The degree to which a drug or other substance becomes available to the target tissue after administration.
The proportion of a substance that, once entered into the body’s circulation, is effectively used for biological activity.
Fraction of an ingested nutrient that is absorbed and used for a defined function in the body.
The extent to which any nutrient in foods is available for use by the body.
The extent and rate of absorption of a dose of a given drug, measured by the time-concentration curve for appearance of the administered drug in the blood. The concept is important in attempting to determine whether different brand name drugs, a generic name as opposed to a brand name drug, or, hi some cases, different batches of the same brand name drug, will produce the same therapeutic effect. The same drug made by two different manufacturers or different batches of the same drug made by the same manufacturer may demonstrate differing bioavailability. There is controversy as to whether such differences are therapeutically significant.
The extent to which a nutrient or medicine can be taken up by the body.
Quantity of nutrient available to the body after absorption. Bioavailability is a particular concern in the absorption of essential minerals. In this setting, bioavailability is defined as the percent of the consumed mineral that enters via the intestine and is used for its intended purpose.
The amount of a nutrient utilized from the diet for function within the body is used to describe the nutrient’s bioavailability.
The extent to which a drug reaches the systemic circulation following administration by various routes.
Readiness of a drug to produce an effect in the circulation at the target site.
The degree to which a drug or other substance is absorbed; the fraction of the oral drug that reaches central blood circulation. Bioavailability measures the extent to which a drug or dietary supplement becomes available to work on the body tissue after it is taken.
Bio-availability refers to the proportion of a drug reaching the circulation after a dose or doses have been given. The most important factor is first-pass metabolism — that is, destruction of all or part of the drug in either the intestine or the liver before it can get into the blood stream generally. Many fat-soluble drugs such as beta-adrenoceptor-blocking drugs (beta blockers), some tricyclic antidepressants, and various opiate analgesics are severely affected. Food may affect bioavailability by modifying gastric emptying, thus slowing drug absorption. Ingested calcium may combine with drugs such as tetracyclines, further reducing their absorption.
The rate and extent to which an active drug or metabolite enters the general circulation, permitting access to the site of action. Bioavailability is determined either by measurement of the concentration of the drug in body fluids or by the magnitude of the pharmacologic response.
The form in which nutrients can be broken down by the body and metabolized into easily-absorbed components.
The proportion of a therapeutic agent that can successfully reach and affect a particular bodily organ or tissue.
Nutrient bioavailability is an indicator of the body’s ability to absorb and utilize a given nutrient effectively.
The accessibility of certain chemical forms to organisms that inhabit a given environment.
Bioavailability refers to the proportion of a drug that reaches the intended organs and tissues, typically expressed as a percentage of the administered dose. When a drug is administered intravenously, it achieves 100 percent bioavailability since it is directly injected into the bloodstream. In contrast, drugs taken orally exhibit much lower bioavailability. Formulations with similar bioavailabilities are deemed bioequivalent.