Corrected phenytoin equation

How do you calculate corrected phenytoin?

If you are a human and are seeing this field, please leave it blank. If clcr < 20 mL/min then Corrected Phenytoin = Total Phenytoin Level / ( (0.1 x albumin) + 0.1) This is so cool!

When should phenytoin be corrected for albumin?

Corrects serum phenytoin level for renal failure and/or hypoalbuminemia. Use in patients with albumin ≤3.2 g/dL (32 g/L). The “Sheiner-Tozer Equation” is the official name of this correction.

What is free phenytoin?

The therapeutic ranges for most adults have been established at 10.0-20.0 mcg/mL for total phenytoin (bound plus unbound) and 1.0-2.0 mcg/mL for free phenytoin (unbound only). This reference range for unbound phenytoin (free) was established based on an assumed 10% unbound drug fraction.

How does albumin affect phenytoin levels?

Serum albumin concentrations < 3.5 g/dL have previously been shown to affect phenytoin binding ratios and to contribute to phenytoin intoxication. Decreased protein binding leads to an increase in the free fraction of the drug.

Why would phenytoin levels be low?

Patients with unusually low levels may be noncompliant or hypermetabolizers of phenytoin. Unusually high levels result from liver disease, congenital enzyme deficiency or drug interactions which result in metabolic interference.

What is phenytoin toxicity?

Dilantin, or phenytoin, toxicity happens when you have high levels of Dilantin in your body that become harmful. Dilantin is a medicine that is used to prevent and treat seizures. Dilantin toxicity can lead to a coma.

What can affect phenytoin levels?

Phenytoin interacts with a number of antiepileptic drugs: Carbamazepine, phenobarbital, valproic acid, sodium valproate can either increase or decrease phenytoin levels. Lamotrigine, valproic acid, topiramate, zonisamide and levetiracetam can all have their effect reduced by phenytoin.

How do you calculate corrected albumin?

Thus, the calcium level should be corrected in patients with low serum albumin levels, using the following formula: Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 – serum albumin [g/dL]), where 4.0 represents the average albumin level.

What does high phenytoin level mean?

The neurotoxic effects are concentration dependent and can range from mild nystagmus to ataxia, slurred speech, vomiting, lethargy and eventually coma and death. Paradoxically, at very high concentrations, phenytoin can lead to seizures. Symptoms correlate well with the unbound plasma phenytoin concentration.

What is phenytoin used for?

Phenytoin is used to control certain type of seizures, and to treat and prevent seizures that may begin during or after surgery to the brain or nervous system. Phenytoin is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in the brain.

Is phenytoin a level?

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.

What is a toxic Dilantin level?

Signs and symptoms of phenytoin toxicity typically correspond to the serum level, and progress from occasional mild nystagmus at 10-20 mcg/mL (the therapeutic range) to coma and seizures at levels above 50 mcg/mL (see Presentation and Workup). Treatment is supportive (see Treatment and Medication).

When should I take phenytoin?

It’s OK to take any form of phenytoin either with food or without food, but be consistent day in and day out. A person who usually takes it with meals should do that all the time. Don’t use more than the doctor prescribes. If one or two extra capsules are taken, call the doctor for advice.

What are the indications of an abnormal Phenytoin serum level?

Total phenytoin levels (mcg/mL) and typical corresponding signs and symptoms are as follows:Lower than 10 – Rare.Between 10 and 20 – Occasional mild nystagmus.Between 20 and 30 – Nystagmus.Between 30 and 40 – Ataxia, slurred speech, nausea, and vomiting.Between 40 and 50 – Lethargy and confusion.

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