Phenytoin, Total, Serum/Plasma


Phenytoin is an anticonvulsant used in the management of tonic-clonic, general motor and focal seizures, as well as those related to head trauma or neurosurgery. Increased free phenytoin levels result from hypoalbuminaemia, pregnancy, renal failure, hepatic disease and uncontrolled diabetes. Decreased free phenytoin levels result from hyperalbuminaemia.


Measurement of phenytoin level is used to monitor the dose of the drug in order to avoid its toxic effect and maintain the desired therapeutic effect.

Sample Type, Quantity & Conditions

1 ml Serum 1 ml K2, K3, Na2-EDTA, Li, Na-Heparin, Sodium Citrate, or Potassium Oxalate Plasma Stability: 2 Days at 20-25 °C 8 Days at 2-8 °C 5 Months at -20 °C

Special Precautions

Collect sample at least 2 Hrs after completion of IV dose or 4 Hrs after IM dose. Avoid grossly haemolysed samples.

Normal Range

Therapeutic Range: 10-20 μg/mL 40-79 μmol/L Toxic Level: > 20 μg/mL > 79 μmol/L Panic Values: > 30 μg/mL

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