What are the typical doses and maximum doses of common antibiotics, such as ciprofloxacin (Cipro), levofloxacin (Levaquin), and amoxicillin-clavulanate, in a 24-hour period?

Common Antibiotic Dosing in 24 Hours with Maximum Doses

Fluoroquinolones

Ciprofloxacin

• Standard dose: 500-750 mg orally twice daily (total daily dose: 1000-1500 mg) 1
• Intravenous dose: 400 mg every 12 hours (total daily dose: 800 mg) 1
• Maximum daily dose: 1500 mg 1
• For severe infections such as necrotizing soft tissue infections or pneumonia with Pseudomonas aeruginosa, the higher end of dosing (750 mg twice daily orally or 400 mg every 12 hours IV) is recommended 1
• For anthrax prophylaxis: 500 mg orally twice daily for 60 days 1

Levofloxacin

• Standard dose: 500 mg once daily (orally or IV) 1, 2
• High-dose regimen: 750 mg once daily (orally or IV) 1, 2
• Maximum daily dose: 750 mg 1, 2
• The 750 mg dose is preferred for severe community-acquired pneumonia, complicated infections, and Pseudomonas coverage 1
• Oral and IV formulations are bioequivalent and interchangeable 2
• Steady-state concentrations are reached within 48 hours of once-daily dosing 2

Beta-Lactam/Beta-Lactamase Inhibitor Combinations

Amoxicillin-Clavulanate (Oral)

• Standard dose: 875 mg/125 mg twice daily (total amoxicillin: 1750 mg/day) 1, 3
• Alternative dose: 500 mg/125 mg three times daily (total amoxicillin: 1500 mg/day) 1, 3
• High-dose amoxicillin for resistant organisms: 3000-4000 mg/day 1, 4
• Maximum daily dose: 4000 mg of amoxicillin component 4
• For animal bites: 875 mg/125 mg twice daily 1
• The maximum dose of 4 grams per day applies regardless of patient size or weight 4

Ampicillin-Sulbactam (IV)

• Standard dose: 1.5-3.0 g every 6-8 hours 1
• Maximum daily dose: 12 g (administered as 3 g every 6 hours) 1
• Used for animal/human bites and mixed soft tissue infections 1

Piperacillin-Tazobactam (IV)

• Standard dose: 3.375 g every 6-8 hours 1
• High-dose regimen: 4.5 g every 6 hours 1
• Maximum daily dose: 18 g (administered as 4.5 g every 6 hours) 1
• Preferred for Pseudomonas aeruginosa and mixed necrotizing infections 1

Cephalosporins

Cefazolin (IV)

• Standard dose: 1-2 g every 8 hours 1
• Maximum daily dose: 6 g (administered as 2 g every 8 hours) 1
• Used for methicillin-susceptible Staphylococcus aureus infections 1

Ceftriaxone (IV)

• Standard dose: 1-2 g every 12-24 hours 1
• Maximum daily dose: 4 g (administered as 2 g every 12 hours) 1
• For pneumonia: typically 2 g once daily 1
• For necrotizing infections: 1 g every 12 hours 1

Cefepime (IV)

• Standard dose: 2 g every 8-12 hours 1
• Maximum daily dose: 6 g (administered as 2 g every 8 hours) 1
• Preferred for Pseudomonas aeruginosa and resistant gram-negative infections 1

Cefotaxime (IV)

• Standard dose: 1-2 g every 6-8 hours 1
• Maximum daily dose: 8 g (administered as 2 g every 6 hours) 1
• Used for severe pneumonia and resistant Streptococcus pneumoniae 1

Carbapenems

Meropenem (IV)

• Standard dose: 1 g every 8 hours 1
• Maximum daily dose: 3 g (administered as 1 g every 8 hours) 1
• Preferred for necrotizing infections and multidrug-resistant gram-negative organisms 1

Imipenem-Cilastatin (IV)

• Standard dose: 500 mg to 1 g every 6-8 hours 1
• Maximum daily dose: 4 g (administered as 1 g every 6 hours) 1
• Used for severe mixed infections and Pseudomonas coverage 1

Ertapenem (IV)

• Standard dose: 1 g once daily 1
• Maximum daily dose: 1 g 1
• Does not cover Pseudomonas aeruginosa 1

Glycopeptides

Vancomycin (IV)

• Standard dose: 15-20 mg/kg every 8-12 hours 1
• Maximum single dose: typically 2 g per dose 1
• Total daily dose: 30-40 mg/kg/day 1
• Loading dose should be considered for severe infections 1
• Serum levels should be monitored to maintain trough concentrations of 15-20 mcg/mL for serious infections 1

Important Clinical Considerations

Common Pitfalls

• Do not exceed 4 g/day of oral amoxicillin regardless of patient weight 4
• Confusing oral and IV maximum doses: IV ampicillin can reach 12 g/day for endocarditis, but oral amoxicillin maximum remains 4 g/day 4
• Fluoroquinolone dosing errors: Levofloxacin 750 mg is once daily, not twice daily like ciprofloxacin 1, 2
• Renal adjustment required: Most antibiotics require dose reduction in renal impairment, particularly fluoroquinolones, vancomycin, and beta-lactams 2, 5, 6

Dosing Adjustments in Critical Illness

• Loading doses are independent of renal function and should not be reduced in critically ill patients 5, 6
• Hydrophilic agents (beta-lactams, aminoglycosides) may require increased doses in early sepsis due to expanded volume of distribution 5, 6
• Time-dependent antibiotics (beta-lactams) benefit from extended or continuous infusions to maximize time above MIC 6
• Concentration-dependent antibiotics (fluoroquinolones, aminoglycosides) should be given as single daily doses to maximize peak concentrations 6