Elimination of ampicillin and gentamicin by hemofiltration

Elimination of ampicillin and gentamicin by hemofiltration was measured in 5 and 4 patients, respectively, being treated for end stage renal failure. Serum half-life time of ampicillin after a single I.V. dose of 2 g, was found to be 2.97 +/- 0.73 h, and the filtrate concentrations declined parallel to the serum ampicillin levels, as was to be expected. The serum half-life time after a single I.V. dose of 1 mg/kg body weight gentamicin was 3.26 +/- 0.42 h, and considerably shorter than T/2 of gentamicin in conventional hemodialysis, while the filtrate concentrations increased paradoxically with declining serum levels. This could be explained by binding of this aminoglycoside to the polyacrylnitril membrane of the RP 6 dialyser used for hemofiltration.