What are the recommended antimicrobial dosing regimens for common infections in a hospital and clinic setting?

Hospital and Clinic Antimicrobial Dosing Reference Guide

Intra-Abdominal Infections

For complicated intra-abdominal infections in adults, use piperacillin-tazobactam 3.375 g IV every 6 hours, or a carbapenem such as meropenem 1 g IV every 8 hours or ertapenem 1 g IV every 24 hours, combined with source control measures. 1

Adult Dosing Options

Beta-lactam/Beta-lactamase Inhibitor Combinations:

• Piperacillin-tazobactam: 3.375 g IV every 6 hours (increase to 3.375 g every 4 hours or 4.5 g every 6 hours for Pseudomonas aeruginosa) 1
• Ticarcillin-clavulanic acid: 3.1 g IV every 6 hours 1

Carbapenems:

• Meropenem: 1 g IV every 8 hours 1
• Imipenem/cilastatin: 500 mg IV every 6 hours or 1 g every 8 hours 1
• Ertapenem: 1 g IV every 24 hours 1
• Doripenem: 500 mg IV every 8 hours 1

Cephalosporins (require anaerobic coverage with metronidazole):

• Cefepime: 2 g IV every 8-12 hours 1, 2
• Cefotaxime: 1-2 g IV every 6-8 hours 1
• Ceftriaxone: 1-2 g IV every 12-24 hours 1
• Ceftazidime: 2 g IV every 8 hours 1

Fluoroquinolones (require anaerobic coverage with metronidazole):

• Ciprofloxacin: 400 mg IV every 12 hours 1
• Levofloxacin: 750 mg IV every 24 hours 1
• Moxifloxacin: 400 mg IV every 24 hours 1

Anaerobic Coverage:

• Metronidazole: 500 mg IV every 8-12 hours or 1500 mg every 24 hours 1

Aminoglycosides (for severe infections, dose based on adjusted body weight):

• Gentamicin or tobramycin: 5-7 mg/kg IV every 24 hours with serum monitoring 1
• Amikacin: 15-20 mg/kg IV every 24 hours with serum monitoring 1

Vancomycin (for MRSA or resistant enterococci, dose based on total body weight):

• 15-20 mg/kg IV every 8-12 hours with serum monitoring 1

Duration of Therapy

Limit antimicrobial therapy to 4-7 days for established intra-abdominal infections with adequate source control; longer durations have not improved outcomes. 1

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Community-Acquired Pneumonia

Outpatient Treatment (Healthy Adults Without Comorbidities)

For previously healthy adults with community-acquired pneumonia, prescribe amoxicillin 1 g orally three times daily for 5-7 days as first-line therapy. 3

Alternative Options:

• Doxycycline: 100 mg orally twice daily 3
• Azithromycin: 500 mg orally on day 1, then 250 mg daily for 4 days (only if local pneumococcal macrolide resistance <25%) 3
• Clarithromycin: 250-500 mg orally twice daily 1

Outpatient Treatment (Adults With Comorbidities)

For adults with comorbidities (COPD, diabetes, heart failure, chronic kidney disease), use combination therapy with amoxicillin-clavulanate 1 g orally every 8 hours plus azithromycin 500 mg daily, or monotherapy with a respiratory fluoroquinolone. 3

Respiratory Fluoroquinolones:

• Levofloxacin: 750 mg orally every 24 hours 1, 3
• Moxifloxacin: 400 mg orally every 24 hours 1, 3

Inpatient Treatment (Medical Ward)

For hospitalized patients with community-acquired pneumonia, administer ceftriaxone 1 g IV every 24 hours or cefotaxime 1 g IV every 8 hours plus azithromycin 500 mg IV/orally daily, or use respiratory fluoroquinolone monotherapy. 1, 3

Alternative Beta-lactams:

• Cefuroxime: 750-1500 mg IV every 8 hours 1
• Ampicillin-sulbactam: 1.5-3.0 g IV every 6 hours 1

Severe CAP (ICU Patients)

