biotilgengeligheten

Biotilgengeligheten, or bioavailability, refers to the fraction of an administered dose of an unchanged drug that reaches the systemic circulation. This concept is crucial in pharmacology and medicine, as it determines the extent and rate at which an active substance becomes available at its site of action. Factors influencing bioavailability include the route of administration, the drug's formulation, its chemical properties, and individual patient characteristics.

For intravenous administration, bioavailability is generally considered 100%, as the drug is directly introduced into the bloodstream. However, for other routes, such as oral, topical, or intramuscular, bioavailability can be significantly lower. The oral route, for instance, is subject to absorption from the gastrointestinal tract, metabolism in the gut wall and liver (first-pass metabolism), and interactions with food.

Understanding a drug's bioavailability is essential for determining the correct dosage and dosing frequency to achieve therapeutic efficacy and minimize toxicity. Different formulations of the same drug can exhibit varying bioavailabilities, leading to differences in their clinical effects. Generic drugs are required to demonstrate bioequivalence to their brand-name counterparts, meaning they achieve the same bioavailability. Pharmacokinetic studies are designed to measure and assess a drug's bioavailability, providing vital data for drug development and clinical practice.