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Phenytoin
Test Code713
CPT Codes
80185
Preferred Specimen
1 mL serum collected in a red-top tube (no gel)
Minimum Volume
0.2 mL
Other Acceptable Specimens
Plasma collected in: Sodium heparin (green-top) tube, lithium heparin (green-top) tube, or EDTA (lavender-top) tube
Instructions
Collect as trough just prior to next dose. For patients receiving fosphenytoin therapy, collect as trough at least 2 hours after IV infusion or at least 4 hours after IM injection.
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 5 days
Refrigerated: 10 days
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Serum separator tube (SST)
Methodology
Immunoassay (IA)
Setup Schedule
Set up: Mon-Thurs p.m., Fri, Sat evenings; Report available: Next day
Reference Range
10.0-20.0 mg/L
Clinical Significance
Phenytoin is an anticonvulsant hydantoin used for the treatment of generalized tonic-clonic (grand mal) and complex partial seizures. Phenytoin is also used for prophylaxis in neurosurgical procedures. Phenytoin levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity.
Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153