Stability of drug concentrations in plasma stored in serum separator blood collection tubes.

The stability of therapeutic concentrations of 11 drugs (amikacin, carbamazepine, digoxin, gentamicin, lithium, methotrexate, phenobarbital, phenytoin, quinidine, theophylline, tobramycin) and two trace elements (copper and zinc) in plasma stored in serum separator ("Corvac" brand) blood collection tubes was investigated over a 1 week period of storage in the refrigerator. No significant change in concentration was noted for any analyte during the study period. Concentrations were also not significantly different from those observed during concurrent storage of the same plasma samples in nonserum separator ("Vacutainer" brand) blood collection tubes.