Volume of Distribution

In pharmacokinetics , a branch of pharmacology , the volume of distribution (V _d , from the English Volume of Distribution), also known as the apparent volume of distribution , is the fictitious volume of a human or animal body in which a certain active ingredient or medicinal substance is located would have to distribute to explain the observed concentration in the blood plasma . The volume of distribution is to be understood as a pure calculation variable. It represents a quotient that relates the dose of an active ingredient administered to the concentration in the blood plasma:

${\displaystyle {Verteilungsvolumen}={\frac {\mathrm {Gesamtmenge\ des\ verabreichten\ Medikaments} }{\mathrm {Plasmakonzentration\ des\ entsprechenden\ Medikaments} }}}$

The unit for the volume of distribution is the liter , often given as liter / kg (normalized to body mass). Depending on the fat solubility ( lipophilicity ) or water solubility of an active ingredient, the volume of distribution in the same organism for different active ingredients can be of different sizes and can assume volumes that are significantly larger than the body volume.

Volumes of distribution play an important role in multi-compartment models of pharmacokinetics; A compartment has different properties, mainly a certain volume of distribution and clearance .

A distinction is made between the central volume of distribution ( ), in which a drug is quickly distributed after ingestion in the body, and the steady state volume of distribution ( ), which is taken after distribution in the body. The volume of distribution in the terminal end phase of elimination is referred to as. ${\displaystyle {V_{C}}}$ ${\displaystyle {V_{d}(SS)}}$ ${\displaystyle {V_{Z}}}$

literature

• Mutschler et al: Drug Effects: Textbook of Pharmacology and Toxicology. Scientific Publishing Company; 9th edition 2008