Phenytoin

Code:
PHYN

Sample Type:

Serum (Gold Top)

Minimum volume: 1 mL

Ref Ranges/Units:

Therapeutic range 5 – 20 mg/L

Results >25 mg/L will be phoned to the requesting clinician.

Turnaround:

Same Day (60 minutes from receipt for Urgent Samples)

Stability:

4 days capped at 2‑8°C or 15‑25°C  
1‑2 months capped at -20°C 

Special Precautions/Comments:

Trough sample recommended (blood drawn immediately before scheduled dose).  

Additional Information:

Phenytoin is a widely prescribed anti-convulsant used in the treatment of major motor (grand mal epilepsy) and focal seizures.  

High doses of phenytoin (>25 mg/L) are associated with toxicity. Therapeutic drug monitoring allows the optimal therapeutic dose to be achieved by avoiding both subtherapeutic and toxic levels. 

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