Antibiotic prophylaxis in vascular surgery: pharmacokinetic study of four commonly used cephalosporins.

Plasma levels of antibiotics often do not correlate well with their tissue levels. To determine optimal antibiotic coverage for prophylactic effect in vascular surgery, we studied the tissue pharmacokinetics of four cephalosporins in dogs: cefazolin, cefoxitin, cefamandole, and moxalactam for 3 hours after a single (25 mg/kg) intravenous injection. The minimal inhibitory concentration (MIC) of these antibiotics for the three most common pathogens involved in graft infections (Staphylococcus aureus, S. albus, and Escherichia coli) and their tissue concentration (TC) in the plasma, muscle, subcutaneous tissue, and aortic wall were assayed. The data are presented as TC/MIC ratio. Cefoxitin and moxalactam failed to achieve an effective therapeutic TC/MIC ratio (greater than 10) for S. aureus and S. albus in all the tissues studied whereas cefoxitin and cefamandole were above therapeutic levels. All antibiotics achieved an effective therapeutic ratio against E. coli, but cefamandole performed better (p less than 0.05) than cefoxitin; the latter reached effective levels at 3 hours. Cefamandole attained the most effective bioactive aortic tissue levels when the three most common pathogens were considered together and should therefore be considered as an antibiotic agent of choice for prophylaxis in vascular surgery.