What antibiotics are used to treat endocarditis?

Antibiotic Treatment for Infective Endocarditis

The treatment of infective endocarditis requires specific antibiotic regimens based on the causative pathogen, with first-line therapy typically including ampicillin/amoxicillin plus gentamicin for streptococcal/enterococcal endocarditis and (flu)cloxacillin or oxacillin for staphylococcal endocarditis, administered intravenously for 4-6 weeks. 1, 2

Pathogen-Specific Treatment Regimens

Staphylococcal Endocarditis

• Native valve infections (methicillin-susceptible):

  • First-line: (Flu)cloxacillin or oxacillin 12 g/day IV in 4-6 doses for 4-6 weeks 1
  • Alternative for penicillin allergy: Cefazolin 6 g/day or cefotaxime 6 g/day IV in 3 doses 1
  • For MRSA: Vancomycin 30-60 mg/kg/day IV in 2-3 doses for 4-6 weeks 1, 3
  • Alternative for MRSA: Daptomycin 10 mg/kg/day IV once daily for 4-6 weeks 1, 4

• Prosthetic valve infections:

  • (Flu)cloxacillin or oxacillin 12 g/day IV in 4-6 doses for ≥6 weeks PLUS
  • Rifampin 900-1200 mg IV/oral in 2-3 divided doses for ≥6 weeks AND
  • Gentamicin 3 mg/kg/day IV/IM in 1-2 doses for 2 weeks 1
  • For MRSA: Replace (flu)cloxacillin with vancomycin 1

Enterococcal Endocarditis

• First-line therapy:

  • Amoxicillin 200 mg/kg/day IV in 4-6 doses for 6 weeks (8 weeks for prosthetic valve) PLUS
  • Gentamicin 3 mg/kg/day IV/IM in 1 dose for 2-6 weeks 1

• Alternative regimen (especially for high-level aminoglycoside resistance):

  • Ampicillin 200 mg/kg/day IV in 4-6 doses PLUS
  • Ceftriaxone 4 g/day IV/IM in 2 doses for 6 weeks 1

• For penicillin-allergic patients:

  • Vancomycin 30 mg/kg/day IV in 2 doses PLUS
  • Gentamicin 3 mg/kg/day IV/IM in 1 dose for 6 weeks 1

Streptococcal Endocarditis (Viridans Group)

• Penicillin-susceptible strains:
  • Penicillin G or Ampicillin/Amoxicillin for 4 weeks 1, 2
  • Short-course option: Penicillin/Ampicillin plus Gentamicin for 2 weeks 5

Empiric Treatment

When the causative organism is unknown, empiric therapy should be initiated:

• Community-acquired native valve or late prosthetic valve infections:

  • Ampicillin-sulbactam 200-300 mg/kg/day IV divided every 4-6 hours (up to 12g daily) PLUS
  • Gentamicin 3-6 mg/kg/day IV divided every 8 hours
  • Consider adding vancomycin if MRSA is suspected 2

• Nosocomial or early prosthetic valve endocarditis:

  • Vancomycin 60 mg/kg/day IV divided every 6 hours (up to 2g daily) PLUS
  • Gentamicin 3-6 mg/kg/day IV divided every 8 hours PLUS
  • Cefepime or ceftazidime
  • Add rifampin if prosthetic material is present 2

Treatment Duration

• Minimum 4 weeks for native valve endocarditis
• Extended to 6 weeks for prosthetic valve endocarditis 2
• 6 weeks for non-HACEK Gram-negative bacilli
• 4 weeks for HACEK organisms in native valve endocarditis 2

Important Considerations

Monitoring During Treatment

• Daily clinical assessment
• Serial blood cultures to confirm clearance of bacteremia
• Echocardiographic follow-up during and after treatment
• Monitor renal function and drug levels (especially for aminoglycosides and vancomycin) 2

Common Pitfalls to Avoid

1. Inadequate empiric coverage: Ensure broad coverage until culture results are available
2. Failure to consult specialists: Early consultation with infectious disease specialists is strongly recommended
3. Premature narrowing of antibiotic spectrum: Wait for definitive culture results
4. Inadequate duration of therapy: Complete the full recommended course
5. Delayed surgical evaluation: Consider early surgical intervention for specific indications 2

Surgical Indications

Consider surgical intervention for:

• Heart failure due to valve dysfunction
• Uncontrolled infection (abscess, false aneurysm, fistula)
• Prevention of embolic events
• Prosthetic valve endocarditis, especially with S. aureus 2

Special Populations

• Pediatric patients: Similar antibiotic regimens with dose adjustments based on weight 1, 6
• Penicillin-allergic patients: Use vancomycin or cephalosporins (if non-anaphylactic reaction) 1

Bactericidal antibiotics should be used whenever possible, and all antibiotics should be administered intravenously rather than intramuscularly, especially in children 2.