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Volumes of distribution

Note that this chapter relates to the in vivo imaging with radioligands, and does not directly comply with the term volume of distribution in pharmacology.

Volume of distribution (V_T) of a radioligand is defined as the ratio of the radioligand concentration in tissue target region (C_T, kBq·cm^-3) to that in plasma (C_P, kBq·mL^-1) at equilibrium. C_P represents the concentration of parent radioligand in plasma, that is plasma concentration that is corrected for any radioactive label-carrying metabolites.

V_T = C_T / C_P

Therefore, a V_T equal to 15 mL·cm^-3 means that the radioligand is being concentrated in tissue by 15:1.

Tissue may contain radioligand that is specifically bound to receptors (S), non-specifically bound to other macromolecular components (NS), or free in tissue (FT) dissolved in water:

C_T = C_S + C_NS + C_FT

V_T = V_S + V_NS + V_FT

Volume of distribution in pharmacology

Distribution volume of a drug refers to the volume of plasma that would be required to account for the amount of drug in the entire body. Thus, the units of pharmacological volume of distribution are volumes, for example litre (L).

References:

Innis RB, Cunningham VJ, Delforge J, Fujita M, Gjedde A, Gunn RN, Holden J, Houle S, Huang SC, Ichise M, Iida H, Ito H, Kimura Y, Koeppe RA, Knudsen GM, Knuuti J, Lammertsma AA, Laruelle M, Logan J, Maguire RP, Mintun MA, Morris ED, Parsey R, Price JC, Slifstein M, Sossi V, Suhara T, Votaw JR, Wong DF, Carson RE. Consensus nomenclature for in vivo imaging of reversibly binding radioligands. J Cereb Blood Flow Metab. 2007; 27(9): 1533-1539.

Slifstein M, Laruelle M. Models and methods for derivation of in vivo neuroreceptor parameters with PET and SPECT reversible radiotracers. Nucl. Med. Biol. 2001; 28: 595-608.

Volumes of distribution

Volume of distribution in pharmacology

See also:

References: