Commentary: PDF OnlyEffect of Serum Separator Blood Collection Tubes on Drug ConcentrationsQuattrocchi, Frank; Karnes, H. Thomas*; Robinson, J. Daniel†; Hendeles, Leslie‡Author Information Department of Pharmacy Services, Wuesthoff Memorial Hospital, Rockledge, Florida; *Department of Pharmaceutics, and †Departments of Pharmacy and Medicine and Family Practice Pharmacokinetic Service; and ‡Departments of Pharmacy and Pediatrics and Pediatric Pharmacokinetic Consultation Service, College of Pharmacy, University of Florida, Gainesville, Florida Therapeutic Drug Monitoring: September 1983 - Volume 5 - Issue 3 - p 359-362 Buy Abstract Using the EMIT® assay, we tested clinical samples from patients receiving 12 commonly monitored drugs to evaluate the effect of serum separator gel contained in serum separator blood collection tubes (SST) (Becton-Dickinson). There were significant concentration decreases for lidocaine, pentobarbital, and phenytoin. In vitro experiments demonstrated that this effect on phenytoin was dependent on time of exposure to the gel and volume of whole blood, but was not dependent on the presence of red blood cells or initial concentration. Bias attributed to the use of SST could interfere with the usefulness of clinical results at the upper and lower limits of the therapeutic range. This problem can be minimized by processing samples of at least 2 ml within 1 h. © Lippincott-Raven Publishers.