Heterogeneity in gentamicin clearance between high-efficiency hemodialyzers.

Gentamicin is frequently prescribed for treatment of gram-negative infections in patients on dialysis. The amino-glycoside is renally excreted; therefore, dosage modifications are required in patients on hemodialysis. The introduction of short-duration dialysis using high-efficiency hemodialyzers requires that the dialysance of gentamicin be re-examined. We recently demonstrated that high-efficiency dialyzers have a superior gentamicin clearance as compared with conventional dialyzers. In this study we examined the dialysance of gentamicin in two high-efficiency dialyzers using a randomized, controlled, cross-over design. Despite a comparable amount of dialysis (Kt/V urea), rate of dialysis (K/V urea), and ultrafiltration, there were significant differences noted in gentamicin removal between the high-efficiency cuprammonium rayon and polysulfone dialyzers. Furthermore, the amount of dialysis (Kt/V urea) could predict the fractional gentamicin clearance for the TAF 175L dialyzer (Terumo Corp, Somerset, NJ) and may be useful in the initial planning of gentamicin therapy. In addition, since gentamicin is a middle molecule (molecular weight, 500 to 2,000 d), the study suggests a superior middle molecule clearance of cuprammonium rayon dialyzer compared with a high-efficiency polysulfone dialyzer. The substantial heterogeneity in gentamicin clearance, even between dialyzers of the same class, emphasizes the importance of monitoring drug levels in hemodialysis patients receiving this drug.