In order to know the meaning of the term bioavailability, it is necessary to begin by knowing its etymological origin. In this case, we can establish that it is the fruit of the sum of two clearly differentiated parts:
-The noun "bios", which can be translated as "life".
-The word availability that has a Latin origin and is the result of the union of these components: the prefix "dis-", which means "from top to bottom"; the verb "ponere", which is synonymous with "put"; the particle "-ible", which can be translated as "that can"; and the suffix "-dad", which comes to indicate "quality".
Bioavailability , word that the Royal Spanish Academy (RAE ) does not include in its dictionary, it is a term that refers to the speed Yet the quantity with which a drug is absorbed and reaches its action point in the organism
In other words, bioavailability refers to weather Yet the fraction with that the active principle comes to his therapeutic target (the site of the organism where it develops its actions). This bioavailability is reflected in the measurement in the blood of the parameters of the drug in question, from the levels that are reached in the systemic circulation of the individual.
The highest concentration of the active substance in the plasma or in the blood ; the time at which said concentration is recorded; and the area that exists under the plasma concentration curve with respect to time is the main parameters of bioavailability.
It can be said that bioavailability refers to the percentage of the active substance found in plasma. He Format of the medicine (capsule, tablet, etc.), the route of administration (oral, intravenous, topical) and others factors They make bioavailability vary.
Bioavailability, in this way, can demonstrate that the efficacy of a drug changes according to how it is delivered. The same amount of an active substance acts differently if it is administered as a capsule or if it is applied intravenously, to cite a possibility. This is because, before reaching the blood circulation and the site of action , the drug has to overcome several organic barriers that cause losses in the original dose.
In this sense we can establish that it is indicated that the injection of a drug has a bioavailability of 100% just after that. And it is that the active substance that it has has been administered directly through the blood.
Precisely for that reason, when it is a substance that is administered, for example, orally, bioavailability is reduced. Yes, it will be below 100%. That is because once the drug is introduced into the body through the mouth it has to pass through the esophagus, stomach and intestines.
In relation to the term at hand, we have to underline the existence of another that is used very frequently. We are referring to what is called bioequivalence. It is a term that is used to mention the relationship between two preparations of the same drug, with identical dosage and similar bioavailability.