Phenytoin, Free and Total, Serum
Also known as: Dilantin-125®, Dilantin®, Free and Total Phenytoin, Phenytek®
Use
Evaluate toxicity; monitor therapeutic levels
Special Instructions
Collect the specimen just prior to the next dose of phenytoin. Serum or plasma must be separated from cells within 45 minutes of collection. Transfer the separated serum or plasma to a plastic transport tube. Avoid using gel-barrier tubes due to drug absorption potential. Specimens should be sent in transport tubes after separation.
Limitations
The use of gel-barrier tubes is discouraged due to potential slow absorption of the drug by the gel, which may result in clinically significant decreased drug levels measured. Hemolysis or lipemic samples may be rejected due to potential interference with the assay.
Methodology
Immunoassay
Biomarkers
LOINC Codes
- 34540-5
- 3968-5
- 3969-3
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
3 mL
Minimum Volume
2.3 mL
Container
Red-top tube or green-top (heparin) tube. Do not use a gel-barrier tube.
Collection Instructions
Transfer separated serum to a plastic transport tube.
Patient Preparation
Collect specimen just prior to next dose.
Storage Instructions
Specimens are stable at room temperature, refrigerated, or frozen for up to 14 days. Stable through 3 freeze/thaw cycles.
Causes for Rejection
Gel-barrier tube; hemolysis; lipemia
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |
Other tests from different labs that may be relevant