<P> Plasma protein binding refers to the degree to which medications attach to proteins within the blood . A drug's efficiency may be affected by the degree to which it binds . The less bound a drug is, the more efficiently it can traverse cell membranes or diffuse . Common blood proteins that drugs bind to are human serum albumin, lipoprotein, glycoprotein, and α, β ‚ and γ globulins . </P> <P> A drug in blood exists in two forms: bound and unbound . Depending on a specific drug's affinity for plasma protein, a proportion of the drug may become bound to plasma proteins, with the remainder being unbound . If the protein binding is reversible, then a chemical equilibrium will exist between the bound and unbound states, such that: </P>

What does it mean for a drug to be highly protein bound
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