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HelpTest Code PTN Phenytoin
Useful For
Phenytoin (5,5-diphenylhydantoin) is one of the most widely prescribed drugs for the treatment of seizure disorders. It is considered one of the drugs of choice for generalized major motor (grand mal epilepsy) and focal seizures.
Synonyms/Keywords
Dilantin, DPH, Diphenylhydantoin
Specimen Requirements
| Fasting Required | Specimen Type | Preferred Container/Tube | Acceptable Container/Tube | Specimen Volume | Specimen Minimum Volume (allows for 1 repeat) |
Pediatric Minimum Volume (no repeat) |
|---|---|---|---|---|---|---|
| No | Serum | Serum Separator Tube (SST) | Red Top Tube (RTT) | 0.5 mL | 0.2 mL | 0.4 mL whole blood |
Collection/Processing Instructions
- Indicate time of collection.
- Separate serum from cells within 1 hour of collection if using RTT.
- Serum must be removed from gel within 24 hours of collection.
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Room Temperature | 8 hours |
| Refrigerate | 7 days | |
| Frozen | 30 days |
Test Information
Collect trough specimen just prior to next dose.
Half Life (adult): 70-100 hours. Time to steady state (adult): 15-25 days. Time to peak level: 4-10 hours.
Coadministration with drugs that acidify urine (valproic acid, salicylate) will decrease excretion.
Reference Range Information
| Performing Location | Reference Range |
|---|---|
| All Performing Sites | Therapeutic: 10.0 20.0 g/mL See Critical Value List for list of current critical values |
Marshfield Labs Performing Department
Marshfield Labs Chemistry
Performing Information
| Performing Location | Day(s) Test Performed | Analytical Time | Methodology/Instrumentation |
|---|---|---|---|
| Marshfield | Monday through Sunday | Less than 2 hours | Emit* 2000 Rate Assay/Beckman AU |
CPT Codes
| CPT | Modifier (if needed) |
Quantity | Description | Comments |
|---|---|---|---|---|
| 80185 |
Outreach CPT Codes
| CPT | Modifier (if needed) |
Quantity | Description | Comments |
|---|---|---|---|---|
| 80185 |
Ordering Applications
| Ordering Application | Description |
|---|---|
| Cerner | Phenytoin Level Total |