How do you calculate phenytoin levels?
Calculating for the corrected phenytoin level in patients with hypoalbuminemia. Corrected phenytoin level = reported level (mg/l) (mg/l) (0.9 x serum albumin (g/l) / 42) + 0.1 if the patient has hypoalbuminaemia (file size: A calculator for determining corrected phenytoin (albumin).
How do you load fosphenytoin?
Loading dose: 18 to 20 mg PE/kg IV Maintenance dose: 2 to 3 mg PE/kg IV dosed two times daily (4 to 6 mg PE/kg/day), though significantly higher dosing may be needed based upon levels. To decrease the risk of adverse reactions such as paresthesias, pruritus, and hypotension.
How fast can you run fosphenytoin?
The dose of IV fosphenytoin (15 to 20 mg PE/kg) that is used to treat status epilepticus is administered at a maximum rate of 150 mg PE/min. The typical fosphenytoin infusion administered to a 50 kg patient would take between 5 and 7 minutes.
What is the conversion of phenytoin to fosphenytoin?
1.5 mg of fosphenytoin sodium is equivalent to 1 mg phenytoin sodium, and is referred to as 1 mg phenytoin sodium equivalents (PE). The amount and concentration of fosphenytoin is always expressed in terms of mg PE.
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.
When do you get Fosphenytoin level?
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.
Is fosphenytoin the same as phenytoin?
Fosphenytoin, a phenytoin prodrug, has the same pharmacological properties as phenytoin but none of the injection site and cardiac rhythm complications of intravenous infusions of phenytoin.
How is fosphenytoin metabolized?
Fosphenytoin is metabolized, likely by phosphatases, to phenytoin, phosphate, and formaldehyde; the formaldehyde is subsequently converted into formate. The phenytoin produced is metabolized hepatically by CYP2C9 and, to a lesser extent, by CYP2C19.
How do you adjust fosphenytoin?
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.
Does Fosphenytoin need a filter?
Advantages of fosphenytoin over phenytoin include more rapid intravenous administration, no need for an intravenous filter, and a lower potential for local tissue and cardiac toxicity. Unlike phenytoin, fosphenytoin may also be administered by intramuscular injection.