Concentrations of cefazolin in human skeletal muscle

Tissue concentrations of cefazolin were measured in 18 patients undergoing urological operations. Specimens of skeletal muscle and blood were taken simultaneously at predetermined intervals. The concentrations in serum and homogenized skeletal muscle were determined by means of the agar well diffusion method. A comparison of standard curves obtained with phosphate buffer solution and the supernatant of muscle homogenate revealed no substantial binding of cefazolin to the supernatant of muscle homogenate. Because of methodological difficulties in determining the different compartments of a tissue specimen concentrations in tissue were not corrected. Within two hours after a short infusion (25 min.) of 2 g of Cefazolin in muscle tissue a peak concentration of 20 mug/g was reached. A tissue level above 10 mug/g maintained for three hours. This concentration is high enough to inhibit nearly all strains of E. coli, Klebsiella, Salmonella, Shigella and a large part of Proteus mirabilis, whereas nearly all gram-positive bacteria are inhibited at a lower concentration.