Is Dilantin weight based?

In general, phenytoin is dosed based on ideal (aka lean) body weight.

When should phenytoin levels be drawn?

Levels can be drawn at the point of admission, regardless of the patient’s normal dosing time. In normal healthy subjects after dose adjustment, the phenytoin level should be drawn within six to seven days with subsequent doses of phenytoin adjusted accordingly.

How do you titrate phenytoin?

If the phenytoin concentration is < 7 mcg/mL, the dose may be increased by 100 mg/day. If the phenytoin concentration is 7-12 mcg/mL, the dose may be increased by 50 mg/day. If the phenytoin concentration is >12 mcg/mL, the dose may be increased by 30 mg/day.

What is corrected phenytoin level?

Corrected phenytoin levels were calculated using the Sheiner-Tozer equation. Corrected phenytoin levels = Measured total phenytoin(micromol/l) [(albumin g/1 x 0.9)+ 0.1] 40. Results: At Visit 1, mean serum albumin levels were 44.1 +/- 1.1 micromol/l and mean serum phenytoin levels were 33.9 +/- 2.8 g/l.

How do you calculate phenytoin Vmax?

The concentration at steady state can be estimated using the following equation if Vmax and Km are known (may use population averages if not available): Css = [Km x (S) x (F) x dose(mg/day)] / [Vmax – (S)(F)(dose(mg/day))]. To simplify further steps, Daily dose will be abbreviated: dd.

Is phenytoin zero order kinetics?

Phenytoin follows nonlinear (or zero-order) kinetics at therapeutic concentrations, because the rate of metabolism is close to the maximum capacity of the enzymes involved. In nonlinear kinetics, clearance and half-life fluctuate with plasma concentration.

How do you interpret phenytoin levels?

Toxic phenytoin levels are defined as greater than 30 µg/mL. Lethal levels are defined as greater than 100 µg/mL. The reference range of free phenytoin is 1-2.5 µg/mL. In patients with renal failure associated with hypoalbuminemia, free phenytoin levels may be more accurate than total phenytoin levels.

When do you draw a peak and trough?

A trough level is drawn immediately before the next dose of the drug is administered. A peak level is drawn 1 to several hours after the drug is administered (depending on the drug).

What is trough and peak level?

The trough level is the lowest concentration in the patient’s bloodstream, therefore, the specimen should be collected just prior to administration of the drug. The peak level is the highest concentration of a drug in the patient’s bloodstream.

Do you need to monitor phenytoin levels?

Phenytoin blood testing is ordered because phenytoin blood levels must be maintained within a narrow therapeutic range. If levels are too low, the affected person may experience seizures; if they are too high, the person may experience symptoms associated with phenytoin toxicity.

What is a sub therapeutic level for Dilantin?

Although the reference range is between 10 and 20 µg/mL, about half of patients’ seizures are controlled at values lower and higher than the therapeutic range. Some adverse effects of phenytoin are related to specific serum levels. Nystagmus is frequently observed at levels greater than 20 µg/mL.