For severe community-acquired pneumonia requiring ICU admission, use ceftriaxone 1 g IV every 24 hours or cefotaxime 1 g IV every 8 hours plus either azithromycin 500 mg IV daily or a respiratory fluoroquinolone. 3

When Pseudomonas aeruginosa is suspected:

• Cefepime 2 g IV every 8 hours or piperacillin-tazobactam 4.5 g IV every 6 hours 1, 2
• Plus ciprofloxacin 400 mg IV every 12 hours or an aminoglycoside 3
• Plus azithromycin 500 mg IV daily 3

Duration of Therapy

Treat for 5-7 days in responding patients; extend to 14-21 days only for confirmed Legionella pneumophila, Staphylococcus aureus, or gram-negative enteric bacilli. 3

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Skin and Soft Tissue Infections

Simple Abscesses

For simple abscesses or boils caused by community-acquired MRSA, perform incision and drainage without antibiotics unless systemic signs of infection are present. 1

Purulent Cellulitis (Outpatient)

For purulent cellulitis, prescribe trimethoprim-sulfamethoxazole 1-2 double-strength tablets orally twice daily for 5-10 days. 1

Alternative Options:

• Clindamycin: 300-450 mg orally three times daily 1
• Doxycycline: 100 mg orally twice daily 1
• Linezolid: 600 mg orally twice daily 1

Non-Purulent Cellulitis (Outpatient)

For non-purulent cellulitis, use cephalexin 500 mg orally four times daily to cover beta-hemolytic streptococci; add MRSA coverage if the patient fails to respond to beta-lactam therapy. 1

Complicated SSTI (Inpatient)

For hospitalized patients with complicated skin and soft tissue infections, administer vancomycin 15-20 mg/kg IV every 8-12 hours (target trough 15-20 mcg/mL) or linezolid 600 mg IV every 12 hours. 1

Alternative Options:

• Daptomycin: 4 mg/kg IV every 24 hours 1
• Telavancin: 10 mg/kg IV every 24 hours 1

Animal Bites

For animal bites, prescribe amoxicillin-clavulanate 875 mg orally twice daily for 7-10 days to cover Pasteurella multocida, staphylococci, streptococci, and anaerobes. 1

Inpatient/Severe Bites:

• Ampicillin-sulbactam: 1.5-3.0 g IV every 6-8 hours 1
• Piperacillin-tazobactam: 3.375 g IV every 6-8 hours 1

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MRSA Infections

Bacteremia (Uncomplicated)

For uncomplicated MRSA bacteremia (no endocarditis, no implanted devices, clearance within 2-4 days), use vancomycin 15-20 mg/kg IV every 8-12 hours for 2 weeks. 1

Alternative:

• Daptomycin: 6 mg/kg IV every 24 hours 1

Bacteremia (Complicated)

For complicated MRSA bacteremia (persistent fever, metastatic foci, or endocarditis), administer vancomycin 15-20 mg/kg IV every 8-12 hours or daptomycin 6-10 mg/kg IV every 24 hours for 4-6 weeks. 1

Infective Endocarditis (Native Valve)

For MRSA native valve endocarditis, use vancomycin 15-20 mg/kg IV every 8-12 hours for 6 weeks; do not add gentamicin or rifampin. 1

Infective Endocarditis (Prosthetic Valve)

For MRSA prosthetic valve endocarditis, administer vancomycin 15-20 mg/kg IV every 8-12 hours plus rifampin 300 mg orally/IV every 8 hours plus gentamicin 1 mg/kg IV every 8 hours for 6 weeks. 1

Pneumonia

For MRSA pneumonia, use vancomycin 15-20 mg/kg IV every 8-12 hours or linezolid 600 mg IV/orally every 12 hours for 7-21 days. 1

Osteomyelitis

For MRSA osteomyelitis with surgical debridement, prescribe vancomycin 15-20 mg/kg IV every 8-12 hours or daptomycin 6 mg/kg IV every 24 hours; consider adding rifampin 600 mg daily. 1

