Question

3. A dialysis patient taking phenytoin 300 mg daily has a total phenytoin concentration of 10 mg/L and a free level of 3 mg/L. What is his goal total level in order to keep his free level in the therapeutic range? What changes do you recommend to his dose? Please write your recommendation for any dose change needed to achieve the target level. (6 points)

Answer 1

Phenytoin is a drug used to prevent and control seizures coming under the classification of anticonvulsant or antiepileptic drug.

Monitoring of free Phenytoin concentrations may be beneficial in patients who is receiving dialysis.

Phenytoin metabolizes by the hydroxylation in the liver (CYP2C9,2C19)and the metabolism is saturable.

Phenytoin is excreted by extensive excretion through bile.

Phenytoin bioavailability is 1.

Here the dialysis patient is taking a total Phenytoin concentration of 10mg/L and a free level of 3mg/L.and taking 300mg daily.

The free phenytoin level is 3mg/L.The therapeutic concentration range for free Phenytoin in the body is 1-2.5mg/L.

Here the free Phenytoin level is 3mg/L,we have to consider for the concern or evidence for toxicity

Here in case the patient may experience drug toxicity or if the total drug concentration is within the therapeutic range.

Here the patient is receiving dialysis thus therefore the free phenytoin level is here is 3mg/L..Here the phenytoin plasma binding capacity can be alter here due to the present renal disease.

In this condition the plasma binding capacity can be alter due to displacement by endogenous compounds due to renal dysfunction.

Here the decreased phenytoin binding capacity is altered is decreased due to decreased apparent affinity for albumin may be due to accumulation of a substance "uremic toxin" which displaces phenytoin.Here we can see the effect of renal failure on phenytoin V_d

Here the correction factor is 0.2