Amoxicillin Dosage and Usage for Bacterial Infections
The typical adult dosage of amoxicillin for bacterial infections is 250-500 mg every 8 hours or 500-875 mg every 12 hours, with higher doses of up to 4 g/day recommended for severe infections or those caused by less susceptible organisms like penicillin-resistant Streptococcus pneumoniae. 1, 2
Adult Dosing Guidelines
- For mild to moderate ear/nose/throat, skin/skin structure, and genitourinary tract infections: 500 mg every 12 hours or 250 mg every 8 hours 2
- For severe ear/nose/throat, skin/skin structure, and genitourinary tract infections: 875 mg every 12 hours or 500 mg every 8 hours 2
- For lower respiratory tract infections (both mild/moderate and severe): 875 mg every 12 hours or 500 mg every 8 hours 2
- For high-dose therapy targeting penicillin-resistant S. pneumoniae: 4 g/day divided in 2 doses 1
- For Helicobacter pylori infection (triple therapy): 1 gram twice daily for 14 days, in combination with clarithromycin and lansoprazole 2
- For Helicobacter pylori infection (dual therapy): 1 gram three times daily for 14 days, in combination with lansoprazole 2
Pediatric Dosing Guidelines
- For children ≥3 months and <40 kg with mild/moderate infections: 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours 2
- For children ≥3 months and <40 kg with severe infections: 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours 2
- For children <12 weeks: maximum dose of 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 2
- For pediatric pneumonia in children <3 years: 80-100 mg/kg/day in three daily doses 1
- For pediatric acute otitis media: high-dose of 80-90 mg/kg/day in 2 divided doses 3
Duration of Treatment
- Treatment should generally continue for 48-72 hours beyond symptom resolution 2
- For Streptococcus pyogenes infections: minimum 10-day treatment to prevent acute rheumatic fever 2
- For sinusitis: 5-7 days in adults, 10-14 days in children 3
- For pneumococcal pneumonia: 10 days 1
- For H. pylori eradication: 14 days 2
Special Populations
- For patients with severe renal impairment (GFR 10-30 mL/min): 500 mg or 250 mg every 12 hours 2
- For patients with very severe renal impairment (GFR <10 mL/min): 500 mg or 250 mg every 24 hours 2
- For hemodialysis patients: 500 mg or 250 mg every 24 hours plus an additional dose during and at the end of dialysis 2
Administration Guidelines
- Take amoxicillin at the start of a meal to minimize gastrointestinal intolerance 2
- For oral suspension, shake well before using and refrigerate (though not required) 2
- Any unused portion of reconstituted suspension must be discarded after 14 days 2
Clinical Considerations
- Amoxicillin is generally considered the most active oral β-lactam against streptococci, including pneumococci, due to its excellent bioavailability 1
- Resistance to penicillin in S. pneumoniae is relative and can often be overcome by using higher doses of amoxicillin 1
- Amoxicillin has limited activity against β-lactamase-producing organisms; consider amoxicillin-clavulanate for these infections 1, 4
- In areas with high prevalence of penicillin-resistant S. pneumoniae, higher doses of amoxicillin are recommended 3
- Consider amoxicillin-clavulanate for patients who have received antibiotics in the previous 4-6 weeks 3
Common Pitfalls and Caveats
- Amoxicillin should only be used to treat infections proven or strongly suspected to be caused by susceptible bacteria 2
- For urinary tract infections caused by VRE, high-dose ampicillin (18-30 g IV daily) or amoxicillin 500 mg PO/IV every 8 hours may be considered 1
- For single-dose therapy of uncomplicated UTIs in adults, 3 g has shown efficacy 5
- Amoxicillin can significantly alter normal periurethral flora during treatment of urinary tract infections 6
- Amoxicillin has moderate activity against penicillin-resistant S. pneumoniae; high-dose formulations provide better coverage for these strains 7