Pharmacokinetics of cefazolin applied topically to the surgical wound

Topical application of antibiotics is used in the prophylaxis of postoperative surgical infections. However, whether topically applied antibiotics remain primarily in the surgical wound fluid or are systemically absorbed is uncertain. The pharmacokinetics of topically applied cefazolin were studied in a canine model that allowed simultaneous determination of serum and wound fluid antibiotic concentrations. Topical administration of cefazolin resulted in high antibiotic concentrations in the wound fluid for prolonged periods and rapid systemic absorption. Bioavailability after topical administration was 95%. Within 1 hour, the serum concentrations after topical administration equaled the serum concentrations after intravenous administration, and the concentration time curves declined in parallel. In wound fluid, the mean time above the susceptibility break point minimum inhibitory concentration after topical administration of cefazolin was 5.76 hours compared with the estimated time above the minimum inhibitory concentration of 2.55 hours after intravenous administration.