Abstract Bioavailability, the degree and rate at which a substance is absorbed into the bloodstream and becomes available to its target site of action, is a critical factor in the efectiveness of medications and the utilization of nutrients. This article provides an overview of bioavailability, exploring the factors that influence it, including the route of administration, chemical characteristics of the substance, and individual variations in metabolism. The route of administration plays a ... Hence, the bioavailability of all other formulations and routes of administration can be compared to this reference value as an absolute standard, and from this the equation for absolute bioavailability can be derived: The absolute bioavailability then is the dose-corrected area under the curve (AUC) non-intravenous divided by AUC intravenous. The fraction of drug reaching the systemic circulation is expressed as the bioavailability. The concept of bioavailability is important in practice because the clinician can use routes of administration that maximize bioavailability. Bioavailability refers to the extent a substance or drug becomes completely available to its intended biological destination (s).
