What is the dosage for amoxicillin (amoxicillin) in treating bacterial infections?

Amoxicillin Dosing for Bacterial Infections

For most adult bacterial infections, amoxicillin should be dosed at 500 mg every 8 hours or 875 mg every 12 hours, with the higher dose reserved for severe infections or lower respiratory tract involvement. 1

Standard Adult Dosing by Infection Severity

Mild to Moderate Infections (Ear/Nose/Throat, Skin, Genitourinary):

• 500 mg every 12 hours OR 250 mg every 8 hours 1
• Take at the start of meals to minimize gastrointestinal intolerance 1

Severe Infections or Lower Respiratory Tract Infections:

• 875 mg every 12 hours OR 500 mg every 8 hours 1
• This higher dosing applies to all lower respiratory tract infections regardless of severity 1

Pediatric Dosing (Children ≥3 Months and <40 kg)

Mild to Moderate Infections:

• 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 1

Severe Infections or Lower Respiratory Tract Infections:

• 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 1

Infants <3 Months:

• Maximum 30 mg/kg/day divided every 12 hours due to immature renal function 1
• Do NOT exceed this dose in neonates 1

Special Infection Types

Cutaneous Infections (Cat Scratch Disease):

• 500 mg three times daily for 7-10 days 2

H. pylori Eradication (Adults Only):

• Triple therapy: 1 gram twice daily (every 12 hours) with clarithromycin 500 mg and lansoprazole 30 mg for 14 days 1
• Dual therapy: 1 gram three times daily (every 8 hours) with lansoprazole 30 mg for 14 days 1

Critical Dosing Adjustments

Severe Renal Impairment:

• GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours 1
• GFR <10 mL/min: 500 mg or 250 mg every 24 hours 1
• Hemodialysis: 500 mg or 250 mg every 24 hours, with additional dose during and after dialysis 1
• Do NOT use 875 mg dose if GFR <30 mL/min 1

Treatment Duration

Minimum Duration:

• Continue for 48-72 hours beyond symptom resolution or bacterial eradication 1

Streptococcus pyogenes Infections:

• Minimum 10 days to prevent acute rheumatic fever 1

Dental/Jaw Infections:

• 7-10 days for standard dental infections 3
• Surgical drainage is mandatory—antibiotics alone are insufficient for dental abscesses 3

When to Use Amoxicillin-Clavulanate Instead

Switch to amoxicillin-clavulanate 875/125 mg twice daily for:

• Animal or human bites 2
• Beta-lactamase producing organisms suspected 3
• Recent antibiotic use within 4-6 weeks 2
• Failed initial amoxicillin therapy 2
• More complex dental infections 3

Common Pitfalls to Avoid

Critical Error:

• Never prescribe antibiotics for dental abscesses without ensuring surgical intervention (incision/drainage or extraction) is performed—this will result in treatment failure regardless of antibiotic choice 3

Formulation Error:

• Do NOT substitute two 250 mg tablets for one 500 mg tablet when using amoxicillin-clavulanate, as this results in excessive clavulanate and increased diarrhea 3

Dosing Error:

• Infections caused by bacteria with intermediate susceptibility should receive the higher "severe infection" dosing 1

Duration Error:

• Do not stop treatment when symptoms resolve—continue for full 48-72 hours beyond symptom resolution 1