Background/Aims: Multiple organ failure alters the dosage of drugs during hemofiltration. To separate factors, we utilized in vitro hemofiltration to investigate different blood flows, protein concentrations and intracellular drug partition with the FH77H polyamide membrane. Methods: One liter of warm heparinized fresh human blood was hemofiltrated in two series: (1) with digoxin, netilmycin, phenobarbital, ceftriaxone and teicoplanin, and (2) with amikacin, theophylline, ceftazidim, phenytoin and vancomycin and, in addition, with cell-free fresh frozen plasma. Results: The increased volumes of distribution of aminoglycosides and theophylline were a combined result of partition into cells and adsorption into the filter membrane. The deviations of drug sieving from predicted values were due to different affinities of the drugs on whole blood binding sites. Conclusion: The in vitro composition of drugs and blood improved the detection of factors that influence drug elimination during hemofiltration. The FH77H polyamide hemofilter facilitates more precise predictions of drug dosages by low adsorption rates to the membrane.