When should perioperative antibiotic prophylaxis be given for most procedures?

• A. Within 60 minutes before incision (within 120 minutes for vancomycin or fluoroquinolones)
• B. After incision
• C. 24 hours prior
• D. Only if infection risk high

Answer: (A)

The key idea is to have adequate antibiotic levels in the tissues at the moment the incision is made so bacteria introduced during surgery are immediately challenged. For most procedures, that means giving the prophylactic antibiotic within an hour before the incision. When vancomycin or fluoroquinolones are used, their longer infusion times require administration within about two hours before the incision to ensure peak tissue concentrations align with the cut. Giving the antibiotic after the incision misses the critical window and is less effective at preventing contamination. Administering it 24 hours before isn’t appropriate for prophylaxis and can raise risks without added benefit. Prophylaxis timing isn’t limited to scenarios labeled as high infection risk; the standard approach aims to protect the wound at the moment of incision.