Suitability of collection tubes with separator gels for therapeutic drug monitoring.

The purpose of this study was to determine the suitability of four collection tubes containing separation gels for collection of specimens for 15 therapeutic drugs. To blood tubes from drug-free volunteers, selected drugs were added and measured after centrifugation and storage for 6, 24, and 72 h in the collection tube. We found that the Becton Dickinson SST tube extracted phenytoin even with immediate separation of serum. For prolonged storage, the SST tube was unsuitable for quinidine (greater than 24 h) and lidocaine (greater than 6 h); the Monoject Corvac was unsuitable for lidocaine (any storage). Partially filled tubes caused additional errors. Completely filled Terumo Autosep and Monoject Corvac tubes are satisfactory for all drugs tested if serum is removed promptly.