Amoxicillin Dosage and Usage for Bacterial Infections
For treating bacterial infections, amoxicillin dosing should be tailored to the specific infection type, with adults typically receiving 500-875 mg every 12 hours or 250-500 mg every 8 hours, and children receiving 25-45 mg/kg/day divided into twice or three-times daily dosing, continuing treatment for at least 48-72 hours after symptom resolution. 1
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 1
- For severe ear/nose/throat, skin/skin structure, and genitourinary tract infections: 875 mg every 12 hours or 500 mg every 8 hours 1
- For lower respiratory tract infections (mild/moderate or severe): 875 mg every 12 hours or 500 mg every 8 hours 1
- For H. pylori infection with duodenal ulcer disease:
- For uncomplicated urinary tract infections with vancomycin-resistant enterococci: amoxicillin 500 mg orally/IV every 8 hours 2
- For dental/tooth infections: 500 mg orally three times daily for 7-10 days 3
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 1
- 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 1
- For children <12 weeks (3 months): maximum 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 1
- For Group A Streptococcus infections: amoxicillin 50-75 mg/kg/day in 2 doses 4
- For Haemophilus influenzae (β-lactamase negative): amoxicillin 75-100 mg/kg/day in 3 doses 4
Treatment Duration
- Continue treatment for a minimum of 48-72 hours after the patient becomes asymptomatic or bacterial eradication is evident 1
- For Streptococcus pyogenes infections: minimum 10 days treatment to prevent acute rheumatic fever 1
- For H. pylori infection: 14 days of treatment 1
- For dental infections: 7-10 days 3
Special Considerations
Renal Impairment Dosing
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours, depending on infection severity 1
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours, depending on infection severity 1
- Hemodialysis: 500 mg or 250 mg every 24 hours with additional dose during and at end of dialysis 1
- Patients with GFR <30 mL/min should NOT receive the 875 mg dose 1
Administration Guidelines
- Take amoxicillin at the start of a meal to minimize gastrointestinal intolerance 1
- For oral suspension: shake well before using; refrigeration is preferable but not required 1
- Discard any unused reconstituted suspension after 14 days 1
Common Pitfalls and Caveats
- Amoxicillin alone may be ineffective against β-lactamase-producing organisms; consider amoxicillin-clavulanate for suspected β-lactamase producers 5
- For penicillin-resistant S. pneumoniae with MICs ≥4.0 μg/mL, alternative therapies like ceftriaxone should be considered 4
- Amoxicillin may reduce the efficacy of oral contraceptives 1
- Serious and occasionally fatal anaphylactic reactions have been reported; discontinue if a reaction occurs 1
- Clostridioides difficile-associated diarrhea can range from mild to fatal; evaluate if diarrhea develops 1
- Coadministration with probenecid is not recommended 1
- Concomitant use with oral anticoagulants may increase prothrombin time prolongation 1
- Coadministration with allopurinol increases risk of rash 1
For community-acquired pneumonia, amoxicillin remains effective for susceptible pathogens, but recent research suggests limited benefit for acute sinusitis when comparing high-dose versus standard-dose amoxicillin-clavulanate 6. However, amoxicillin continues to be an important agent in treating community-acquired respiratory tract infections due to its favorable pharmacokinetic profile and broad spectrum of activity 5.