Topic overview

Start with the big picture

Prophylaxis is appropriate when evidence indicates that prevention benefits outweigh potential harms. The choice should be guided by the organisms expected in that setting, with preference for narrow-spectrum, bactericidal, low-toxicity and cost-effective agents. Avoiding unnecessary use—including in low-risk clean procedures—helps limit resistance. Surgical prophylaxis is a central example: the lesson addresses administration before incision, redosing during some operations, and stopping prophylaxis after surgery rather than extending it without benefit. It also surveys non-surgical situations, including prevention related to endocarditis risk, childbirth, close exposure to meningococcal disease, and selected infectious or immune-risk conditions. Together, these examples show why prophylaxis depends on the specific exposure and patient context, not a single universal regimen.