Pharmacokinetics of topical gentamicin in total hip arthroplasty

Two different ways of administering topical gentamicin were examined in patients undergoing total hip arthroplasty. 160 mg gentamicin, dissolved in isotonic saline, was instilled into the wounds of five out of ten patients. In the other five patients, the components of the prostheses were inserted by means of gentamicin-containing cement, 0.5 g per 40 g powder. Both the serum concentrations and the wound concentrations of gentamicin were determined constantly during the postoperative period. The average half-lives of gentamicin in the surgical wounds of the two groups of patients were found to be 3½ and 25h, respectively. The average wound concentration was found to be higher than the minimum inhibitory concentration for staphylococci and aerobic Gram-negative rods for 18 and 11 h, respectively, in the group of patients treated with gentamicin solution compared with 160 and 67 h, respectively, in the group treated with the gentamicin-containing cement.