Maximum Dose of Amoxicillin

Adult Dosing Limits

• The American Academy of Otolaryngology-Head and Neck Surgery recommends a standard maximum daily dose of oral amoxicillin for adults of 4 grams per day, regardless of patient size or weight 1
• When combined with clavulanic acid, the maximum dose remains 4 grams of amoxicillin component with 250 mg of clavulanate per day 1
• For respiratory infections requiring higher coverage against resistant organisms, high-dose amoxicillin is defined as 4 g/day 1

Pediatric Dosing Limits

• For children, high-dose amoxicillin is defined as 90 mg/kg/day, not to exceed 4000 mg/day 1
• For Group A streptococcal pharyngitis, the maximum dose is 50 mg/kg once daily (maximum 1,000 mg) or 25 mg/kg twice daily (maximum 500 mg per dose) 1

Clinical Considerations

• The upper limit of amoxicillin is often determined by gastrointestinal tolerability rather than toxicity concerns 1
• For severe infections requiring high-dose therapy, the maximum remains 4 g/day for adults, regardless of body weight 1
• In infective endocarditis treatment, ampicillin (closely related to amoxicillin) has a maximum daily dose of 12 g, but this is for intravenous administration only 2

Common Pitfalls

• Assuming that larger patients can receive doses exceeding 4 g/day is incorrect, as the maximum remains 4 g/day regardless of patient size 1
• Confusing oral amoxicillin maximum doses with intravenous ampicillin/amoxicillin doses, which can be higher in certain severe infections 2, 3

Amoxicillin Dosing Guidelines

Pediatric Dosing

• For Group A streptococcal pharyngitis, the American Academy of Family Physicians recommends a maximum dose of 50 mg/kg once daily (capped at 1000 mg) or 25 mg/kg twice daily (capped at 500 mg per dose) 4, 5
• For Haemophilus influenzae pneumonia in children, the Infectious Diseases Society of America recommends dosing ranges from 75-100 mg/kg/day, with a maximum daily dose not exceeding 4 grams 6

Intravenous vs Oral Dosing

• The Clinical Infectious Diseases journal notes that intravenous ampicillin dosing can reach 12 grams daily for severe infections, but this does not apply to oral amoxicillin 6
• For severe pneumonia in children requiring high-dose therapy, the Clinical Infectious Diseases journal recommends intravenous ampicillin can be dosed at 300-400 mg/kg/day, with oral amoxicillin having a distinct maximum dose 6, 7