Plasma protein binding

Plasma protein binding refers to the degree to which medications attach reversibly to blood proteins—primarily albumin, alpha-1-acid glycoprotein, lipoproteins, and globulins—within the blood plasma. This process is not itself a molecular target but rather a key pharmacokinetic property that influences how much of a drug remains unbound ("free") and thus available for therapeutic action, metabolism, and excretion. Only the unbound fraction of most drugs is pharmacologically active; the bound portion acts as an inactive reservoir that can prolong half-life by slowly releasing drug into circulation[1][3][9]. The extent of plasma protein binding affects drug distribution volume, clearance rate, dosing regimen requirements, and risk for interactions or toxicity if displaced by other compounds or altered by disease states[2][6][8]. Plasma protein binding does not produce physiological effects directly nor represent an actionable therapeutic target; instead it modulates how drugs reach their actual targets within tissues[5]. Note: "Plasma protein binding" is not itself a receptor or molecule but describes an interaction between many different proteins and various drugs. It should not be considered as a canonical therapeutic target. If you are seeking information on specific plasma proteins involved in this process (e.g., human serum albumin), those would be appropriate targets with their own structured data entries.

Not applicable (not a molecular target, but a pharmacokinetic property)