[Decrease in the concentration of tobramycin, vancomycin and phenobarbital in administration with infusion filter].

To assess the loss of drugs to in-line filters, concentrations of tobramycin, vancomycin, and phenobarbitone were determined in vitro in samples recovered upstream and downstream of the filter. Binding of the drugs to new filters was higher than to used filters. With bolus administration, the concentrations of vancomycin and phenobarbitone were reduced by 1% when using old filters and by 4% when using new filters. Tobramycin concentrations were reduced by 7 and 12%, respectively. With continuous administration of the drugs, binding was highest during the first half hour. Differences between new and used filters were also seen with continuous administration: The cumulative loss was 5% higher with new than with old filters. This difference in binding between filters may stem from a saturation of free binding sites. Tobramycin showed the highest binding to the in-line filter. The extent of adsorption of tobramycin to intravenous filters may be considered moderately important in adult patients. The adsorption of vancomycin and phenobarbitone is not clinically relevant in adult patients.