Maximum Recommended Adult Dose of Amoxicillin
The maximum adult dose of amoxicillin is 3 grams per day (1 gram every 8 hours), though specific severe infections may require up to 4 grams per day in divided doses.
Standard Maximum Dosing
According to FDA labeling, the highest approved adult dosing regimen for amoxicillin is 875 mg every 12 hours or 500 mg every 8 hours for severe infections 1. This translates to:
- Maximum daily dose: 1,750 mg (using 875 mg twice daily)
- Alternative maximum: 1,500 mg daily (using 500 mg three times daily)
However, for specific severe infections, higher doses are used:
Context-Specific Maximum Doses
For Severe Respiratory and Systemic Infections
- Up to 3 grams daily (1 gram every 8 hours) is commonly used for severe community-acquired pneumonia and other serious infections 2, 3
- This dosing is supported by clinical practice for treating penicillin-intermediate Streptococcus pneumoniae 3
For H. pylori Eradication
- 1 gram three times daily (total 3 grams/day) when used in triple therapy with clarithromycin and lansoprazole 1
For Endocarditis
- Up to 12 grams daily in divided doses every 4-6 hours for ampicillin (amoxicillin's IV equivalent) in severe endocarditis 4
Important Clinical Considerations
Renal function is the critical limiting factor. Patients with normal renal function can tolerate higher doses, but those with GFR <30 mL/min should NOT receive the 875 mg dose and require dose reduction 1:
- GFR 10-30 mL/min: Maximum 500 mg every 12 hours
- GFR <10 mL/min: Maximum 500 mg every 24 hours
- Hemodialysis: 500 mg every 24 hours plus additional dose during and after dialysis
The 875 mg tablet formulation produces peak levels of 13.8 mcg/mL, which is adequate for most susceptible organisms 1.
Common Pitfall to Avoid
Do not routinely exceed 3 grams daily in outpatient settings without specific indication. While doses up to 4 grams daily appear in some guidelines for severe infections 5, the standard maximum for most adult infections remains 1.5-3 grams daily depending on severity 1, 3. Higher doses increase risk of crystalluria and renal complications, particularly in patients with any degree of renal impairment 1.