| Test Name: | Phenytoin, Free |
| Epic Order Code: | LAB32 | | |
| CPT Code: | 80186 | | |
| Specimen(s) Type: | Serum | | |
| Acceptable Container(s): |  Top is red. |
| Testing Schedule: | 24 hrs/day, 7 days/week |
| Turn Around Time: | STAT: 1 hour | | |
| | Routine: 2 hours | | |
| Collection Information: | No special patient preparation is required. Obtain specimen by standard collection procedures. |
| Transport Information: | Deliver to lab immediately. All specimens must be signed into the laboratory. |
| Reference Clients: | If unable to deliver to the lab within 1 hour, centrifuge the specimen and remove serum from the red cells. Store and transport at 2-8° C. Specimen must be received in the lab within 24 hours. |
| Causes for Rejection: | Improperly labeled, incorrect container, contaminated, insufficient quantity, incorrect/delay in transport. |
| Reference Range: | 1.0 - 2.0 µg/mL |
| | Critical: > 3 µg/mL |
| Additional Information: | Due to the observed cross-reactivity of this assay with fosphenytoin, it is recommended that specimens be collected at least 2 hours after an intravenous dose and at least 4 hours after an intramuscular dose of fosphenytoin. |