Recommended Dosing for Amoxicillin in Enterococcus faecalis Infections
For treating Enterococcus faecalis infections, amoxicillin should be administered at a dose of 500/125 mg orally three times daily for 7 days in uncomplicated infections, with higher doses and longer durations required for severe or invasive infections. 1
Dosing Considerations Based on Infection Type
Uncomplicated Infections
- Amoxicillin 500 mg orally three times daily for 7 days
- Amoxicillin-clavulanate 500/125 mg orally three times daily for 7 days (preferred if beta-lactamase production is suspected)
Invasive Infections (including endocarditis)
- For native valve endocarditis with symptoms <3 months: 4 weeks of therapy
- For native valve endocarditis with symptoms ≥3 months: 6 weeks of therapy
- For prosthetic valve endocarditis: 6 weeks of therapy 2
Combination Therapy for Severe Infections
- Ampicillin or amoxicillin plus gentamicin is traditionally recommended for enterococcal endocarditis
- Gentamicin should be administered in multiple divided doses (total ≈3 mg·kg⁻¹·d⁻¹) rather than once daily 2
- Gentamicin dosing should be adjusted to achieve a 1-hour serum concentration of ≈3 μg/mL and a trough concentration of <1 μg/mL 2
Special Considerations
Alternative Regimens
- For patients with renal impairment who cannot tolerate aminoglycosides:
Duration of Therapy
- A 4-week course of antibiotic treatment may not be suitable for uncomplicated native valve E. faecalis endocarditis, as relapses were more frequent with 4-week versus 6-week treatment (17% vs. 2%) 4
- Patients with prosthetic valve infections should receive at least 6 weeks of therapy 2
Synergistic Combinations
- Amoxicillin has demonstrated higher bactericidal potential than ampicillin or penicillin both alone and in combination with aminoglycosides 5
- For high-level aminoglycoside-resistant strains, a combination of ampicillin and ceftriaxone is recommended 1
Common Pitfalls and Caveats
- Cephalosporins have minimal or no activity against enterococci and should not be used as monotherapy 1
- High rates of fluoroquinolone resistance have been observed in E. faecalis strains, making these agents less reliable for empiric therapy 1
- Nitrofurantoin should be avoided in patients with significant renal impairment (creatinine clearance <30 mL/min) 1
- Prolonged aminoglycoside therapy increases the risk of nephrotoxicity and ototoxicity, requiring careful monitoring of drug levels and renal function 2
By following these evidence-based dosing recommendations and considering the specific type and severity of E. faecalis infection, clinicians can optimize treatment outcomes while minimizing adverse effects.