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Febrile Neutropenia

For high-risk febrile neutropenic patients, initiate empiric monotherapy with cefepime 2 g IV every 8 hours, meropenem 1 g IV every 8 hours, or piperacillin-tazobactam 4.5 g IV every 6 hours. 1

When to Add Vancomycin

Add vancomycin 15-20 mg/kg IV every 8-12 hours only for suspected catheter-related infection, skin/soft tissue infection, pneumonia, or hemodynamic instability; do not use vancomycin routinely. 1

Duration

Continue antibiotics until absolute neutrophil count exceeds 500 cells/mm³ or for the full treatment course of documented infections. 1

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Vancomycin-Resistant Enterococcus (VRE)

For VRE bloodstream infections, use linezolid 600 mg IV every 12 hours or daptomycin 6-12 mg/kg IV every 24 hours; consider adding a beta-lactam if daptomycin MIC is 3-4 mg/mL. 1

For VRE complicated urinary tract infections:

• Linezolid: 600 mg IV every 12 hours for 5-7 days 1
• Daptomycin: 6-12 mg/kg IV every 24 hours for 5-7 days 1

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Pediatric Dosing Considerations

Intra-Abdominal Infections (Neonates)

For neonatal necrotizing enterocolitis or perforated bowel, use ampicillin, gentamicin, and metronidazole; substitute vancomycin for ampicillin if MRSA or ampicillin-resistant enterococci are suspected. 1

Community-Acquired Pneumonia (Pediatric)

For children with community-acquired pneumonia, administer amoxicillin 40-90 mg/kg/day orally in 2-3 divided doses (maximum 4000 mg/day). 3

MRSA Infections (Pediatric)

For pediatric MRSA skin infections, use clindamycin 10-13 mg/kg/dose orally every 6-8 hours (maximum 40 mg/kg/day) or trimethoprim-sulfamethoxazole 4-6 mg/kg/dose (trimethoprim component) orally every 12 hours. 1

For severe pediatric MRSA infections:

• Vancomycin: 15 mg/kg IV every 6 hours 1
• Linezolid: 10 mg/kg IV/orally every 8 hours (maximum 600 mg/dose) 1, 4
• Daptomycin: 6-10 mg/kg IV every 24 hours (ages 1-17 years) 1

Febrile Neutropenia (Pediatric)

For pediatric febrile neutropenia, administer cefepime 50 mg/kg IV every 8 hours (maximum 2 g/dose) for moderate-to-severe infections or Pseudomonas coverage. 1, 2

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Renal Dose Adjustments

Cefepime

For creatinine clearance 30-60 mL/min, reduce cefepime to the same dose every 24 hours; for CrCl 11-29 mL/min, reduce dose by 50% and give every 24 hours; for CrCl <11 mL/min, reduce dose by 75% and give every 24 hours. 2

For hemodialysis patients, give cefepime 1 g on day 1, then 500 mg every 24 hours after dialysis. 2

Vancomycin

Adjust vancomycin dosing based on renal function and therapeutic drug monitoring; target trough concentrations of 15-20 mcg/mL for serious infections (bacteremia, endocarditis, pneumonia, meningitis). 1

Aminoglycosides

Dose aminoglycosides based on adjusted body weight (not total body weight) and monitor serum concentrations; extend dosing intervals in renal impairment. 1

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Important Caveats

Avoid fluoroquinolones when other options are available due to risks of tendinopathy, peripheral neuropathy, and CNS effects; reserve for patients with comorbidities or contraindications to other agents. 3

Do not use macrolide monotherapy in areas with pneumococcal macrolide resistance ≥25%; combination therapy or alternative agents are required. 3

Clindamycin carries increased risk of Clostridioides difficile infection compared to other oral agents for skin infections. 1

Linezolid should not exceed 28 days of therapy due to risks of myelosuppression and peripheral neuropathy; monitor complete blood counts weekly. 1, 4

Daptomycin is inactivated by pulmonary surfactant and should not be used for pneumonia. 1