Serum albumin and other plasma proteins

Serum albumin and other plasma proteins represent the collective group of proteins found in blood plasma, primarily synthesized in the liver. Albumin, the most prominent member, accounts for approximately 50-60% of total plasma protein and is essential for maintaining colloid osmotic pressure, which prevents fluid from leaking out of blood vessels (StatPearls, 2023). Beyond osmotic regulation, these proteins function as versatile carriers for endogenous molecules like bilirubin and fatty acids, as well as exogenous compounds including a wide variety of pharmaceutical drugs (UniProt P02768). In pharmacology, the binding of drugs to plasma proteins is a critical determinant of a drug's volume of distribution and half-life, as only the unbound fraction is typically capable of exerting a therapeutic effect or being metabolized (PubMed, PMC5394508). While these proteins are not usually the primary targets for disease-modifying therapies, they are vital for drug delivery systems, such as albumin-bound paclitaxel, and are administered directly in cases of severe volume depletion or liver failure. Monitoring their levels is clinically important, as hypoalbuminemia can lead to increased free drug concentrations and potential toxicity, particularly for highly protein-bound medications like warfarin (NIH, 2022). Changes in the concentration of these proteins due to disease states like cirrhosis or nephrotic syndrome can profoundly alter the pharmacokinetics and safety profiles of many therapeutic agents.

Other names

Plasma proteinsSerum proteinsBlood proteinsCirculating proteins

Drugs interact with these proteins primarily through reversible non-covalent binding to specific sites (e.g., Sudlow's sites I and II on albumin), which regulates the distribution, metabolism, and excretion of the drug by controlling its free concentration in the plasma (PubMed, PMC5394508).