Significance of Protein / tissue Binding of the drug.
Absorption-
The conventional dosage forms follow first order kinetics.
When there is more protein binding then it disturbs the absorption equilibrium.
Distribution-
A protein bound drug in particular does not cross the BBB, the placental barrier, or the glomerulus.
Thus protein binding decreases the distribution of drugs.
Metabolism-
Protein binding decreases the metabolism of drugs & enhances the biological half-life.
Only unbound fractions get metabolized.
e.g. Phenylbutazone & Sulfonamide
Elimination
Only the unbound drug is capable of being eliminated.
Protein binding prevents the entry of drugs to the metabolizing organ (liver ) & to glomerular filtration.
e.g. Tetracycline is eliminated mainly by glomerular filtration.
Systemic solubility of drug
Lipoproteins act as a vehicle for hydrophobic drugs like steroids, heparin, and oil soluble vitamins.
Drug action-
Protein binding inactivates the drugs because sufficient concentration of the drug can not be achieved at the receptor site for action.
e.g. Naphthoquinone
Sustain release-
The complex of drug proteins in the blood acts as a reservoir & continuously supplies the free drug.
e.g. Suramin sodium-protein binding for antitrypanosomal action.
Diagnosis-
The chlorine atom of chloroquine replaced with radiolabeled I- 131 can be used to visualize melanomas of the eye & disorders of the thyroid gland.
Commonly Asked Questions.
Give significance of protein binding of drugs.
Labels: Biopharmaceutics
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