Influence of hemodialysis on gentamicin pharmacokinetics, removal during hemodialysis, and recommended dosing.

BACKGROUND AND OBJECTIVES: Aminoglycoside antibiotics are commonly used in chronic kidney disease stage 5 patients. The purpose of this study was to characterize gentamicin pharmacokinetics, dialytic clearance, and removal by hemodialysis and to develop appropriate dosing strategies. Design Setting, Participants, and Measurements: Eight subjects receiving chronic, thrice-weekly hemodialysis with no measurable residual renal function received gentamicin after a hemodialysis session. Blood samples were collected serially, and serum concentrations of gentamicin were determined.
RESULTS: Median (range) systemic clearance, volume of distribution at steady state, and terminal elimination half-life were 3.89 ml/min (2.69-4.81 ml/min), 13.5 L (8.7-17.9 L), and 39.4 h (32.0-53.6 h), respectively. Median (range) dialytic clearance, estimated amount removed, and percent maximum rebound were 103.5 ml/min (87.2-132.7 ml/min), 39.6 mg (19.7-43.9 mg), and 38.7% (0%-71.8%), respectively. Gentamicin dialytic clearance was statistically significantly related to creatinine dialytic clearance (r(2) = 0.52, P = 0.04), although this relationship is not likely to be strong enough to serve as a surrogate for gentamicin monitoring. The pharmacokinetic model was used to simulate gentamicin serum concentrations over a one-wk period.
CONCLUSIONS: In clinical situations where gentamicin is used as the primary therapy in a patient receiving hemodialysis with a CAHP hemodialyzer, conventional doses after each dialysis session are not as efficient at achieving treatment targets as predialysis dosing with larger doses.