Abstract
The effects of commercially available serum separators on measured serum drug concentrations were examined. Blood samples were drawn into Vacutainer Serum Separator Tube (SST) and tubes without the separator gel (Venoject Red Top tube) from patients taking antiepileptic drugs. The serum levels of phenytoin, phenobarbital, carbamazepine, and valproate were then determined by fluorescence polarization immunoassay procedure. A significant decrease in measured concentrations of phenytoin and phenobarbital was observed when SST was used.
Three commercially available serum separators, SST, Venoject AutoSep, and Auto Iso-Filter were compared for their effects on the measured concentrations of phenytoin using blood samples containing the known amounts of phenytoin. All of these separators caused decreases in drug concentrations, but the extents of the decreases were different among the three separators. The most remarkable effect was found in Auto Iso-Filter, followed by SST. The effect of AutoSep was slight. It was found that the decrease in the measured drug concentrations was greatly influenced by the duration of exposure to the separators and the volume of blood samples.
The similar effects of the separators were also found in lidocaine.
These results suggested that the serum separator must be carefully chosen before the use for the determination of serum levels of the drugs.
