Page 41 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

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

In this example:

 The beaker is considered like a human body,

 1 gm KI as the administered dose of a drug,

 Water is equivalent to the biological fluids.

 Charcoal is equivalent to the organs and tissues that are present in the body.

It is called an apparent volume because it is not a true physiologic volume; but

rather reflects the space the drug seems to occupy in the body.

The magnitude of the Vd may vary from a few liters (7 to 10 L) to several hundred

.
liters (200 L and higher) in a 70 kg subject
The higher the value of the Vd, the greater is the extent to which the drug is

distributed in the body tissues and or organs.

The value of the Vd also reflects the lipophilicity of a drug which, in turn, reflects

its chemical structure; because body tissues, biological membranes, and organs are

lipophilic in nature.

The Vd is a constant for a given drug and is independent of the administered dose

and route of drug administration.

40