Biokäyttöisyys

Biokäyttöisyys, often translated as bioavailability, refers to the rate and extent to which a substance, typically a drug or nutrient, is absorbed from its site of administration and becomes available at the site of action in the body. It is a crucial concept in pharmacology and nutrition, as it determines how effectively a substance can exert its intended effects.

For orally administered drugs, biokäyttöisyys is influenced by various factors. These include the drug's solubility and dissolution rate in the gastrointestinal fluids, its permeability across the intestinal wall, and its metabolism by enzymes in the gut wall and liver (first-pass metabolism). If a drug undergoes significant first-pass metabolism, a large portion of it can be inactivated before reaching the systemic circulation, thus reducing its biokäyttöisyys.

Other routes of administration, such as intravenous injection, bypass the absorption process entirely and achieve 100% biokäyttöisyys because the substance is directly introduced into the bloodstream. Topical and transdermal applications have varying biokäyttöisyys depending on the properties of the substance and the barrier it needs to cross. In nutrition, biokäyttöisyys describes how well the body can absorb and utilize nutrients from food. Factors like the food matrix, the presence of other dietary components, and individual physiological status can affect nutrient biokäyttöisyys. Understanding biokäyttöisyys is essential for determining appropriate dosages, optimizing drug therapy, and designing effective nutritional strategies.