What is bioavailability?

Bioavailability refers specifically to the fraction of an administered dose of unchanged drug that reaches systemic circulation. This concept is crucial in pharmacology because it helps determine how much of a drug is available to exert its therapeutic effect after administration. When a drug is administered, it undergoes various processes, including absorption and first-pass metabolism, which can significantly affect the amount that ultimately enters the bloodstream.

When considering how medications are delivered, whether orally, intravenously, or through other routes, bioavailability helps to elucidate the effectiveness and potency of these drugs. For example, intravenous administration generally results in 100% bioavailability, as the drug is delivered directly into the systemic circulation without the barriers presented in other routes (like the gastrointestinal tract).

By understanding bioavailability, healthcare professionals can better calculate dosing regimens and anticipate how quickly and effectively a drug will work within the body based on its delivery method. This knowledge directly impacts how medications are prescribed and managed in practice.