What labs do you monitor for phenytoin?
What labs do you monitor for phenytoin?
Blood urea nitrogen and creatinine test to check kidney function. Liver function tests. Glucose test to measure your blood sugar, because phenytoin can cause your blood sugar to rise. Blood tests to measure the sodium level in your blood.
How do you calculate phenytoin levels?
Laboratories often report the value in g/L instead (g/dL = g/L x 0.1). After a patient has received a loading dose of intravenous phenytoin, levels can be checked one hour after the dose. If loading is achieved by oral dosing, phenytoin levels can be checked 24 hours after the last dose10.
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.
How do you convert mg dL to SI units?
To get from mg/dL to SI units, multiply by 0.01129.
When should Dilantin levels be checked?
A level can be taken 2-4 hours following an IV loading or top-up dose (12-24 hours for oral doses) and levels should then be monitored every 24 hours until control is achieved and concentration has stabilised.
What causes high phenytoin levels?
Phenytoin toxicity can occur from an increase in the daily dose of phenytoin, changes in the formulations or brands as well as changes in the frequency of administration. It can also occur when patients are started on new medications that interact with the metabolism or binding capacity of phenytoin to plasma proteins.
How do you calculate phenytoin Vmax?
Significant inter-patient variability may exist for many of the pharmacokinetic parameters. Here are some reported ranges: Vd: 0.52 – 0.78 L/kg Vmax: 6 – 8 mg/kg/day Km: 5.4 – 6.8 mg/L….Phenytoin dosing guidelines.
| Vmax | Maximum rate of drug metabolism |
|---|---|
| Km | Concentration at which the rate of drug metabolism is 50% of Vmax |
What calculation is used to correct total phenytoin levels for a low albumin concentration?
The “Sheiner-Tozer Equation” is the official name of this correction. This updated formula uses an albumin coefficient of 0.275, and 0.2 for patients with renal failure (see Evidence for details).
How do you convert triglycerides?
Conversion for TG (triglycerides) is calculated differently:
- To get from mmol/L to mg/dL multiply by 88.57 .
- To get from mg/dL to mmol/L multiply by 0.01129 .
What is the difference between ng/mL and pg mL?
pg/mL↔ng/ml 1 ng/ml = 1000 pg/mL. pg/mL↔g/dL 1 g/dL = 10000000000 pg/mL.
Why do we check Dilantin 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 Dilantin lab?
The Phenytoin Test is used to test for phenytoin, which is useful in generalized tonic-clonic, complex partial, and simple partial seizures and frequently is chosen for initial therapy, particularly in adults.
How do you calculate the correct phenytoin level?
It is recommended to contact pharmacy (ward pharmacist or on-call pharmacist) for advice on correcting the level however the following equation can be used: Corrected Phenytoin Level = (mg/L) reported level (mg/L) (0.9 x serum albumin (g/L) / 42) + 0.1 If the patient has hypoalbuminaemia (<35g/L) and a CrCl < 20mL/min
What are normal phenytoin and albumin levels?
THE BIG POD: Phenytoin Levels. We do this by checking both free (aka unbound) and total (aka unbound AND bound) levels. In a patient with normal albumin levels, goal total phenytoin levels are 10-20 mcg/mL . This is based on the fact that we want our free (therapeutically active) levels to be between 1-2 mcg/mL,…
What is the goal total and goal free phenytoin levels?
Goal Total Phenytoin Level: 10 – 20 mcg/ml (assuming normal albumin) Goal Free Phenytoin Level : 1 – 2 mcg/ml ( for both normal and abnormal albumin ) Now if a patient does NOT have normal albumin levels and/or has drug interactions that can affect protein binding of phenytoin, then your goal total levels will change.
What are the limitations of phenytoin?
Phenytoin has a narrow therapeutic index and has non-linear kinetics. This can result in difficulties in dose adjustment and interpretation of levels. A small change in dosing can result in a large change in blood levels.
