Overview of Phenytoin
What is Phenytoin?
Why is Phenytoin done?
The Phenytoin Test is performed:
· To establish the therapeutic dosage for phenytoin in the blood
· To monitor phenytoin levels at regular intervals to maintain therapeutic concentration after starting treatment
· To check for phenytoin toxicity, if toxicity symptoms appear
What does Phenytoin Measure?
The Phenytoin Test measures the levels of phenytoin in blood.
Phenytoin is a drug used mainly for the treatment of epileptic seizures. It is also used to treat convulsions and seizures caused due to neurosurgery. It may be prescribed along with other anticonvulsant medications like phenobarbital. Phenytoin, taken orally is absorbed in the intestinal tract and goes into the blood. In blood, most of it gets bound to plasma proteins like albumin and only a small portion remains free. Only the free phenytoin remains metabolically active and the phenytoin-protein complex remains inactive. Phenytoin blocks the excessive electrical conductivity between the neurons in the brain during seizures.
Phenytoin levels are affected by a number of factors including liver function, other drugs, levels of plasma proteins that form complex with it, and the age of the patient. Since phenytoin levels need to be maintained within a very narrow therapeutic range in blood, they are monitored regularly during treatment.
Preparation for Phenytoin
- No special preparation required
Sample Type for Phenytoin
Interpreting Phenytoin results
10 to 20 µg/ml (Children and adults)
8 to 15 µg/ml (Newborns)
Free phenytoin: 1 to 2 µg/ml
The therapeutic range of phenytoin may vary from person to person and depends on a number of other factors. Hence, the therapeutic range is established for the patient at the beginning of treatment.
Lower than the therapeutic range phenytoin concentration makes the drug ineffective in treatment.
Higher than the therapeutic range phenytoin concentration induces symptoms associated with phenytoin toxicity.
Answers to Patient Concerns & Frequently Asked Questions (FAQs) about Phenytoin
Frequently Asked Questions about Phenytoin