In pharmacology, the volume of distribution, also known as apparent volume of distribution or volume of dilution) is the theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.

include kidney failure (due to fluid retention) and liver failure (due to altered body fluid and plasma protein binding.

The initial volume of distribution describes blood concentrations prior to attaining the apparent volume of distribution and uses the same formula.

Motivation and equation

Suppose one administers an amount of drug intravascularly, then measures the drug concentration in blood (assuming enough time has elapsed for the drug to distribute, but not enough time for elimination). The volume of distribution is the quotient:

value corresponding to a greater tendency for the drug to exit the intravascular space.

for that drug is known.

is not a physiological value; it is more a reflection of how a drug will distribute throughout the body depending on several physicochemical properties such as solubility, charge, size, etc.

may be reported extensively in litres (for a patient of given weight), or intensively as litres-per-kilogram.

may also be used to determine how readily a drug will displace into the body tissue compartments relative to the blood:

Where:

• : plasma volume

• : apparent tissue volume

• : fraction unbound in plasma

• : fraction unbound in tissue

Examples

For example, chloroquine .

References

External links

• Tutorial on volume of distribution

• Overview at icp.org.nz

• Overview at cornell.edu

• Overview at stanford.edu

• Overview at boomer.org