What is the normal starting dose of omeprazole (proton pump inhibitor) for a 1-month-old infant with impaired gastric function?

Normal Starting Dose of Omeprazole for a 1-Month-Old Infant

For a 1-month-old infant with impaired gastric function requiring omeprazole, the recommended starting dose is 0.7 mg/kg/day divided into two doses, which can be escalated up to 1.4-2.8 mg/kg/day based on clinical response. 1

Weight-Based Dosing Approach

• The initial dose of 0.7 mg/kg/day should be divided into two daily doses (approximately 0.35 mg/kg twice daily) for severe or refractory GERD in infants under 2 years 1
• Approximately 50% of infants require doses higher than the initial 0.7 mg/kg/day to achieve adequate acid control, necessitating dose titration based on clinical response 1
• Doses may be escalated in increments of 0.7 mg/kg/day up to a maximum of 2.8 mg/kg/day in divided doses if initial dosing proves inadequate 1, 2

Practical Administration for a 1-Month-Old

• Omeprazole should be compounded into a 6 mg/mL suspension by mixing capsule contents with applesauce or having a retail pharmacy prepare the suspension 1
• For a typical 1-month-old infant weighing approximately 4 kg, the starting dose would be approximately 2.8 mg daily (0.7 mg/kg × 4 kg), which equals 0.47 mL of 6 mg/mL suspension divided into two doses 1
• The suspension can be administered by mixing pellets from capsules with applesauce, ensuring pellets are not chewed or crushed 3

Critical Considerations for Neonates and Young Infants

• Weight-based dosing recommendations for term infants should NOT be extrapolated to premature infants due to immature renal function and risk of drug accumulation 1
• Infants have prolonged elimination half-lives (55-90 hours versus 30 hours in adults) and altered volumes of distribution, making weight-based approaches essential rather than extrapolating adult doses 1
• Infants under 4 months demonstrate higher omeprazole levels and immature metabolism, with 17% being CYP2C19 poor metabolizers, suggesting the 0.5 mg/kg dose may be more appropriate to prevent accumulation 4

Dose Titration Algorithm

1. Start with 0.7 mg/kg/day divided into two doses 1
2. Reassess clinical response after 14 days with pH monitoring if available 2
3. If inadequate response, increase by 0.7 mg/kg/day increments up to maximum 2.8 mg/kg/day 1, 2
4. Monitor for clinical improvement including reduction in irritability, feeding difficulties, and vomiting 5

Important Caveats

• FDA-approved dosing only exists for children ≥2 years of age (10 mg daily for weight 10-20 kg, 20 mg daily for weight ≥20 kg), making use in 1-month-old infants off-label 3
• The majority of infants (50%) require dose escalation beyond the initial 0.7 mg/kg/day, so close monitoring and willingness to titrate upward is essential 1, 2
• Research demonstrates that 20 mg/1.73 m² is inadequate for maintaining gastric pH >4 in infants, with 40 mg/1.73 m² being required for effective acid suppression 6
• Long-term use beyond 2-3 months should prompt reassessment of the need for continued therapy 7