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An Explanation of Bioavailability

   

In the extensive field of pharmacology, the concept of bioavailability or BA is seen as a subcategory of absorption and is also a fraction of what is known as the administered dose of an unaltered or unchanged drug. This drug will reach the systemic circulatory system, which is one of the main pharmacokinetic characteristics or properties of drugs. When you break it down, if you look at medication which is administered intravenously, the medication will have a bioavailability of 100%. If a medication is administered, however, in other ways or via other routes (for example, orally), the bioavailability will decrease. This is due to the first pass metabolic rate, as well as uncompleted absorption. This varies with each patient. This concept is one of the most important tools you will find in pharmacokinetics and must be considered when dosages for non-intravenous administrations of medications are determined.

Bioavailability will usually designate only the quantity or the fraction of the dose that is ingested and absorbed for dietary supplements that are almost always administered orally. These will include things like herbs and other dietary nutrients. This is slightly different when it comes to drugs that are administered by means other than orally. The food and drug administration regulations will also have an impact on how drugs are administered and the bioavailability of these drugs.

Related to the concept of bioavailability is bio-accessibility, which is kept in the context of environmental pollution as well as biodegradation. A molecule will be considered bioavailable when this molecule is available or able to cross a certain organism's cellular membrane from the surrounding environment should this organism has access to whichever chemical is in question.

Many physiological factors will influence and reduce the bioavailability of drugs before they even enter a system and are circulated within a system. If the drug is taken with food, it will affect the absorption rate. The speed of a metabolism as well as the concept of "first-pass metabolism" will have an affect on availability. The degree to which chemicals degrade will be affected by dissolution and diseases within the liver will also play a part.

 

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