What does the term "bioavailability" refer to?

The term "bioavailability" refers to the proportion of a drug that enters circulation when it is introduced into the body. This measurement is crucial in pharmacology because it helps to determine how much of the administered dose reaches the systemic circulation and is available for therapeutic effect. Understanding bioavailability is essential for assessing the effectiveness of different routes of drug administration.

For instance, a drug administered intravenously has 100% bioavailability because it goes directly into the bloodstream, while oral medications may have lower bioavailability due to factors like metabolism in the liver or incomplete absorption in the gastrointestinal tract. Evaluating bioavailability can guide healthcare professionals in selecting the appropriate drug formulation and dosing strategy to achieve the desired therapeutic outcomes.