Pathology Handbook

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Phenytoin

Alternative Names:

Dilantin

Laboratory:

Clinical Biochemistry

Test Code:

PTN

Specimen Types:

Blood

Container Types:

Lithium Heparin (with Gel)
SST

Adults Volume or Mass:

5 mL

Minimum/Paediatric Volume or Mass:

1 mL

Collection & Request Instructions:

Collect Pre-dose.

Transport Instructions between Sites and/or Laboratories:

RoomTemp within Alfred/Esky from External sites

Assay Frequency:

24/7

MBS Rebatable:

Yes

MBS Item No.:

66800

Additional Notes:

Therapeutic Range: 10.0 - 20.0 mg/L

Critical results notification: 30.0 mg/L

Please note: from 01/10/2024 units have changed from umol/L to mg/L.

To convert: mg/L x 3.97 = umol/L

Therapeutic Range Source: Alinity c Phenytoin Reagent kit insert, July 2018

Measured (Total) Phenytoin consists of "(protein) bound" and "free" (pharmaceutically active) drug. Where plasma albumin is reduced, calculated free phenytoin may be requested to provide a better indication of possible drug toxicity.