Stability of therapeutic drugs in serum collected in vacutainer serum separator tubes containing a new gel (SST II)

The stability of therapeutic drugs in sera collected in Becton-Dickinson Va cutainer serum separator SST tubes has been well studied. Although most the rapeutic drugs are stable, certain drugs such as phenytoin, carbamazepine, and phenobarbital decrease in concentrations over a long storage time. To c ircumvent this problem, Becton-Dickinson devised a new gel formulation. The authors studied the stability of 14 commonly monitored drugs in sera when stored on the new gel of the SST II tubes and compared the concentrations o f drugs in sera stored in plain tubes (no gel), those stored in the old SST tubes, and those stored in the SST II tubes containing a new serum separat or gel, The concentrations of most drugs studied did not decline even after 24 hours of storage in SST II tubes. After storage for 7 days in SST II tu bes, the concentration of carbamazepine declined by 10% and that of phenyto in decreased by 4%. This is a significant improvement over the existing tub e, where concentrations of several drugs declined with prolonged storage. T he authors conclude that new SST II tubes are effective in collecting blood for therapeutic drug monitoring.