Page 141 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

The extent of protein binding depends on:

▪ physiochemical properties of the drug.

▪ the concentrations of drug and proteins in the plasma.
▪ the presence of other protein-bound drugs.

Changes in the binding characteristics of a drug could affect pharmacologic

response to the drug.

 In most patients: ▪ In patients with low serum
the free phenytoin concentration is albumin concentrations:

approximately 10% of the total
▪ a lower fraction of phenytoin is
concentration
bound to protein, and
▪ the free portion is up to 20% of
the total concentration.

▪ With hypoalbuminemia, a patient with a total phenytoin concentration of

15 mg/L may experience side effects (nystagmus and ataxia) usually seen at

a total concentration of 30 mg/L.

▪ In these patients, a lower total phenytoin concentration may control

seizures.

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