What is the recommended famotidine dose for a 7‑year‑old child, including weight‑based dosing, dosing frequency, maximum daily amount, and renal function adjustments?

Famotidine Dosing for a 7-Year-Old Child

For a 7-year-old child, administer famotidine 1 mg/kg/day divided into two doses (approximately 0.5 mg/kg twice daily), with a maximum daily dose of 40 mg. 1

Weight-Based Dosing Calculation

• Standard pediatric dosing is 1 mg/kg/day divided into 2 doses for children aged 1-16 years, which is the FDA-approved age range that includes 7-year-olds. 1
• For example, a 25 kg (55 lb) child would receive approximately 12.5 mg twice daily (morning and evening, about 12 hours apart). 1
• The oral suspension formulation is recommended for easier administration in this age group. 1

Maximum Daily Dose

• Do not exceed 40 mg total per day (20 mg twice daily) regardless of weight in pediatric patients. 1
• This maximum applies even if the calculated 1 mg/kg/day dose would exceed 40 mg. 1

Dosing Frequency

• Administer twice daily (every 12 hours) rather than once daily for optimal acid suppression in children. 2, 3
• The elimination half-life in children over 1 year is approximately 3.3 hours, similar to adults, supporting twice-daily dosing. 3

Renal Function Adjustments

• No dose adjustment is needed for normal renal function, as famotidine pharmacokinetics in children over 1 year are similar to adults. 2, 4
• For children with creatinine clearance <50 mL/min/1.73m², reduce the dose or extend the dosing interval, as famotidine is 70% renally eliminated. 5
• In severe renal insufficiency (creatinine clearance <10 mL/min), consider reducing to once-daily dosing or further dose reduction based on clinical response. 5

Administration Guidelines

• May be given with or without food, though administration with food may reduce gastrointestinal side effects if they occur. 1
• The oral suspension is preferred over tablets for a 7-year-old to ensure accurate dosing and ease of administration. 1

Critical Clinical Considerations and Pitfalls

• Tachyphylaxis (reduced effectiveness) can develop within 6 weeks of continuous use, which is a significant limitation of H2-receptor antagonists. 1, 6
• If symptoms persist beyond 6 weeks or the medication becomes less effective, switch to a proton pump inhibitor rather than increasing the famotidine dose. 1
• One study demonstrated that the duration of acid suppression decreased from 14.9 hours after the first dose to 6.9 hours after the second dose in children receiving repeated intravenous famotidine. 6
• Do not use adult dosing regimens for pediatric patients; always calculate based on weight in mg/kg. 1

Bioavailability and Formulation

• Oral bioavailability of famotidine is 40-50% due to incomplete absorption, which is already accounted for in the recommended oral dosing. 5
• Avoid coadministration with potent antacids, as they reduce oral absorption by 20-30%. 5