bioavailabilityit

Bioavailability refers to the fraction of an administered dose of an unchanged drug that reaches the systemic circulation. It is a key parameter in pharmacokinetics, describing the extent and rate at which a drug becomes available at its site of action. For intravenously administered drugs, bioavailability is considered 100% because the entire dose directly enters the bloodstream. However, for other routes of administration, such as oral, topical, or transdermal, bioavailability is often less than 100% due to factors like absorption barriers, first-pass metabolism in the liver, and drug degradation in the gastrointestinal tract. The rate of absorption also contributes to bioavailability, influencing how quickly the drug reaches therapeutic levels. Understanding bioavailability is crucial for determining appropriate dosage regimens and ensuring the efficacy and safety of medications. Different formulations of the same drug can also exhibit varying bioavailability.