bioavailabilitythe

Bioavailability is the fraction of an administered dose of unchanged drug that reaches the systemic circulation. By definition, the bioavailability of an intravenously administered drug is 100%, since the drug is delivered directly into the bloodstream. For other routes, such as oral or transdermal, bioavailability is typically lower because of incomplete absorption and first-pass metabolism in the gut and liver.

A broad set of factors influences bioavailability. Route and formulation are primary determinants, including solubility, permeability across the intestinal lining, and the drug’s stability in the gastrointestinal environment. Food, gastric pH, and interactions with other drugs or nutrients can increase or decrease absorption. Individual factors such as age, health status, genetics, and concomitant diseases also contribute to variability in bioavailability.

Pharmacokinetically, absolute bioavailability compares a non-intravenous route with IV administration, while relative bioavailability compares two non-IV routes. It is commonly quantified using the area under the plasma concentration–time curve (AUC) and dose information: F equals AUC non-IV multiplied by Dose IV, divided by AUC IV multiplied by Dose non-IV. F is a dimensionless fraction that ranges from 0 to 1 (0% to 100%).

In pharmaceutical development, improving oral bioavailability is a major goal and may involve solubility enhancement, prodrugs, lipid-based formulations, nanoparticle carriers, or permeation enhancers. In nutrition, bioavailability also refers to the proportion of a nutrient that is absorbed and utilized in the body. Note: the term bioavailabilitythe appears to be a misspelling of bioavailability, which is the standard term used in scientific literature.