While there is no limit to how large a Vd can be, it cannot be smaller than the volume of A or plasma in man. I depicts the relationship between Vd and the extent of distribution. The values represented there can be used to approximate the extent of a drug distribution. In total body fluids. Protein Binding Proteins are large molecules capable of attracting and binding smaller molecules.
Plasma proteins circulate in the body while other proteins are somewhat stationary.
A given drug, however, may have similar extent of binding to proteins in both sites. In plasma, acidic drugs tend to bind mainly to albumin while basic compounds have greater affinity towards alpha acid glycoproteins.