Phenytoin

CPT Code: 80185
Order Code: 713
ABN Requirement: No
Alternative Name(s): Dilantin®, Hydantoin
Specimen:
Preferred: serum
Acceptable: plasma
Volume:  1.0 mL
Minimum Volume:  0.2 mL
Container:
Preferred: R, red-top tube (no gel)
Acceptable: L, lavender-top tube, EDTA or Gn, green-top tube, sodium heparin or lithium heparin

Collection:

Serum:

  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. Do not shake.
  3. Allow blood to clot 30 minutes.
  4. Centrifuge specimen for 10 minutes.
  5. Aliquot serum into transport tube labeled as “Red Top Serum” and cap tightly. Discard original tube.

EDTA Plasma:

  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 10 times immediately after draw. Do not shake.
  3. Centrifuge specimen for 10 minutes.
  4. Aliquot plasma into transport tube labeled as “EDTA Plasma” and cap tightly. Discard original tube.

Patient Preparation: Collect as a trough just prior to next dose. For patients receiving fosphenytoin therapy, collect as a trough at least 2 hours after IV infusion or at least 4 hours after IM injection.

Transport: Store serum or EDTA plasma at 2°C to 8°C after collection and ship the same day per packaging instructions included with the provided shipping box.

Stability:

Ambient (15-25°C): 5 days
Refrigerated (2-8°C): 10 days
Frozen (-20°C): 30 days

Causes for Rejection: Serum separator tube (SST)

Methodology: Immunoassay (IA)

Turn Around Time:  2 to 3 days

Reference Range:

Analyte Reference Range (mg/L)
Phenytoin 10.0-20.0

Priority Values:

Analyte Priority 1 Value (mg/L)
Phenytoin ≥40.0

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.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.