Background: Vancomycin (VCM) is eliminated mainly by diafiltration under continuous hemodiafiltration (CHDF), but the contribution of adsorption to CHDF clearance (CL CHDF ) of VCM using a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST) or a polymethylmethacrylate (PMMA) membrane is unknown. This study sought to investigate the contribution of diafiltration and adsorption to the CL CHDF of VCM using AN69ST and PMMA membranes in vitro.Methods: An in vitro CHDF circuit model was developed. The initial concentration of VCM was 50 μg/mL and human serum albumin (HSA) was prepared at a concentration of 0, 2.5, or 5.0 g/dL. The effluent flow rate (Qe) was set at 800, 1500, or 3000 mL/h. The CL CHDF , diafiltration rate, and adsorption rate of VCM were calculated.Results: Total CL CHDF of VCM using the AN69ST membrane increased and decreased with increasing Qe and HSA concentration, respectively. Diafiltration and adsorption rates were 82.1 ± 9.8% and 12.1 ± 6.1% under all conditions, respectively. Total CL CHDF using the PMMA membrane increased with increasing Qe. Diafiltration and adsorption rates were 89.2 ± 20.4% and 4.6 ± 17.0% under all conditions, respectively. The observed CL CHDF values significantly correlated with the predicted CL CHDF , calculated according to a previous study as the product of Qe and the plasma unbound fraction.Conclusions: Diafiltration predominantly contributed to CL CHDF of VCM using AN69ST and PMMA membranes. When diafiltration rather than adsorption mainly contributes to the CL CHDF of VCM, the CL CHDF could be predicted from the Qe and HSA concentration, at least in vitro.

Background In the treatment of sepsis, continuous hemodiafiltration (CHDF) and the administration of antibiotics such as teicoplanin (TEIC) are frequently performed in parallel. We aimed to clarify the factors influencing the CHDF clearance (CLCHDF) of TEIC using a polymethylmethacrylate (PMMA) membrane or a polyacrylonitrile and sodium methallyl sulfonate copolymer membrane coated with polyethylenimine (AN69ST). We also investigated whether the adsorption of TEIC onto the hemofilters inhibits the adsorption of interleukin (IL)‐6 onto the membranes. Methods TEIC, human serum albumin (HSA), and IL‐6 were incubated with pieces of hemofilter membranes and adsorption rates were calculated. The CLCHDF, diafiltration rate, and adsorption rate of TEIC were calculated using an in vitro CHDF circuit model. Results The adsorption rates of TEIC onto the pieces of PMMA and AN69ST membranes ranged from 15.0% to 100% and from −10% to 5%, respectively. The adsorption rate of IL‐6 was similar with or without TEIC. The CLCHDF and adsorption rate of TEIC under PMMA‐CHDF depended on HSA, but not on effluent flow rate (Qe). The CLCHDF under AN69ST‐CHDF depended on HSA and Qe. The observed CLCHDF under AN69ST‐CHDF was similar to the predicted value (the product of Qe and the plasma unbound fraction). The observed CLCHDF under PMMA‐CHDF was 2.0–7.8 times greater than the predicted value. Conclusions Adsorption mainly contributes to the CLCHDF of TEIC using PMMA membranes, whereas diafiltration mainly contributes to the CLCHDF of TEIC using AN69ST membranes. TEIC adsorption might not affect the adsorption of IL‐6 onto PMMA membrane.