Alterations in gentamicin pharmacokinetics during neonatal exchange transfusion

The effect of double volume exchange transfusion on the pharmacokinetics of gentamicin was studied in 7 neonates undergoing eight transfusions. The procedures were performed an average of 9.6 h following the previous dose of drug and required an average of 0.91 h to complete. Exchange transfusion decreased serum gentamicin concentrations by 18.5 +/- 4.2% and increased the elimination rate for gentamicin by 31.8%. Serum concentrations obtained an average of 3.3 h following the procedure showed a rebound increase in concentration compared to that obtained just at the end of the transfusion (2 cases), no change (1 case) or a decrease compared with the immediate posttransfusion period (5 cases). The results observed in the late posttransfusion period were found to be inversely related (r = -0.78) to the number of doses received by the patient prior to the procedure. A one-compartment pharmacokinetic model was found to be adequate in predicting the amount of drug removed by the procedure while a two-compartment model best described the posttransfusion alteration in elimination kinetics.