What is the purpose of antibiotic prophylaxis in surgery and when should timing occur?

• A. Cure existing infections after surgery
• B. Reduce surgical site infection; administer within 60 minutes before incision (time varies by agent)
• C. Treat postoperative fever
• D. Prophylaxis should be given after incision

Answer: (B)

Antibiotic prophylaxis in surgery is about preventing infection by ensuring the drug is at effective levels in the tissues at the moment the incision is made. The aim is to have adequate antibiotic exposure right when potential contamination occurs, which reduces the risk of a surgical site infection.

The best way to achieve this is to administer the antibiotic within about 60 minutes before the incision, though the exact timing can vary by agent because infusion times and pharmacokinetics differ. Some drugs with longer infusion times or specific properties may require starting earlier, up to around 120 minutes before incision. In long procedures, redosing may be needed to maintain effective levels throughout the operation.

Prophylaxis is not about curing an existing infection after surgery, nor about treating postoperative fever, and giving it after incision misses the preventive window when bacteria can enter the wound.