What is the recommended dosage of amoxicillin (amoxycillin) suspension for a 3-month-old child?

Amoxicillin Dosing for a 3-Month-Old Infant

For a 3-month-old infant, the recommended dose of amoxicillin suspension is 30 mg/kg/day divided every 12 hours (15 mg/kg per dose twice daily), which is the maximum safe dose for this age group due to immature renal function. 1

Age-Specific Dosing Considerations

• Infants under 12 weeks (3 months) require special dosing restrictions because of incompletely developed renal function affecting amoxicillin elimination 1
• The FDA-approved maximum dose for infants under 3 months is 30 mg/kg/day divided every 12 hours, which is substantially lower than dosing for older children 1
• For a typical 3-month-old weighing approximately 5.5 kg, this translates to approximately 82.5 mg per dose (1.65 mL of 250 mg/5 mL suspension) given twice daily 2

Indication-Based Adjustments

For Mild to Moderate Respiratory Infections

• The standard dose of 30 mg/kg/day divided every 12 hours is appropriate for most uncomplicated infections in this age group 1
• This provides adequate coverage for common pathogens including Streptococcus pneumoniae and Haemophilus influenzae (β-lactamase negative strains) 1

For Severe Infections or High-Resistance Areas

• Even in severe infections, do not exceed 30 mg/kg/day in infants under 3 months due to renal immaturity 1
• If inadequate response occurs or resistant organisms are suspected, hospitalization with intravenous antibiotics should be considered rather than increasing oral dosing 3

Critical Safety Parameters

• Treatment duration should be at least 48-72 hours beyond symptom resolution, with a minimum of 10 days for Streptococcus pyogenes infections to prevent acute rheumatic fever 1
• Clinical improvement should be evident within 48-72 hours; if no improvement occurs, reevaluation is necessary to consider resistant organisms, alternative diagnoses, or need for hospitalization 2, 3
• Hospitalization indicators include oxygen saturation <92%, respiratory rate >70 breaths/min, difficulty breathing, apnea, grunting, or inadequate feeding 3

Common Pitfalls to Avoid

• Do not use the higher dosing recommendations (45-90 mg/kg/day) intended for children over 3 months in this age group, as this significantly increases the risk of drug accumulation and toxicity 1
• Do not use the 875 mg tablet formulation or attempt to extrapolate adult dosing to infants 1
• Ensure proper reconstitution of suspension: shake well before each use and discard after 14 days (refrigeration preferred but not required) 1

Administration Guidance

• Administer at the start of a meal to minimize gastrointestinal intolerance 1
• The suspension can be placed directly on the tongue or mixed with formula, milk, or juice, but must be taken immediately after mixing 1
• Monitor for adverse effects including diarrhea, rash, and hypersensitivity reactions 2

When to Escalate Care

• If the infant shows no improvement after 48-72 hours of appropriate therapy, consider hospitalization for intravenous antibiotics 3
• For suspected Staphylococcus aureus or atypical pathogens, alternative or combination therapy may be needed, typically requiring specialist consultation 3