Bioavailabilitya

Bioavailabilitya is not a standard term in pharmacology or nutrition and appears to be a misspelling of bioavailability. Bioavailability is the proportion of an administered substance that enters the systemic circulation and is available to exert an active effect. In pharmacology and nutrition science, bioavailability is a central concept for assessing how much of a drug, supplement, or nutrient becomes available to the body.

Absolute bioavailability refers to the fraction of an administered dose that reaches systemic circulation relative to intravenous administration. Relative bioavailability compares two non-intravenous formulations. Bioavailability is commonly expressed as a percentage and can be derived from pharmacokinetic measurements such as the area under the concentration-time curve (AUC) and peak plasma concentration (Cmax). The concept helps compare different dosage forms and routes of administration.

Factors influencing bioavailability include the route of administration (oral, intravenous, transdermal, etc.), formulation and solubility, stability in the gastrointestinal tract, and first-pass metabolism by the liver. Absorption is affected by gastric pH, presence of food, and interactions with other substances. Individual factors such as age, disease states, genetic differences in enzymes, and concomitant medications also contribute to variability in bioavailability. For nutrients, matrix effects and interactions with other dietary components can alter uptake.

Applications of bioavailability knowledge include optimizing drug formulations to improve efficacy and safety, guiding dosing regimens, and assessing the nutritional usability of supplements. Understanding bioavailability supports both pharmaceutical development and dietary planning, highlighting why the same substance can have different effects depending on its form and context. See also bioavailability concepts and pharmacokinetics.