Release of gentamicin from acrylic bone cement.

The pharmacokinetics of gentamicin were studied after total hip joint arthroplasties performed with "Palacos R plus gentamicin' in 10 patients. Urine was collected at 12-hour intervals for 15 days after operation, and drainage fluids for 48, 72 or 108 hours. Blood samples were taken 3 and/or 5 hours after prosthesis implantation. High concentrations of gentamicin were found in drainage fluids. Excretion curves in drainage fluids or urine were fitted by a computer-aided design program (SIAM) and the mean curves established. Elimination of gentamicin was biphasic in both cases. The rapid phases had a half-life of 2.97 hours in drainage fluids and 7.16 hours in urine. Half-lives of the slow phases were 13.5 and 47.12 hours, respectively. The mean percentage of total gentamicin released by the two routes was 5.78% of the quantity implanted. The calculated peak blood concentration was 0.12 mg/L. It is concluded that gentamicin concentrations locally reach levels higher than minimum inhibitory concentrations of most of the likely pathogens in patients undergoing total hip joint arthroplasties with "Palacos R plus gentamicin' bone cement. However, as blood concentrations appear to be low, patients may not be protected against systemic infections.