Plasma protein binding

Plasma protein binding refers to the degree to which medications attach to proteins within the blood plasma. The degree to which drugs bind to these proteins can affect how they are distributed within the body and eliminated from it.

Overview

When a drug is ingested, it often binds to plasma proteins in the bloodstream. The most common proteins that drugs bind to are albumin, lipoprotein, glycoprotein, and globulin. The portion of the drug that is not bound to protein remains free in the bloodstream and can exert a therapeutic effect.

Importance

The degree of plasma protein binding is an important aspect of pharmacokinetics, as it can affect both the distribution and elimination of the medication. Drugs that are highly protein-bound are largely confined to the vascular system and are not readily distributed to body tissues.

Factors affecting plasma protein binding

Several factors can affect the degree of plasma protein binding. These include the concentration of the drug, the presence of other drugs, and the patient's physiological state. For example, conditions such as malnutrition, kidney disease, and liver disease can alter the levels of binding proteins in the blood, thereby affecting drug distribution and elimination.

Clinical significance

Understanding the degree of plasma protein binding, and the factors that can alter it, is important in the prescribing and dosing of medications. For example, if a drug is highly protein-bound and the patient has a condition that decreases the level of binding proteins, then the drug may be distributed more widely in the body, potentially leading to increased effects or side effects.

See also

• Pharmacokinetics
• Pharmacodynamics
• Drug metabolism