Guidelines
Antibiotic Dosing

Antibiotic Dosing

Drug Dosing

For antimicrobials with short half-lives, intra-operative dosing is recommended for patients with normal renal function if:

  • prolonged surgical procedure (> 2 half-lives of the antimicrobial) OR
  • major blood loss (>1.5L). If massive blood loss occurs, a second dose should be given promptly. See Table below:
Prophylactic Antibiotic Half life (hours) Re-dosing interval*
ceFAZolin 1.2-2.2 Q4h
clindamycin 2-4 Q6h
aminoglycoside 2-3 N/A**
metroNIDAZOLE 6-8 N/A**
vancomycin 4-8 N/A**

* Recommended re-dosing interval from time of administration of the pre-op dose

** Not applicable (N/A) based on typical case length; for unusually long procedures, redosing may be needed except for aminoglycoside dosed at 5 mg/kg

Antimicrobial prophylaxis for patients with renal or hepatic dysfunction often does not need to be modified when given as a single dose pre-operatively

  • Aminoglycoside 5 mg/kg (extended interval dose) provides at least 24 hours of antimicrobial coverage.
  • Tobramycin is an acceptable alternative for the indication of surgical prophylaxis in the event that gentamicin is not available. Dose based on ideal body weight (IBW), unless actual body weight (ABW) is greater than 20% above IBW, then use dosing body weight, calculated as follows:

Ideal body weight (males)

  • 50 kg + (0.92 x cm above 150 cm) OR
  • 50 kg + (2.3 kg x inches above 60 inches)

Ideal body weight (females)

  • 45.5 kg + (0.92 x cm above 150 cm) OR
  • 45.5 kg + (2.3 kg x inches above 60 inches)

Dosing body weight

  • IBW + 0.4 (ABW – IDW)

Vancomycin 15 mg/kg based on patient’s ABW and rounded to the nearest 250 mg

  • Conclusive recommendations for weight-based dosing for antimicrobial prophylaxis in obese patients cannot be made because data demonstrating clinically relevant decreases in SSI rates from the use of such dosing strategies instead of standard doses are not available in the published literature.
  • Considering the low cost and favourable safety profile of ceFAZolin, the minimum dose should be 2 g. Increasing the dose to 3 g for those weighing 120 kg or more can easily be justified. For simplification, these guidelines recommend 2 g ceFAZolin doses for all adult patients

Note: This guideline is intended for adults only. Pediatric dosing provided in table below: Please note:

  • This table applies only to pediatric patients weighing 40kg or less
  • The maximum pediatric dose should not exceed the usual adult dose
  • This table does not specifically address new born infants
Antibiotic Recommended Dose
ampicillin 50 mg/kg
ceFAZolin 30 mg/kg
cefTRIAXone 50-70 mg/kg
ciprofloxacin 10 mg/kg
clindamycin 10 mg/kg
aminoglycoside 2.5 mg/kg
metroNIDAZOLE 15 mg/kg
piperacillin-tazobactam see below*
vancomycin 15 mg/kg

*Infants 2-9 months: 80 mg/kg of the piperacillin component. *Children greater than 9 months and less than or equal to 40kg: 100 mg/kg of the piperacillin component