Volume of distribution

In pharmacology, the volume of distribution (${\displaystyle V_{D}}$, also known as apparent volume of distribution or volume of dilution^[1]) 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.^[2]

Roughly speaking, the ${\displaystyle V_{D}}$, as a property of a drug, measures the degree to which it is distributed in body tissue rather than the blood plasma. Drug properties which cause high ${\displaystyle V_{D}}$ include high lipid solubility (non-polarity), low rates of ionization, or low plasma protein binding capabilities. Disease states which increase ${\displaystyle V_{D}}$ include kidney failure (due to fluid retention) and liver failure (due to altered body fluid and plasma protein binding). Conversely, dehydration may decrease ${\displaystyle V_{D}}$.

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