Phenytoin Eptoin Dilantin Serum Test

Serum phenytoin levels are measured to ensure adequate therapy & diagnose overdose. It may also be used to check patient compliance. Initially, testing is done at regular intervals; to adjust the dose basis blood concentration in the first 5 days. Later on, the test is ordered at regular intervals and as needed to monitor blood concentrations.
Phenytoin clearance is affected by renal failure and hence drugs should be monitored closely in such cases

A phenytoin test determines the concentration of phenytoin in the blood. This drug has zero-order pharmacokinetics, and hence its clearance is dependent on its concentration in blood. The test helps determine the drug's blood level so that the proper dosage can be given. Seizures can occur if the levels are too low, so they must be strictly monitored. If the dose is too high, the person may experience symptoms of phenytoin poisoning.

The phenytoin test is done for the following reasons:

• Monitor the effectiveness of phenytoin treatment.
• Identify phenytoin drug overdoses.
• Assess patient compliance.
• Monitor the phenytoin levels in renal failure patients.

Testing is initially conducted at regular intervals during the first five days to modify the dose based on blood concentration. Later, the test is performed as needed at regular intervals to check blood concentrations.

Phenytoin test measures phenytoin concentration in blood. This drug has zero-order pharmacokinetics and hence its clearance is dependent on its concentration in blood

Phenytoin test requires a blood sample. A tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins. The skin is disinfected before needle insertion and the blood sample is collected in vacutainer

If Phenytoin levels are in the therapeutic range, it indicates that the patient is unlikely to have recurrent seizures and will not experience significant side effects. 
Results should often be evaluated in conjunction with the time of blood collection and dosage of medicine.
High levels may result in toxicity leading to nystagmus, ataxia, and dysarthria

If the patient's phenytoin levels are within the therapeutic range, they are unlikely to have recurrent seizures and will not experience any serious side effects. Results should be frequently assessed in conjunction with the timing of blood sampling and medication dosage. High levels can cause toxic effects such as nystagmus, ataxia (impaired coordination), and dysarthria (slurred speech).

• Patients who are taking phenytoin are closely monitored to make sure they are getting the right dose.
• Patients with signs of phenytoin poisoning, like dizziness, confusion, slurred speech, stiff muscles, occasional seizures, sleepiness, unsteadiness, and nystagmus (when the eyes move from side to side), have their phenytoin levels checked.
• Patients not responding to phenytoin treatment and showing recurrent seizures despite taking the drug.

The doctor will order this test for patients:

• taking phenytoin medication to monitor the right dose for treatment.
• showing symptoms of phenytoin poisoning like dizziness, confusion, slurred speech, muscle rigidity, occasional seizures, sleepiness, unsteadiness, and nystagmus (eye movement from side to side).
• unresponsive to phenytoin treatment and have recurrent seizures despite taking the drug.
• with renal failure, the phenytoin levels should be checked regularly.

After first initiating phenytoin intake, you should take the phenytoin test regularly for the first five days to arrive at the right dose. To ensure therapeutic efficacy and prevent toxicity, routine serum phenytoin concentration monitoring is required.

There is no need to fast or make any other particular preparations before the test.

A doctor might order other tests like -

• Complete blood count.
• Blood urea nitrogen and creatinine to assess kidney health.
• Liver function test
• Blood glucose test as phenytoin can increase your blood glucose.
• Serum sodium test
• Urine analysis

  A doctor might order other tests like -

• Complete blood count.
• Blood urea nitrogen and creatinine to assess kidney health.
• Liver function test
• Blood glucose test as phenytoin can increase your blood glucose.
• Serum sodium test
• Urine analysis