What does bioavailability refer to?

Bioavailability refers to the degree to which a drug is absorbed and utilized by the body. This concept is crucial in pharmacology because it determines how much of the active drug reaches systemic circulation after administration and is available for therapeutic effect. Factors such as the route of administration (oral, intravenous, etc.), formulation, and characteristics of the drug itself (solubility, stability, etc.) can all influence bioavailability.

For instance, medications that are taken orally must first pass through the digestive system and liver, where they might be partially metabolized before entering the bloodstream. In contrast, intravenous drugs directly enter systemic circulation, typically resulting in higher bioavailability. Understanding bioavailability is essential for determining appropriate dosing and expected efficacy of a medication.