Laboratory: Clinical Biochemistry
Test Name:
Test Code: PYN
Clinical Information:
Phenytoin is used extensively for seizure control in patients having grand mal epilepsy (major motor), temporal lobe epilepsy or cortical focal seizures. Plasma drug monitoring is used to ensure appropriate therapeutic concentration.
Reference range presupposes a normal serum albumin.  For abnormal albumin (eg. in pre-eclampsia), the phenytoin result should be adjusted before comparing to the reference ranges.
Corrected Phenytoin = Measured Phenytoin
                                  0.9 (albumin/40) + 0.1
The calculation does not pertain to all patients’ conditions.  Albumin concentration is reported along side the phenytoin concentration to facilitate the calculation by the clinician as required.
Alternate Name:  Dilantin
For more information see:
Collection Devices:
Do not use separator gel.
Specimen Required:

Plasma: 2.0 mL

Stability 7 days refrigerated, 12 weeks frozen

Serum: 2.0 mL
Samples must be transferred to an aliquot tube and stored frozen if analysis will not be complete within 48 hours (#110-10-05 Serum / Plasma Separation Procedure & Transport)
Reference Values:
0 - 4 wk:  6-14 mg/L
≥ 5 wk:   10-20

Toxic:       >20                 (mg/L = μg/mL)
Stat or Routine
See Also:
More Information: