is Safe and Appropriate
Yes, you can give 2 mL per dose of famotidine 40 mg/5 mL suspension to a 31-kg child, as this delivers 16 mg per dose, which falls within the recommended weight-based dosing range. 1
Dose Calculation and Rationale
- The concentration is 40 mg per 5 mL, which equals 8 mg/mL 2
- 2 mL delivers 16 mg of famotidine per dose
- For a 31-kg child, the recommended dose is 1 mg/kg/day divided into 2 doses 1
- This calculates to 31 mg total daily, or 15.5 mg per dose (twice daily) 1
- Your proposed 16 mg per dose (2 mL) is appropriate and matches guideline recommendations 1
Dosing Schedule
- Administer 2 mL (16 mg) twice daily, approximately every 12 hours 1, 3
- The twice-daily schedule is supported by pharmacodynamic data showing that gastric pH increases within 30 minutes, peaks at 2.5 hours, and acid-inhibiting effects last approximately 6 hours 1, 3
- For children over 3 months of age, pharmacokinetic parameters are similar to adults, supporting the 12-hour dosing interval 3, 4
Age and Weight Appropriateness
- Famotidine is FDA-approved for children aged 1 to 16 years 1
- The pediatric dosing guideline specifies 1 mg/kg/day divided into 2 doses for children in this age range 1
- Studies demonstrate that children over 1 year of age handle famotidine similarly to adults, with comparable pharmacokinetics 4, 5, 6
Important Clinical Considerations
- Famotidine can be administered with or without food, though tolerability may be enhanced with meals 2
- A critical caveat: H2-receptor antagonists like famotidine develop tachyphylaxis (reduced effectiveness) within 6 weeks of continuous use 1, 3
- This tachyphylaxis limits long-term efficacy and may necessitate switching to proton pump inhibitors if prolonged acid suppression is needed 1
- Monitor for decreased duration of efficacy with prolonged use, as studies show the duration of pH elevation decreases with repeated dosing 7
Safety Profile
- Famotidine has been studied in over 150 pediatric patients and demonstrates a favorable safety profile 5
- No significant side effects were observed in pediatric studies, with only transient mild liver enzyme elevations noted in some cases, not attributable to the drug 8
- Unlike cimetidine, famotidine does not interact with cytochrome P450 enzymes and is not associated with gynecomastia or increased liver disease risk 1, 5